Details of a Researcher - Takahashi, Hidetoshi

Papers - Takahashi, Hidetoshi

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Triaxial Microforce Plate Array for Measuring Reaction Force Distribution of Ants Walking on Ground and Wall

T Shiratori, H Takahashi

2026 IEEE 39th International Conference on Micro Electro Mechanical Systems … 2026

Sensor System for Gas Source Localization Integrating A Compact 3D Wind Vector Sensor and Gas Sensor

R Ando, H Takahashi

2026 IEEE 39th International Conference on Micro Electro Mechanical Systems … 2026

Acoustically driven MEMS mirror enhanced by a parallel Helmholtz resonator array

M Fukuta, R Nakashima, T Kan, H Takahashi

Journal of Micromechanics and Microengineering 2026

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Dual-Axis Acoustically Driven Mems Mirror with a Parallel Double-Layered Helmholtz Resonator Array

M Fukuta, H Takahashi

2026 IEEE 39th International Conference on Micro Electro Mechanical Systems … 2026

Optimizing resolution in force plate using the sampling moiré method

O Nomura, A Ogawa, H Takahashi

Japanese Journal of Applied Physics 2026

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Piezoresistive cantilever for in-plane force measurement using liquid-immersion laser sidewall doping

R Nakashima, Y Okamoto, Y Takei, T Kan, H Takahashi

Journal of Micromechanics and Microengineering 2026

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Two-axis transparent force plate for droplet collision measurement using high speed line-scan camera and sampling moiré method

Y Nakahara, T Shiratori, C Lee, YJ Heo, H Takahashi

IEEE Sensors Journal 2026

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Simultaneous Measurement of Contractile Force and Ca2+ Concentration Distribution in Human iPS Cell-Derived Cardiomyocytes

Ryota Ikegami, Takuya Tsukagoshi, Kenei Matsudaira, Hidetoshi Takahashi, Thanh-Vinh Nguyen, Kentaro Noda, Ken’ichi Koyanagi, Isao Shimoyama

Sensors 2025.12

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Simultaneous Measurement of Contractile Force and Ca2+ Concentration Distribution in Human iPS Cell-Derived Cardiomyocytes

Ikegami R., Tsukagoshi T., Matsudaira K., Takahashi H., Nguyen T.V., Noda K., Koyanagi K., Shimoyama I.

Sensors 25 ( 24 ) 2025.12

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) hold significant promise for regenerative medicine but exhibit immaturity relative to native cardiomyocytes. To make hiPSC-CMs more similar to mature cardiomyocytes, extensive research is being conducted from biochemical, electrochemical, mechanical, and physical perspectives. Quantitatively assessing their maturation is essential to evaluate improvements in cardiac cell function and clarify the impact of previous research. In this study, we present a high-speed sensing system that enables simultaneous, real-time measurement of cardiomyocyte contractile force, and intra- and extra-cellular Ca2+ dynamics. To enhance measurement precision, a visualization technique is incorporated to identify individual cardiomyocytes. This simultaneous evaluation system for cardiomyocyte contractility and various ion concentrations has the potential to become an effective and powerful foundational technology for assessing cardiomyocyte maturation and the regenerative medicine applications of IPSC-CMs. The ability to convert cardiomyocyte contractile force into single-cell force implies a more universal evaluation of the mechanical properties.

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Laser-Based Fabrication of Piezoresistive Cantilevers Utilizing Pulse Laser Annealing

Nakashima R., Kan T., Takahashi H.

Advanced Sensor Research 4 ( 11 ) 2025.11

Microelectromechanical system (MEMS) sensors based on piezoresistive elements are widely used in various applications due to their high sensitivity and compact size. Traditionally, silicon-based MEMS devices have been fabricated using lithography-based processes, with piezoresistive layers formed through thermal diffusion or ion implantation. However, these processes involve complex fabrication workflows. In response, laser fabrication techniques, such as laser micromachining and laser annealing-based impurity diffusion, have attracted attention. In this study, a laser-based approach for fabricating a silicon piezoresistive cantilever using nanosecond-pulse laser annealing is proposed. The proposed process integrates two steps: localized laser annealing for impurity doping and the formation of a partially 3D cantilever structure through laser cutting and etching. All the fabrication steps are performed using a single-laser processing system, enabling direct-write patterning and automatic alignment of the piezoresistive layer with the sensor structure without lithography. In this paper, the effectiveness of the proposed method is evaluated through electrical and mechanical characterizations of the fabricated sensor. The fabricated piezoresistive layer exhibits a gauge factor exceeding 15, indicating that the sensor is sufficiently effective for practical use.

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Laser-Induced Graphene Cantilever Airflow Sensor Fabricated via Laser Cutting and Folding a Copper–Polyimide Film

Ohara K., Ando R., Shimada K., Kishimoto T., Nakashima R., Takahashi H.

Advanced Sensor Research 4 ( 10 ) 2025.10

Various animals in nature, particularly insects, are equipped with sensory hair capable of detecting minute fluid forces. Inspired by these biological structures, numerous airflow sensors have been developed using Si-based microelectromechanical systems. However, the complexity of the fabrication process and difficulty in integrating shape-controlled sensing elements remain significant challenges. Laser-induced graphene (LIG) has attracted increasing attention as a promising material for various physical sensors, owing to its high piezoresistive sensitivity and simple fabrication process. Polyimide (PI), which is widely used as a substrate for LIG formation, exhibits thermoplastic properties that enable the straightforward creation of 3D structures. This study proposes a single-axis airflow sensor featuring a vertically standing LIG cantilever. The fabrication process involved only a fiber laser for cutting the PI film, forming the LIG-sensing elements, and folding the cantilever structure. The fabricated sensor measured 25 mm × 25 mm at the base and 10.5 mm high. The fabricated sensor integrated surface-mounted circuits within its base. Wind tunnel experiments demonstrate that the sensor exhibits a quadratic response to wind speeds between −10 and 10 m s−1. This approach offers promising prospects for the development of 3D LIG sensing elements for airflow sensors.

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Laser-Induced Graphene-Based Pressure Sensor With Corrugated Polyimide Diaphragm

Ryo Oda, Rihachiro Nakashima, Hidetoshi Takahashi

IEEE Sensors Journal 2025.03

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Multi-Inlet 2-D Water Flow Vector Sensor Using a Sealed Incompressible Liquid and Neural Network for Marine Biologging

Takuto Kishimoto, Kyota Shimada, Ryusei Ando, Kenei Matsudaira, Hiroto Tanaka, Hidetoshi Takahashi

IEEE Sensors Journal 25 ( 5 ) 8093 - 8105 2025.03

ISSN 1530437X

This study designed and demonstrated a 2-D multiinlet water flow sensor to address challenges associated with measuring the swimming speeds of marine animals owing to size limits and harsh marine environmental conditions, such as clogging by marine debris. The sensor comprises a spherical housing equipped with three pairs of inlets on opposite sides, each connected to a differential pressure sensor element through a tube filled with an incompressible liquid. Notably, a sealed film placed over each inlet prevents marine debris from intruding into the sensor. The differential pressure data collected by the three sensor elements are used to determine 2-D water flow speed and angle using a neural network (NN) trained on water tunnel experiments. The results of the experiments conducted in this study demonstrated that the developed sensor could accurately detect the water flow speed and angle within a speed range of 0.6-2.0 m/s, which is typical of green turtles. The proposed sensor is, therefore, expected to realize improved biologging of marine animal behaviors.

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Laser-induced graphene based pressure sensor with corrugated polyimide diaphragm

R Oda, R Nakashima, H Takahashi

IEEE Sensors Journal 2025

Influence of cantilever dimensions on time response characteristics of a MEMS piezoresistive-cantilever-based barometric pressure change sensor

T Kato, H Takahashi

Japanese Journal of Applied Physics 64 ( 5 ) 2025

ISSN 00214922

A barometric pressure change sensor utilizing a microelectromechanical system piezoresistive cantilever achieves high sensitivity and robustness. However, its miniaturization is constrained by the trade-off between the cutoff frequency of the mechanical high-pass filter and the air chamber volume. This study investigates the relationship between cantilever dimensions and their frequency characteristics. Experimental and theoretical results confirm that the frequency response varies with cantilever length and thickness. These findings contribute to optimizing these parameters, enabling miniaturization while maintaining high sensitivity and a low cutoff frequency.

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Biaxial Glass Force Plate using Inclined Laser Induced Backside Wet Etching through a Prism

N Ono, R Nakashima, T Shiratori, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 833 - 836 2025

ISSN 10846999

This paper reports a biaxial force plate designed to measure ground reaction forces in small insects. The device utilizes a glass spring structure to detect both vertical and shear forces, with two laser displacement meters for force capture. A V-shaped groove formed by fiber laser-induced backside wet etching through a triangular prism, allows precise biaxial force measurements. The proposed force plate structure can be fabricated entirely using laser beam processing. The fabricated force plate realized a force resolution of 0.37 μN, providing the significantly high sensitivity for fruit fly measurement.

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Bi-axial micro force plate utilizing dual laser displacement meters for ground reaction force measurement in fruit flies

N Ono, K Shimazaki, H Toda, H Takahashi

IEEE Sensors Journal 25 ( 10 ) 16821 - 16829 2025

ISSN 1530437X

The measurement of ground reaction forces (GRFs) is crucial for evaluating the gait mechanics of small insects, which can contribute to advancements in microrobots. Although a micro force plate capable of multi-axis measurement at the μN scale is desired to fully understand this mechanism, fabrication remains challenging. This study proposes a force plate capable of measuring both vertical and shear forces for a fruit fly, which can be constructed with relative ease. The proposed force plate is fabricated by laser processing, simultaneously producing a plate and its supporting spring structure, which facilitates displacement in the bi-axial directions. The plate displacement is measured using two laser displacement meters inclined at ±45°, directed toward a right isosceles triangular bump located at the plate center. Subsequently, the bi-axial forces are calculated based on Hooke's law. The fabricated force plate realized force resolutions of approximately 0.3μN in both directions, equivalent to 1/30 of a fruit fly's body weight. Finally, GRF measurements during fruit fly walking were successfully demonstrated using the fabricated force plate.

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Arrayed Electrical Stimulation Platform for Accurate Evaluation of Contractile Force of Ring-Shaped Engineered Heart Tissue

D Miyata, A Masuda, G Kagawa, H Tani, H Takahashi, S Tohyama, ...

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 83 - 86 2025

ISSN 10846999

This paper describes an arrayed culture device for ring-shaped microscale engineered heart tissues (rEHT) to acquire data on the effect of electrical stimulation for contractile force (CF). Elastic pillars in millimeter-scale culture space were fabricated accurately with a 3D printed mold, enabling rEHT formation with small number of cells (1.0×105 cells). Thus, our device is suited to the acquisition of accurate and large numbers of experimental data. Our device was verified by confirming rEHT's response to electrical stimulation and CF measurement from the pillar deflection. We believe that our device would match to explore the electrical stimulus effect for heart tissue maturation with an AI-driven optimization algorithm.

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Acoustically Driven Scanning Mirror Enhanced by Helmholtz Resonator Unit

M Fukuta, R Nakashima, T Kan, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 995 - 998 2025

ISSN 10846999

This paper presents a method for amplifying an acoustically driven MEMS scanning mirror by using a Helmholtz resonator (HR). One of the ways for driving MEMS scanning mirrors is the use of acoustic pressure. Here we propose to combine an HR array, whose resonant frequency matches the mirror's mechanical resonant frequency. The HR array is located between the acoustic source element and the mirror. Then, the HR array amplifies sound waves of the target frequency, and the resonance amplifies the mirror vibration. We fabricated a prototype mirror with a piezoresistor, and quantitatively evaluated the vibration amplitude. Experimental results confirmed that the HR amplified the vibration by a factor of approximately 20.

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2-Axis Force Plate for Droplet Collision Measurement using Line Scan Camera and Sampling Moiré Method

Y Nakahara, S Kato, H Onoe, C Lee, YJ Heo, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 821 - 824 2025

ISSN 10846999

This paper proposes a method to measure the 2-axis force of a droplet collision when it is dropped on the slope surface. To calculate the 2-axis small impact force at the same time, a force plate using the sampling moiré method with a line scan camera and a prism is employed. The sampling moiré method can precisely calculate the pattern's in-of-plane displacement. Moreover, both in-plane and out-of-plane displacements of the pattern are detectable utilizing a prism. Additionally, a line scan camera can capture 10k images in one second with 4096 pixels width, which is sufficient for high precision and high-time resolution displacement measurement.In this report, line&space patterns are attached to a glass plate, which is supported by four springs. The applied 2-axis force is calculated by multiplying the analyzed displacement and spring constant. We fabricated and calibrated the force plate system. It was confirmed that the force resolutions were less than 4 μN for the 2-axis. Finally, droplet collision experiments were conducted under several conditions. The force plate was able to measure impact force during oblique impact with 2-axis.

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Laser-Induced Graphene-Based Pressure Sensor with Corrugated Polyimide Diaphragm

Oda R., Nakashima R., Takahashi H.

IEEE Sensors Journal 25 ( 5 ) 8115 - 8123 2025

ISSN 1530437X

Until now, various types of pressure sensors, including piezoresistive and capacitive types, have been developed using the technology of microelectromechanical systems (MEMSs). However, many of these sensors require complex fabrication processes, making it challenging to form 3-D shapes. In contrast, laser-induced graphene (LIG) shows promise for use in various physical sensors due to its high sensitivity as a piezoresistive material and its simple fabrication process. Polyimide (PI) substrates, commonly used for LIG formation, can be easily grooved and cut by ultraviolet (UV) lasers, allowing for the fabrication of 3-D shapes. In this study, we propose a two-gauge corrugated-type pressure sensor with LIG strain gauges on both the top and back sides of a PI substrate featuring a corrugated structure. The fabrication process involves using a UV laser to fabricate the corrugated structure and a CO2 laser to form the LIG strain gauges. This simple process produced a sensor with dimensions of 10 mm in length, 15 mm in width, and a total thickness of 6 mm. The corrugated sensor deformed 1.8 times more under pressure and demonstrated three times greater sensitivity than the membrane-type PI sensor. This approach is effective for low low-volume production of a large variety of sensors in laboratories because it enables simple design and fabrication using only two types of lasers.

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Vibration-Based Airflow Sensor with Three-Dimensional Bluff Body Structure Formed Using Laser Folding Technique on Copper-Polyimide Film

K Ohara, R Nakashima, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 639 - 642 2025

ISSN 10846999

This paper proposes an airflow sensor based on galloping vibration. The proposed sensor consists of an upright laser induced graphene (LIG) cantilever with a three-dimensional (3D) bluff body on a copper-polyimide (Cu-PI) film. The entire fabrication process-including cutting, bending, Cu etching, and LIG formation, is carried out using a single fiber laser, resulting in compact bluff body structures and wiring. The fabricated sensor responded to wind speed with high stability.

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Three-axis force plate using high-speed line-scan camera and tilted pattern for sampling moiré method

Y Nakahara, O Nomura, T Shiratori, H Takahashi

IEEE Sensors Journal 25 ( 5 ) 8085 - 8092 2025

ISSN 1530437X

Force plates utilizing various principles capable of simultaneously measuring vertical and shear forces have been developed to analyze ground reaction force (GRF) in studies of animal locomotion mechanics. Recently, a triaxial force plate with high accuracy and measurement independence has been proposed using the sampling moiré (SM) method and a prism. The SM method can detect in-plane displacement of a pattern image with significantly higher accuracy than pixel size. However, with implementations using area-scan cameras, it was difficult to achieve both large number of pixels, which determine force resolution, and high frame rate, which affects temporal resolution. Here, we propose an SM method force plate with high accuracy and time resolution using a line-scan camera with a single vertical pixel, high horizontal resolution, and high frame rate. To realize three-axis force measurement from 1-D images, a pair of tilted patterns are utilized for SM method analysis. The fabricated force plate was calibrated and confirmed to have a force resolution of less than 35 mN for each axis and a positional error of less than 3%. Therefore, the proposed force plate can be useful for highly accurate GRF measurement with high frame rate capabilities.

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Switchable acoustic notch filter using a 3D-printed Helmholtz resonator array with bistable structures

M Fukuta, G Kagawa, H Takahashi

Extreme Mechanics Letters, 102333 77 2025

Acoustic noise is a significant environmental issue that affects quality of life, including in workplaces. Therefore, the ability to selectively block specific sound frequencies is desired to maintain clear vocal communication. Electrically driven active noise control (ANC) is a common solution. However, its effectiveness is limited to frequencies above 1 kHz. On the other hand, passive noise control (PNC) has gained attention as an alternative solution due to its non-reliance on electricity. Among these, Helmholtz resonators (HRs) have recently attracted interest due to their ability to reduce acoustic noise at their resonant frequencies. Traditional HRs are generally limited to attenuating single frequencies, which restricts their ability to attenuate multiple frequencies using a single device. Herein, we propose an HR featuring a bistable structure that enables switching between two distinct attenuation frequencies. A bistable structure with two stable states allows for switchable configurations that enable volume changes. By integrating this bistable mechanism into an HR chamber, the resonant frequency can be altered by changing the chamber volume. Consequently, the proposed HR can attenuate two different frequencies between the concave and convex states. The proposed system was fabricated using a 3D printer with silicone material, and its bistable properties were evaluated. The measured resonant frequencies were 6.6 kHz in the concave state and 4.1 kHz in the convex state, resulting in dual-frequency noise reduction. In principle, the proposed HR design can be extended to a multi-stable mechanism that enables the attenuation of multiple frequencies.

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Optical Cantilever Using Diffraction Grating and Sampling Moiré Method

S Sato, T Shiratori, T Kan, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 979 - 982 2025

ISSN 10846999

This paper reports an optical cantilever that can measure displacement with high resolution by using an interference pattern and the sampling moiré method. The proposed cantilever has a diffraction grating on its surface, and when light is incident on the surface, the interference pattern of diffracted light is reflected. As the cantilever is displaced downward, the pattern also moves. The shift of the pattern is analyzed by the sampling moiré method. The cantilever displacement was magnified by a factor of approximately 17 using the optical lever method. The experimental results confirmed that the proposed method functions as a high-performance optical cantilever.

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Multi-Inlet Two-Dimensional Waterflow Vector Sensor Using a Sealed Incompressible Liquid and Neural Network for Marine Biologging

T Kishimoto, K Shimada, R Ando, K Matsudaira, H Tanaka, H Takahashi

IEEE Sensors Journal 2025

Micro Force Plate Array for Measuring 3-Axis Ground Reaction Forces in Ants Using Sampling Moiré Method

T Shiratori, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 853 - 856 2025

ISSN 10846999

This paper reports on a micro force plate array for measuring the 3-axis ground reaction forces (GRFs) of small insects. Multipoint measurement of micro-force in 3-axis has been achieved by utilizing a prism and the sampling moiré method. The spring constant of each direction was several tens of N/m, and the force resolution in each direction was several tens of μN, which was sufficiently sensitive to detect ants. As a demonstration, an ant walked across the fabricated device, and the measurement of the 3-axis GRFs of the single leg was performed.

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Laser-Induced Graphene-Based Pressure Sensor with Corrugated Polyimide Diaphragm

Oda R., Nakashima R., Takahashi H.

IEEE Sensors Journal 25 ( 5 ) 8115 - 8123 2025

ISSN 1530437X

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Simultaneous Measurement of Contractile Force and Ca2+ Concentration Distribution in Human iPS Cell-Derived Cardiomyocytes

I Ryota, T Takuya, M Kenei, H Takahashi, N Thanh-Vinh, N Kentaro, ...

Sensors 25 (24), 7478 2025

Simultaneous Measurement of Contractile Force and Ca2+ Concentration Distribution in Human iPS Cell-Derived Cardiomyocytes

R Ikegami, T Tsukagoshi, K Matsudaira, H Takahashi, TV Nguyen, ...

Sensors 25 (24), 7478 2025

Triaxial micro force plate array for measuring ground reaction force in ant locomotion

T Shiratori, H Takahashi

IEEE Sensors Journal 25 ( 18 ) 34480 - 34490 2025

ISSN 1530437X

Terrestrial insects, such as ants, are known for their agile locomotion on six legs. However, the ground reaction force (GRF) of each leg has not been well characterized due to its difficulty in measurement. In this report, a micro force plate array is presented that uses the sampling Moiré (SM) method, a prism, and a single camera to simultaneously measure the triaxial GRFs of multiple legs of an ant during its locomotion. The SM method is a high-resolution measurement method that measures the amount of displacement based on the shift of a captured grid pattern. The proposed micro force plate array consists of a 3 × 3 array of 2900 × 2900 × 70 μm plate bases with a gap of 100 μm as the contact surface of the ant legs. The plate base is supported by a spring structure with a grid pattern. By capturing this grid pattern from the backside via a prism, a camera can capture images from two different directions, allowing the triaxial displacement to be measured. By dividing the plate surface into nine sections and evaluating the error based on the position of the force application in the z-direction force, a maximum measurement error of 6% was found. The average force resolution in the x-, y-, and z-directions for the nine plates was 3.34, 2.47, and 1.20 μN, respectively. With the developed force plate array, it was possible to measure the GRF of each leg simultaneously while the ant was walking.

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Biogenic Design of the Flexible, Resilient, and Hard Mineral Protector in Door Snails

Y Kurihara, T Yoshimura, I Häggmark, R Ueshima, M Hayama, ...

Small Science 5 (12), e202500385 5 ( 12 ) 2025

Organism design incorporates diverse materials with varying properties, such as hard skeletons of biogenic minerals and soft organic skins. However, achieving a balance of flexibility, resilience, and hardness remains a challenge even for organisms. Door snails have a calcareous door (clausilium) that covers the aperture. The clausilium combines hardness for defense and flexibility for opening and closing. Here, this work focuses on the biogenic design of a clausilium stalk as a unique architecture balancing several properties. This study investigates the stalk, a twisted ribbon with high flexibility and resilience, which is identified as a synapomorphic structure in 22 Clausiliidae species across seven subfamilies and 17 tribes. Internal observations reveal a double-layered structure: a hard, dense envelope with aragonite rods arranged in the b axis and a flexible, low-density core with randomly packed aragonite nanoparticles and organic matter. The anisotropic hierarchical design seen in nature is surely useful in the development of artificial materials that combine flexibility, resilience, and hardness.

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Fully invisible and unperceivable skin electrodes for facial physiological monitoring free from appearance artifacts

Y Liu, S Ito, T Kato, L Wang, Y Zhu, S De Mulatier, H Arao, S Suwazono, ...

ChemRxiv 2025 (0821) 2025

Seesaw-type force sensor with variable spring constant utilizing magnetic restoring force and external laser displacement measurement

S SATO, M ASAI, H TAKAHASHI

Mechanical Engineering Journal 12 (4), 25-00104-25-00104 2025

3-D Wave Measurement System Using IMU and MEMS Cantilever-Type Differential Pressure Sensor

K Shimada, T Kishimoto, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Arrayed Triaxial Force Plate System Using High-Speed Line-Scan Camera and Sampling Moiré Method

Y Nakahara, T Shiratori, H Takahashi

2025 IEEE SENSORS, 1-4 2025

Compact 3D Airflow Vector Sensor Using Multiple MEMS Differential Pressure Sensors and Neural Network-Based Estimation

R Ando, H Takahashi

2025 IEEE SENSORS, 1-4 2025

Corrugated Glass Diaphragm Differential Pressure Sensor Using Sampling Moiré Method

T Nakajima, O Nomura, R Oda, T Kishimoto, T Shiratori, K Shimada, ...

IEEE Sensors Letters 9 ( 10 ) 2025

Various types of pressure sensors have been developed because pressure monitoring is essential in a variety of fields. Among these, optical methods have attracted attention due to their high sensitivity and low drift; however, they often require complex setups. Recently, the sampling Moiré (SM) method has emerged as an optical measurement technique, offering both simplicity and high resolution. In this letter, we propose a vision-based differential pressure sensor using the SM method. The proposed sensor consists of a corrugated glass diaphragm with a stripe pattern, a right-angle prism, and a microcontroller-based board camera. From the images of the stripe pattern captured before and after diaphragm displacement, the applied differential pressure is calculated using the SM method. We designed and fabricated a corrugated glass diaphragm with a thickness of 50 µm using laser processing. A stripe pattern with a pitch of 0.4 mm was formed at the center of the diaphragm. Then, the sensor was fabricated by assembling the corrugated glass diaphragm, the prism, and the camera. The pressure calibration experiments were conducted to evaluate the sensor response. When a differential pressure of −200 to +200 Pa was applied to the sensor, the measured displacement was linear, with a resolution of less than 10 Pa. These results suggest that the proposed vision-based sensor can effectively measure differential pressure with a simple setup.

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Force Distribution Measurement of Plant Root Growth Using Gel Medium Embedded with Phosphorescent Beads and Sampling Moiré Method

G Kagawa, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Insect Antennae-Based Sensor for Simultaneous Airflow and Odor Measurement with Odor Concentration Estimation

R Ando, C Fukui, K Ohara, D Terutsuki, T Nakata, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Laser-Fabricated Piezoresistive Force Sensor with Liquid Immersion Laser Sidewall-Doping

R Nakashima, Y Okamoto, Y Takei, T Kan, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … (IEEE) 255 - 258 2025

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Laser‐Based Fabrication of Piezoresistive Cantilevers Utilizing Pulse Laser Annealing

R Nakashima, T Kan, H Takahashi

Advanced Sensor Research 4 (11), e00092 2025

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Laser‐Induced Graphene Cantilever Airflow Sensor Fabricated via Laser Cutting and Folding a Copper–Polyimide Film

K Ohara, R Ando, K Shimada, T Kishimoto, R Nakashima, H Takahashi

Advanced Sensor Research 4 (10), e00091 2025

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Micro Triaxial Force Plate Supported by Tilted UV-Curable PDMS Pillars with Isotropic Spring Constants via Liquid-Immersion Inclined Exposure

T Shiratori, G Kagawa, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Optical Cantilever for High-Resolution Displacement Measurement Using Diffraction Grating and Sampling Moiré Method

S Sato, T Shiratori, T Kan, H Takahashi

IEEE Sensors Journal 25 ( 15 ) 28119 - 28126 2025

ISSN 1530437X

Cantilever-type sensors play a critical role in precision measurement across various fields. Among the available detection principles, the optical lever method detects minute cantilever displacements via the reflection angle of a laser, achieving high-resolution displacement and force detection. Generally, a bi-cell or quadrant photodiode (PD) is used, and the reflected light must be initially positioned at the center. Additionally, if the reflected light moves beyond the dividing line of the PD, measurement becomes impossible. Conversely, the sampling moiré (SM) method has attracted attention for similar optical displacement measurement methods. The SM method enables high-resolution displacement measurement of the captured periodic pattern. The periodic pattern is captured in camera images, eliminating the need to adjust the light centered on PDs, and the detectable range of displacement in the sensing mechanism is not limited. This study proposes a measurement method that integrates the optical lever and the SM methods using a glass cantilever with a diffraction grating. When the cantilever is irradiated with laser light, the grating diffracts the reflected light at the cantilever surface, forming a diffraction pattern. As the cantilever is deformed, the diffraction pattern shift is captured by a camera and analyzed using the SM method, yielding the displacement value. In the experiment, the diffraction pattern spanning over approximately 200 μm was captured by a lens-less camera. With a cantilever displacement of 4 μm, the diffraction pattern captured by the camera shifted by 80 μm, corresponding to a 20-fold amplification of the cantilever displacement. The resolution of cantilever displacement, determined through an analysis of pattern shifts, was calculated to be under 3.5 nm. The proposed method offers a robust and adjustment-free technique for cantilever-type sensor measurements.

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Optical cantilever using diffraction grating and sampling moire method

S Sato, T Shiratori, T Kan, H Takahashi

2025 IEEE 38th International Conference on Micro Electro Mechanical Systems … 2025

Optical Cantilever Utilizing on-Chip Pattern Laser and Sampling Moiré Method

S Sato, T Shiratori, H Takahashi

2025 IEEE SENSORS, 1-4 2025

Robust Pitot-Type Waterflow Sensor System for Marine Animals in Harsh Environments

T Kishimoto, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Sampling moiré method triaxial force plate with metal three-dimensionally printed structure

O NOMURA, H TAKAHASHI

Mechanical Engineering Journal 12 (4), 25-00055-25-00055 2025

Sampling Moiré Method-Based Weight Scale Utilizing Dual-Pitch Stripe Pattern for High Resolution and Wide Range

M Kurihara, T Kishimoto, K Shimada, R Ando, O Nomura, T Shiratori, ...

IEEE Sensors Letters 9 ( 9 ) 2025

Continuous measurement of the body mass of seabird chicks during the nestling period is valuable for investigating their growth ecology. To periodically measure their body mass without excessive disturbance, weight scales have been installed inside nests that have been constructed previously. Conventional weight scales had difficulty with low output drift and maintaining low power consumption. A force plate utilizing the sampling Moiré (SM) method, achieving high resolution and drift robustness in human use, was proposed. An applied force was calculated from a displacement detected by analyzing the stripe pattern captured by a camera. However, if there is a change of more than half the pattern pitch between frames, it cannot be measured correctly. Then, we propose an SM method-based weight scale that can be installed in nests and is suitable for time-lapse measurements, reducing power consumption. The proposed weight scale comprises a top plate supported with springs, an optical prism, and a microcontroller-based camera board. A dual-pitch stripe pattern, incorporating both short- and wide-pitch components, is attached to the backside of the top plate. Plate displacement is measured by analyzing images of the stripe pattern captured through the prism. Correction of the short-pitch results using the long-pitch results resolves phase wrapping and enables both high resolution and a wide measurement range. Calibration experiments of the developed weight scale demonstrated that the dual-pitch approach measured weights up to 2 kg while maintaining a high resolution of 45 mN, which corresponds to 4.6 g. The proposed weight scale is suitable for time-lapse monitoring of body mass in seabird chicks. [Figure presented]

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Sampling-Moiré-Method Force Plate Array via Single-Step 3D-Printing

O Nomura, Y Nakahara, A Ogawa, H Takahashi

2025 23rd International Conference on Solid-State Sensors, Actuators and … 2025

Single-Step Fabrication of a Six-Axial Force Plate Using an FDM 3-D Printer

Yukitake Nakahara, Hidetoshi Takahashi

IEEE Sensors Journal 24 ( 7 ) 9691 - 9699 2024.04

ISSN 1530437X

Simple fabrication of customizable sensors is necessary for unique but important measurement objects. As force-sensing devices require multiple steps for fabrication, conventional techniques are not convenient for realizing tailor-made instruments. Recently, three-dimensionally (3-D) printed devices have become highly popular, especially for rapid prototyping. A 3-D printer can be used to fabricate complex structures in a single step and is ideal for fabricating custom sensors with advanced applications. In this study, we proposed a single-step fabrication method for a six-axial force plate using a fused deposition modeling dual-nozzle 3-D printer. The sensing elements were 3-D printed using electrically conductive polylactic acid filaments, and the entire force plate was fabricated in approximately one day. The device measured 230 mm, and the plate was square-shaped with dimensions of 100 mm. Calibration experiments were conducted, which confirmed that the fabricated force plate responded independently to the six-axial forces as designed. The resonant frequency was confirmed to be at least 45 Hz, and the force and moment resolutions were <5.9 mN and <4.2 mNm, respectively. Furthermore, the positional error was <3% in the Fz -direction. Therefore, the proposed fabrication method using a 3-D printer is useful for realizing a compact square-shaped sensing force plate, with a high degree of design freedom.

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Triaxial tactile sensor utilizing standing laser-induced graphene cantilevers on polyimide film

R Nakashima, H Takahashi

Sensors and Actuators A: Physical 365, 114919 (Sensors and Actuators A: Physical) 365 2024

ISSN 09244247

Microelectromechanical systems (MEMS) multiaxial tactile sensors have been developed in various fields to leverage their small size, high accuracy, and high sensitivity. Although various measurement principles have been proposed, most tactile sensors are fabricated using conventional and complicated Si processes. Conversely, laser-induced graphene (LIG) has recently attracted significant attention as a material for fabricating physical sensors due to its high sensitivity as a piezoresistor through simple laser processing. Therefore, the application of LIG to MEMS processes is expected to yield unprecedented MEMS sensor devices. In this paper, we propose a triaxial tactile sensor using standing LIG cantilevers embedded in an elastic body. The proposed sensing element was fabricated using ultraviolet (UV) laser irradiation to shape a polyimide film into cantilever structures and CO2 laser irradiation to form LIG strain gauges. Subsequently, the flat LIG cantilevers were stood up using thermal deformation. These multiple three-dimensional LIG cantilever elements enable multiaxial force measurements. The cantilever and elastic body portion of the sensor had dimensions of 3 × 3 × 0.2 mm and 12.5 × 12.5 × 3 mm, respectively. The fabricated sensor response was evaluated, and its capability to independently measure triaxial forces was verified. Therefore, the proposed simple and reproducible fabrication process is useful for realizing compact multiaxial tactile sensors.

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Triaxial force plate with prism imaging and sampling moiré method

O Nomura, H Takahashi

IEEE Sensors Journal 24 ( 7 ) 9671 - 9678 2024

ISSN 1530437X

Many studies have been conducted on the locomotion of terrestrial animals to evaluate ground reaction forces (GRFs) using a force plate. Conventional force plates typically utilize strain gauges, but there are challenges in developing small force plates. While force plates with noncontact type sensors have been developed, these are not suitable for multiaxial measurement. On the other hand, the sampling moiré (SM) method has garnered attention as a high-resolution in-plane measurement technique. This study proposes a force plate capable of triaxial force measurement with a single camera using the SM method. The proposed force plate comprises a plate, spring structure, 2-D grating, prism, and camera. Three directional displacements are measured from images that have two inclined grating images (GIs) before and after displacement by the SM method. In this study, we designed and fabricated a 25×25 mm force plate element with a resonant frequency of approximately 100 Hz. The fabricated force plate independently enabled three-axis measurements, with each axial force resolution < 1 mN, and the positional error for vertical forces remaining within ±3%. Therefore, the proposed sensor can be utilized for evaluating GRFs of small animals.

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Sleep-mask-type pulse wave and respiration rate sensor using a MEMS-based differential pressure sensing element

T Kato, TV Nguyen, H Takahashi

IEEE Sensors Journal 24 ( 13 ) 20402 - 20410 2024

ISSN 1530437X

Noninvasive sensors have been widely used to measure pulse and respiratory waves, which are the primary measurement targets in sleep monitoring. Conventional noninvasive biometric sensing devices, including smartwatches, require the use of multiple sensing elements and face challenges in the direct and simultaneous measurement of pulse and respiratory waves. Recently, pressure sensors with micro-electromechanical systems (MEMS)-based sensing elements have attracted attention for their small size, high sensitivity, and broad applicability. These sensors detect minute vibrations on the body surface with changes in pressure for biometric sensing. In this study, we propose a sleep-mask-type sensor for sleep monitoring that measures pulse and respiratory waves. A MEMS differential pressure (DP) sensor chip serves as a sensing element, which is placed between two chambers, one open to the atmosphere and the other with a rubber membrane. The proposed sensor detects minute vibrations of the dorsal surface of the nose, which can be attributed to pulse and respiratory waves based on DP changes in the chambers. This article presents the design, fabrication, and evaluation of the sensor with respect to capturing vibrations during sleep. The application of frequency filtering to the measured raw data confirmed that the pulse and respiratory waveforms could be directly and simultaneously measured, thereby rendering the proposed sensor suitable for sleep monitoring.

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Single-step fabrication of a 6-axial force plate using an FDM 3D printer

Y Nakahara, H Takahashi

IEEE Sensors Journal 2024

3D Printed Low Crosstalk 6-Axis Force Sensor Probe For Insects’ Jumping Force Measurement

Y Nakahara, H Takahashi

2024 IEEE 37th International Conference on Micro Electro Mechanical Systems … 837 - 840 2024

ISSN 10846999

This paper reports on a small 6-axis force sensor probe fabricated by a dual nozzle type fused deposition modeling (FDM) 3D printer. The proposed sensor probe consists of two coaxially connected PLA supporting structures in the out-of-plane and in-plane directions. Eight strain gauges are formed by electrically conductive PLA (EC-PLA) at the stress concentrations in each PLA structure in one dual-material print with automatic alignment. Thus, three-directional forces and three-directional moments can be measured with low crosstalk from the fractional resistance change of the eight strain gauges. The sensor probe can be produced and reproducibly and easily modified according to the measurement target. The fabricated sensor probe was calibrated and conducted to have 0.1 mN of force and 0.1 mNm of moment resolution with low crosstalk. Using the fabricated sensor probe, we demonstrated that the grasshopper's sheer vector jumping force was measured as 1 mN, assuming the sensor probe was a branch.

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Laser-Based Fabrication Process for Piezoresistive Cantilever Using Flash Laser Annealing

R Nakashima, T Kan, H Takahashi

2024 IEEE 37th International Conference on Micro Electro Mechanical Systems … 614 - 617 2024

ISSN 10846999

This paper reports a simple laser-based fabrication process for a piezoresistive cantilever involving flash laser annealing. The proposed process simultaneously realized a micro cantilever structure and an n-type piezoresistive sensing element by irradiating a dopant-coated Si wafer with a pulsed fiber laser. The fabricated sensors responded linearly to strain with a gauge factor over 10, a sufficiently useful value. The proposed process could serve as a rapid prototyping in MEMS processes involving semiconductor doping.

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Jumping dynamics of spherical shells driven by snap-through buckling

T Abe, S Shimizu, Y Nakahara, H Takahashi, G Ishigami, T Sano

APS March Meeting Abstracts 2024, B34. 014 2024

Experimental validation of a wave-height sensor based on a MEMS piezoresistive cantilever and a waterproof film

K Shimada, T Kishimoto, H Takahashi

Japanese Journal of Applied Physics 63 (12), 128003 63 ( 12 ) 2024

ISSN 00214922

This paper presents a barometric pressure-sensing wave-height sensor that employs a microelectromechanical system piezoresistive cantilever, an air chamber, and a micromesh waterproof film. The developed sensor has a height resolution of less than 5 mm in the 0.01-10 Hz frequency band and a high time resolution with 100 Hz sampling rate. We conducted wave height measurements at sea using the developed sensor and compared its performance with that of a commercial global positioning system buoy-type wave-height sensor.

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Dual-Measurement Pitot Tube Type Airflow and Waterflow Speed Sensor for Seabird Biologging

K Shimada, T Kishimoto, H Takahashi

2024 IEEE SENSORS, 1-4 2024

ISSN 19300395

This study reports on a Pitot tube type airflow and waterflow speed sensor for seabird biologging. Due to seabirds' remarkable ability to traverse the sea and sky, biologging method, in which sensors are attached to animals, has been used to measure their locomotion under natural conditions. To evaluate seabird locomotion, a sensor was required that could be attached to a seabird and directly measure relative air speed and water speed. Here, we propose a sensor that incorporates a Pitot tube structure and a polytetrafluoroethylene porous film with air permeability and waterproof properties. We achieved the ability to switch the measurement principle between air and water using the same sensor element, enabling the measurement of different pressure ranges. The sensor demonstrated adequate responsiveness to airflow ranging from 0-10 m/s and waterflow from 0-1.6 m/s in experiments.

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Designing a bathymetric sensor using absolute pressure sensors arranged on a regular polyhedron

R Ando, K Shimada, T Kishimoto, H Takahashi

IEEE Sensors Letters 8 ( 8 ) 2024

In oceanic environments, compact underwater drones must determine their positional information, including water depth, to move autonomously because wireless communication underwater is challenging. However, current bathymetric sensors often lack high accuracy, energy efficiency, and cost-effectiveness. We propose a spherical bathymetric sensor that uses multiple absolute pressure sensor elements, allowing precise water depth measurement without being affected by dynamic pressure caused by waterflow as well as offering low energy consumption and cost-effectiveness. This sensor has a spherical design with 12 absolute pressure sensor elements arranged in a regular dodecahedron, connected by a flexible Kiri-origami circuit. The water depth is determined by compensating for waterflow-induced error using sensor data and linear regression. We evaluated our method using both simulations and experiments. The sensor reduced waterflow-induced errors to within 7.5 mm in simulations and 5 mm in a water tunnel at a speed of 2.0 m/s. By comparison, conventional methods without error compensation showed errors exceeding 100 mm under the same conditions. The sensor was also validated to predict depth at different depths, resulting in a 6.5 mm error. These results suggest that our proposed sensor can effectively measure water depth for compact underwater drones.

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Cylindrical-Shaped Waterflow Vector Sensor Using Multiple Absolute-Pressure Sensors and Polynomial-Regression Models

K Shimada, T Kishimoto, H Tanaka, H Takahashi

IEEE Sensors Journal (Institute of Electrical and Electronics Engineers (IEEE)) 24 ( 23 ) 38822 - 38834 2024

ISSN 1530437X

With the growing interest in leveraging sensor technology for sustainable and efficient aquaculture, the measurement of ocean currents is considered a critical aspect of fish-cage environment monitoring. Conventional ocean-current sensors are typically large with high-energy consumption. Thus, they fall short of the specific demands for monitoring fish cages, which require the installation of multiple sensors in a small area. In this study, we developed a compact waterflow-vector sensor equipped with six absolute-pressure sensor elements. These elements measure the pressure on the surface of a cylinder-like housing. Through the application of fourth-degree polynomial regression, the pressure data are transformed into 2-D water-velocity and direction measurements. We fabricated a sensor based on a design informed by simulations and conducted circulating water-tunnel experiments using the fabricated sensor. Polynomial-regression models were constructed and validated from the experimental pressure output, and the models achieved an estimation accuracy of 0.21 m/s in velocity and 10° in direction within a 2.0 m/s range. Thus, our proposed sensor demonstrates the potential for monitoring sea currents in aquaculture.

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Airflow sensor using standing laser-induced graphene cantilevers

K Ohara, R Nakashima, H Takahashi

IEEE Sensors Journal 24 (7), 9585-9592 24 ( 7 ) 9585 - 9592 2024

ISSN 1530437X

Various animals in nature, particularly insects, possess sensory hairs that can detect minute fluid forces. Numerous airflow sensors, inspired by these insect sensory hairs, have been developed using silicon-based microelectro-mechanical systems (MEMS) technology. However, the intricate fabrication process and the challenge of integrating shape-controlled sensing elements on the same substrate have posed significant obstacles. On the other hand, laser-induced graphene (LIG) has emerged as a promising material for various physical sensors due to its high sensitivity as a piezoresistive material and its simplicity of production. Polyimide (PI), the most commonly used material for LIG formation, is thermoplastic, enabling the creation of 3-D shapes with ease. In this study, we propose a single-axis airflow sensor with upright LIG cantilevers. The process involves the use of an ultraviolet (UV) laser to cut a PI substrate into cantilever shapes and a CO2 laser to form LIG sensing elements. Subsequently, thermal deformation is employed to bend the cantilevers at right angles. The resulting sensor measures 25 × 25 mm at its base and stands at a height of 10.2 mm. Wind tunnel experiments validated the sensor s performance, showing a quadratic increase in response with wind velocity ranging from 2 to 12 m/s, consistent with theoretical expectations. Furthermore, the baseline shift observed with repeated wind application was significantly small. This approach holds great promise for the development of airflow sensors inspired by sensory hairs of insects.

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Liquid-immersion inclined-rotated exposure system for fabricating three-dimensional microstructures with large inclination angles

G Kagawa, H Takahashi

Journal of Micromechanics and Microengineering 34 (9), 095008 34 ( 9 ) 2024

ISSN 09601317

This study utilized liquid-immersion inclined-rotated ultraviolet lithography to fabricate three-dimensional (3D) microstructures. The maximum achievable inclination angles obtained through conventional inclined-rotated exposure (IRE) methods were limited by the significant refractive index differences in material. We proposed an IRE with liquid-immersion and adjustable mirrors, which enabled greater inclination angles with improved adjustability. Using liquid as a medium helped minimize the refractive index disparities between materials. We fabricated polydimethylsiloxane molds for micro suction cup (MSC) array sheets to evaluate the performance of the developed liquid-immersion IRE. The resulting MSC array sheets (10 mm2) with a suction cup diameter of 500 μm, achieved inclination angles up to 51°, approximately double those obtained with the conventional IRE method. In addition, the suction force of the fabricated MSC arrays were evaluated by pulling along the vertical, horizontal, and edge directions under wet conditions. The maximum measured suction force was 0.15 N, confirming the effectiveness of the proposed liquid-immersion IRE in fabricating 3D microstructures, as demonstrated by the fabricated MSC array sheets.

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Triaxial Force Plate with High Speed and Resolution Line Scan Camera for Sampling Moiré Method

Y Nakahara, O Nomura, H Takahashi

2024 IEEE SENSORS, 1-4 2024

ISSN 19300395

This study reports on a force sensing method to enable high-time resolution triaxial measurement by analyzing line-scan camera images through a prism using the sampling moire method (SM). It is well-known that conventional SM accurately measures the in-plane displacement of grid pattern images. Recently, it was reported that by combining SM with a prism, a force sensor capable of triaxial measurement can be realized. However, in the case of area scan cameras, high-time resolution is usually a trade-off with the number of pixels, which determines accuracy. Here, we combined a line scan camera with a high frame rate of 26 kHz and a wide view in the horizontal direction with an inclined pattern to achieve high independence three axes measurement.

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Transparent glass force plate with CrN strain gauges featuring a notch structure

R Oda, Y Okamoto, R Nakashima, Y Takei, H Takahashi

Journal of Micromechanics and Microengineering 35 (1), 015005 35 ( 1 ) 2024

ISSN 09601317

Microforce plate is a powerful tool as force sensors in the field of microelectromechanical systems (MEMS). These force plates can be used to quantitatively measure the minute insects’ ground reaction forces and microdroplets’ collision forces. During such measurements, there is often a demand specification for observing the interface between the object and the plate from the backside. However, transparent materials were not compatible with traditional MEMS force plate fabrication processes. Here, we propose a fabrication process for a transparent glass force plate by forming a notch structure on a glass substrate using chromium nitride (CrN) as a strain gauge. The force plate was designed as a 10 × 10 × 0.1 mm plate supported by beams on all four sides. The plate shape and groove formation were easily realized by applying a laser machining process to glass cutting. The force applied to the plate was measured using CrN strain gauges placed on a support beam. The fabricated force plate achieved a force resolution of less than 1 mN in the range of 100 mN. Additionally, the positional error across the entire plate was approximately ±10%. The proposed glass force plate is expected to be utilized in small-force measurements such as droplet collision observations, which require transparent plates for optical observation.

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Three-Dimensional Shape Optimized Seesaw-Type Force Sensor Fabricated with a Micro-Scale 3D Printer

S Sato, Y Nakahara, G Kagawa, M Asai, H Takahashi

2024 IEEE SENSORS, 1-4 2024

ISSN 19300395

This paper proposes a force sensor that utilizes three-dimensional (3D) shape optimization and 3D printing technology. Introduction of micro-scale 3D printing technology have simplified the fabrication processes of microdevices with complex geometries. At the same time, there have also been advancements in the optimization of 3D structures to achieve desirable performances. This study combined these two technologies to develop a force sensor for measuring the force of a soft actuator. The force sensor combines a typical probe geometry with a laser displacement sensor. Due to the millimeter-order scale of the sensor, the low rigidity of the resin material causes undesired torsional deformation. Through 3D shape optimization, a beam design with more than 70 % torsional displacement reduction was achieved without changes in spring constant. Furthermore, a beam printed by a micro-scale 3D printer showed elasticity. The relationship between the input force and laser displacement sensor output showed linear characteristics, indicating its suitability as a force sensor.

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Stretchable Pulse Wave Sensor with a Laser-Induced Graphene-Formed Kirigami Structure

S Oya, T Kato, G Kagawa, R Nakashima, H Takahashi

2024 IEEE SENSORS, 1-4 2024

ISSN 19300395

This paper reports on a stretchable laserinduced graphene (LIG) pulse-wave sensor based on a kirigami structure. The proposed sensor is fabricated by embedding a stretchable sensor element using the kirigami structure into an elastic material. The polyimide-based sensor element is formed by UV and CO2 laser irradiation, and the stretchable LIG strain gauges detect skin vibrations caused by pulse waves with high sensitivity. The proposed sensor could be stretched by up to 7.5 mm, and the sensitivity increased 27 times in the stretched state. Furthermore, the fabricated sensor was able to measure the pulse waves. Therefore, the proposed sensor shows potential as a stretchable wearable sensor for measuring pulse waves with high sensitivity.

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Snap and Jump: How Elastic Shells Pop Out

T Abe, I Hashiguchi, Y Nakahara, S Kobayashi, R Tarumi, H Takahashi, ...

arXiv preprint arXiv:2410.08525 2024

Sensitivity characteristics of a wave height sensor based on a MEMS piezoresistive cantilever and waterproof film

T Hirayama, H Takahashi

Japanese journal of applied physics 63 (2), 026505 63 ( 2 ) 2024

ISSN 00214922

This paper presents the frequency characteristics of a barometric pressure-sensing wave height sensor employing a MEMS piezoresistive cantilever and a micromesh waterproof film. The proposed sensor exhibited mechanical bandpass filter characteristics owing to air leakage around the cantilever and film. Consequently, high robustness can be achieved if the frequency is designed to match the wave range. We theoretically and experimentally verified that the frequency response is influenced by the film’s chamber volume and permeability constant. We demonstrated that the proposed frequency-response model helps design a waterproof wave height sensor using a cantilever-type differential pressure sensor.

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Sampling Moiré Method Force Plate Utilizing Smartphone Camera

O Nomura, A Ogawa, H Takahashi

IEEE Sensors Letters 8 ( 8 ) 2024

Ground reaction force (GRF) is a significant factor for evaluating foot biomechanics, and force plates (FPs) are commonly employed for assessment. Conventional FPs feature an integrated design of a supporting structure and sensor elements but face the challenges of high cost and limited customizability. Recently, high-resolution triaxial force measurements have been conducted using a prism and sampling moiré (SM) method within an optical experimental setup. Herein, we propose an FP that utilizes a commercial smartphone and the SM method. The proposed design simplifies the FP configuration, which comprises mechanical spring structures, a simple optical setup, smartphone, and smartwatch. We constructed a prototype FP of 200 mm × 400 mm capable of force resolution under 1 N. Camera images from the smartphone displayed two inclined grating images (GIs) via the prism, accurately reflecting vertical force applications. In the experiment, the developed FP measured the GRF in a manner similar to that of a commercial FP during human walking. The proposed method is practical for developing high-performance FPs.

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Pillar-Type Laser-Induced Graphene Airflow Sensor Assembled Via Kirigami/Origami Technique

K Ohara, R Nakashima, H Takahashi

2024 IEEE 37th International Conference on Micro Electro Mechanical Systems … 813 - 816 2024

ISSN 10846999

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Nest Box for Monitoring the Mass and Heart Rate Changes of a Growing Seabird Chick

Uematsu D., Kishimoto T., Harada K., Watanabe S., Sato K., Takahashi H.

IEEJ Transactions on Sensors and Micromachines 144 ( 1 ) 12 - 16 2024

ISSN 13418939

This study reports the development of a nest box that can be used to simultaneously measure changes in the mass and heart rate of a growing seabird chick. The nest box is equipped with two scales and a heart rate monitor. The zero-point drift is expected to be suppressed using two scales. The scale utilizes a noncontact displacement sensor with waterproofing and dustproofing. A silicone tube with one end closed and the other end connected to a pressure sensor is used as a heart monitor. The developed nest box allows noninvasive, sequential measurement of the mass and heart rate of a chick over several months.

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Nest Box for Monitoring the Mass and Heart Rate Changes of a Growing Seabird Chick

D Uematsu, T Kishimoto, K Harada, S Watanabe, K Sato, H Takahashi

ieej transactions on sensors and micromachines 144 (1), 12-16 2024

Enhancing force plate design through optimization of spring constant distribution

Y Kawasaki, A Ogawa, H Takahashi

Sensors and Actuators A: Physical 374, 115468 374 2024

ISSN 09244247

Force plates have been widely used in various scientific fields to measure ground reaction forces experienced by animals and humans. A force plate that incorporates mechanical springs and non-contact displacement sensors offers the advantages of facilely modifying its shape and performance. However, the design protocol was limited to adjusting the plate size and spring constants of the springs supporting the plate at the four corners. Herein, we propose an optimization method for determining the spring constant distribution of a force plate. The proposed design enables the use of simulations to optimize the mechanical properties of the force plate, such as resonant frequency and error due to position. The experimental results demonstrated that the resonant frequency of the fabricated force plate was 133 Hz and the error due to position was within ±5 %. These results confirm that the proposed force plate can be effectively adjusted through optimization.

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MEMS highly sensitive and large-area force plate for total ground reaction force measurement of running ant

H Takahashi, S Kohyama, T Takahata, I Shimoyama

Journal of Micromechanics and Microengineering 34 (4), 045006 34 ( 4 ) 2024

ISSN 09601317

Terrestrial insects exhibit agile manoeuvrability while running. However, the ground reaction force (GRF) in small insects remains poorly understood owing to its size and acting force. Here, we present a force plate for the measurement of total GRF during the running motion of ants with a force on the order of several tens of μN. The proposed force plate consists of a sufficiently large plate for several step cycles and four supporting cantilevers with highly sensitive piezoresistive elements. The plate and sensor chips were fabricated separately and combined during postprocessing. Two sizes of force plates were designed and fabricated for a large ant (Camponotus japonicas) and small ant (Messor aciculatus) with force resolution less than 1 μN. The developed force plates were calibrated by applying vertical forces at 32 points on the plate. Using the fabricated force plate, we measured the total GRF over several step cycles as the ant ran along the plate. Consequently, it was suggested that the ant ran with small vibrations in the direction of gravity.

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Measurement of Ground Reaction Forces in Sprint Running Using Insoles With 6-Axis Tactile Sensors.

H TAKAHASHI, KENI SHIMAZAKI

デサントスポーツ科学 (Web) 45, 12-21 2024

Needle-type pressure sensor with silicone oil and parylene membrane inside for minimally invasive measurement

Kishimoto T., Agetsuma M., Hoshino A., Takahashi H.

Electronics and Communications in Japan 106 ( 3 ) 2023.09

ISSN 19429533

This paper addresses a pressure sensor for body pressure measurement. Many pressure sensors have been developed for disease treatment in the medical field. However, these sensors require inserting electronic components and other sensor elements via surgical operations, so the measurement physically burdens patients. Hence, we proposed a needle-type pressure sensor using MEMS (Micro Electro Mechanical Systems) cantilever. The sensor has a needle part with a thin membrane on the tip and is filled with incompressible fluid inside. The fractional resistance of the built-in piezoresistive cantilever varies according to the pressure change applied to the needle tip. We can measure body fluid pressure with minimal surgery by inserting a simple needle into the target organ. Because the fabricated sensor responded to pseudo-body pressure changes, it was suggested that the fabricated needle-type pressure sensor could detect pressure inside the body.

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Temperature Dependence of the Beating Frequency of hiPSC-CMs Using a MEMS Force Sensor

R Ikegami, T Tsukagoshi, K Matsudaira, KH Shoji, H Takahashi, ...

Sensors 23 (7), 3370 (Sensors) 23 ( 7 ) 2023.04

ISSN 14248220

It is expected that human iPS cell-derived cardiomyocytes (hiPSC-CMs) can be used to treat serious heart diseases. However, the properties and functions of human adult cardiomyocytes and hiPSC-CMs, including cell maturation, differ. In this study, we focused on the temperature dependence of hiPSC-CMs by integrating the temperature regulation system into our sensor platform, which can directly and quantitatively measure their mechanical motion. We measured the beating frequency of hiPSC-CMs at different environmental temperatures and found that the beating frequency increased as the temperature increased. Although the rate at which the beating frequency increased with temperature varied, the temperature at which the beating stopped was relatively stable at approximately 20 °C. The stopping of beating at this temperature was stable, even in immature hiPSC-CMs, and was considered to be a primitive property of cardiomyocytes.

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Open planar acoustic notch filter using a film-integrated Helmholtz resonator array

F Mizukoshi, H Takahashi

Japanese Journal of Applied Physics 62 (3), 034002 (Japanese Journal of Applied Physics) 62 ( 3 ) 2023.03

ISSN 0021-4922

Acoustic filters are used to transmit or attenuate noise in a specific frequency band. However, previous acoustic filters consisting of rigid structures generally required a large housing of a size equivalent to the wavelength, limiting their downsizing. This study presents an open planar acoustic notch filter using a film-integrated Helmholtz resonator (HR) array. A film divides the HR chamber and resonates with the HR. The film-integrated HR array filter achieved smaller housing dimensions than a no-film HR array filter with the same notch frequency. The transmittance of the film-integrated HR array was theoretically calculated using the transfer matrix method. The calculated spectra were very similar to the simulation results. The notch frequency of the film-integrated HR array filter was 4.04, 0.74 kHz lower than a no-film HR array filter. The design and analysis of the acoustic filter presented should motivate further development of advanced acoustic filters.

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Sensitivity characteristics of a waterproof airflow sensor based on a MEMS piezoresistive cantilever and nanohole array

T Hirayama, Y Kazoe, H Takahashi

Japanese Journal of Applied Physics 62 (2), 026503 (Japanese Journal of Applied Physics) 62 ( 2 ) 2023.02

ISSN 0021-4922

This paper presents the sensitivity characteristics of a microelectromechanical systems (MEMS) piezoresistive cantilever and nanohole array used in a waterproof airflow sensor. Previously, a Pitot tube-type waterproof airflow sensor was developed for seabird biologging. Built-in MEMS piezoresistive cantilevers are used as the differential pressure sensing elements. The waterproof function is achieved using nanohole arrays via Laplace pressure. However, the mechanism underlying sensitivity reduction when nanohole arrays are attached is unclear. Here, we experimentally and theoretically verified that the specific constant, which determines the airflow rate through the cantilever and nanohole array, affects sensitivity reduction. An airflow sensor with a small sensitivity reduction was achieved based on the calculated results using appropriate cantilever and nanohole arrays. We demonstrated that the proposed method for estimating sensitivity reduction is useful for designing waterproof airflow sensors using cantilever-type differential pressure sensor elements.

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Spiral Spring-Supported Force Plate with an External Eddy Current Displacement Sensor

Y Kawasaki, H Takahashi

Actuators 12 (1), 16 (Actuators) 12 ( 1 ) 2023.01

This study proposes a force plate with a planar spring and an eddy current displacement sensor to measure the ground reaction force (GRF) of a small insect and reveal its motion characteristics. The proposed force plate comprises a circular aluminum plate, four aluminum springs symmetrically connected to the plate, and an eddy current displacement sensor under the plate. The diameter and thickness of the fabricated plate were 8 and 0.1 mm, respectively. The spring width was 0.4 mm. When a force is applied to the plate, the plate moves vertically downward. Then, an eddy current displacement sensor detects the plate displacement without contact. The applied force can be measured using Hooke’s law. The proposed force plate has the advantages of ease of fabrication and cost-effectiveness. The central displacement variation and resonant frequency of the designed springs were evaluated by simulation. Then, we calibrated the fabricated force plate to obtain the sensitivity variation and resonant frequency. The experimental results suggest that the proposed force plate can effectively measure the GRF of a small insect.

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Highly Sensitive Low-Frequency-Detectable Acoustic Sensor Using a Piezoresistive Cantilever for Health Monitoring Applications

Y Okamoto, TV Nguyen, H Takahashi, Y Takei, H Okada, M Ichiki

Scientific reports 13 (1), 6503 (Scientific Reports) 13 ( 1 ) 2023

This study investigates a cantilever-based pressure sensor that can achieve a resolution of approximately 0.2 mPa, over the frequency range of 0.1–250 Hz. A piezoresistive cantilever with ultra-high acoustic compliance is used as the sensing element in the proposed pressure sensor. We achieved a cantilever with a sensitivity of approximately 40 times higher than that of the previous cantilever device by realizing an ultrathin (340 nm thick) structure with large pads and narrow hinges. Based on the measurement results, the proposed pressure sensor can measure acoustic signals with frequencies as low as 0.1 Hz. The proposed pressure sensor can be used to measure low-frequency pressure and sound, which is crucial for various applications, including photoacoustic-based gas/chemical sensing and monitoring of physiological parameters and natural disasters. We demonstrate the measurement of heart sounds with a high SNR of 58 dB. We believe the proposed microphone will be used in various applications, such as wearable health monitoring, monitoring of natural disasters, and realization of high-resolution photoacoustic-based gas sensors. We successfully measured the first (S1) and second (S2) cardiac sounds with frequencies of 7–100 Hz and 20–45 Hz, respectively.

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Thin Glass Micro Force Plate Supported by Planar Spiral Springs for Measuring Minute Forces

T Kiriyama, K Shimazaki, R Nakashima, H Takahashi

Micromachines 14 (5), 1056 (Micromachines) 14 ( 5 ) 2023

Microforce plates are indispensable tools for quantitatively evaluating the behavior of small objects such as tiny insects or microdroplets. The two main measurement principles for microforce plates are: the formation of strain gauges on the beam that supports the plate and the measurement of the deformation of the plate using an external displacement meter. The latter method is characterized by its ease of fabrication and durability as strain concentration is not required. To enhance the sensitivity of the latter type of force plates with a planar structure, thinner plates are generally desired. However, brittle material force plates that are both thin and large and can be fabricated easily have not yet been developed. In this study, a force plate consisting of a thin glass plate with a planar spiral spring structure and a laser displacement meter placed under the plate center is proposed. The plate deforms downward when a force is exerted vertically on its surface, resulting in the determination of the applied force using Hooke’s law. The force plate structure is easily fabricated by laser processing combined with the microelectromechanical system (MEMS) process. The fabricated force plate has a radius and thickness of 10 mm and 25 µm, respectively, with four supporting spiral beams of sub-millimeter width. A fabricated force plate featuring a sub-N/m spring constant achieves a resolution of approximately 0.01 µN.

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Neural network-based airflow vector sensor using multiple MEMS differential pressure sensors

K Haneda, K Matsudaira, H Takahashi

IEEE Access 11 40978 - 40987 2023

As airflow information is significant in various fields, several airflow measurement devices have been developed. Differential pressure (DP)-type sensors, including pitot tubes, are extensively used because they can directly measure dynamic pressure due to airflow. However, this method has a disadvantage in that it is difficult to measure some wind directions because of the non-monotonic pressure distribution around the device. This study proposes a compact sphere airflow vector sensor using a neural network model that compensates for nonmonotonicity. It consists of three built-in microelectromechanical system (MEMS)-based DP sensor elements that simultaneously measure the DPs around the spherical sensor housing. The measured DPs are converted into 2D wind speed and direction using a neural network. The network model was trained using the simulated output of each sensor, and it was confirmed that the proposed design guideline contributed to achieving high accuracy. An airflow sensor was fabricated on the basis of the designed model. A network model was trained using the sensor responses in a wind tunnel experiment. The wind speed and direction accuracies obtained by the neural network model for 2-10 m/s and 0°-359° were 0.24 m/s and 3.62°, respectively. Finally, we demonstrated a drone flight test by attaching the calibrated sensor to a toy drone. This study is expected to contribute to realizing highly accurate low airflow measurement devices.

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Multi-Mems Differential Pressure Sensor Elements-Based Airflow Sensor with Neural Network Model

K Haneda, K Matsudaira, H Takahashi

2023 IEEE 36th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2023-January 499 - 502 2023

ISSN 1084-6999

This paper reports a compact spherical airflow sensor using multi-MEMS differential pressure (DP) sensor elements. Three built-in MEMS sensors simultaneously measure the DP around the spherical housing structure so that the measured DPs are converted into 2D wind direction and speed. The sensor outputs are converted into wind direction and speed by neural network. We attached the calibrated sensor to a toy drone as a demonstration. Then, it was confirmed that the output corresponding to wind direction and speed was measured when a crosswind was applied during flight.

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Liquid-Immersion Inclined-Rotated UV Lithography for Micro Suction Cup Array

G Kagawa, H Takahashi

ISSN 1084-6999

This paper reports liquid-immersion inclined/rotated UV lithography for fabricating micro suction cups. Microstructures such as micro suction cups have been applied in various applications. However, the conventional fabrication method had limitations in suction force due to the insufficient inclination angle. We proposed liquid-immersion to inclined/rotated exposure (IRE), enabling greater microstructure inclination angles. IRE equipment was developed to fabricate PDMS micro suction cup arrays. The experimental inclination angle reached 51°, nearly doubling the conventional IRE method.

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Lig-Based Triaxial Tactile Sensor Utilizing Rotational Erection System

R Nakashima, N Nakamura, TG Sano, E Iwase, H Takahashi

ISSN 1084-6999

This paper reports a laser-induced graphene (LIG)based triaxial tactile sensor utilizing rotational erection system (RES). The proposed process realizes a sensing element with a piezoresistive layer by irradiating a polyimide (PI) film with two types of lasers only once each. Furthermore, the sensing element formed with origami/kirigami method maintains a three-dimensional structure by applying a single external force. The prototype triaxial tactile sensor fabricated by the proposed fabrication process responded independently to normal and shear forces.

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Highly Sensitive Wave Height Sensor with MEMS Piezoresistive Cantilever and Waterproof Membrane

T Hirayama, H Takahashi

2023 IEEE 36th International Conference on Micro Electro Mechanical Systems … 760 - 762 2023

ISSN 1084-6999

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Triaxial tactile sensor using RES structure and standing LIG cantilevers

R NAKASHIMA, T SANO, N NAKAMURA, E IWASE, H TAKAHASHI

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 40, 3-4 2023

Triaxial piezoresistive force sensor probe with high sensitivity and stiffness using 3D notch structure

H Takahashi, Y Takei, K Noda, K Matsumoto, I Shimoyama

Journal of Micromechanics and Microengineering 33 (12), 125005 (Journal of Micromechanics and Microengineering) 33 ( 12 ) 2023

ISSN 09601317

This paper proposes a microelectromechanical system triaxial piezoresistive force sensor probe with high sensitivity and stiffness. The sensor probe is composed of a cantilever and four supporting beams. Two of the four beams had horizontal notch parts at the root, and sidewall-doped piezoresistors were utilised to detect the in-plane deformation. There was a vertical notch at the root of the remaining two beams and a surface-doping piezoresistor in one beam to detect the out-of-plane deformation. Thus, the proposed sensor probe measures the three directional forces applied to the cantilever tip with high sensitivity and stiffness owing to the corresponding piezoresistive notch structures. We demonstrate a fabrication process that forms the notch structure and the surface and sidewall doping methods. Our fabricated device was confirmed capable of measuring triaxial forces with a force resolution at the sub-micro-Newton level.

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Single step fabrication of a triaxial force plate using 3D printer

Y NAKAHARA, H TAKAHASHI

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 40, 5-31 2023

Simple hearing test utilizing a soundproofing headphone with acoustic filters

F Mizukoshi, N Oishi, H Takahashi

Biomedical Engineering Advances 6, 100102 2023

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Airflow Sensor Using MEMS Differential Pressure Sensors and Neural Network

KENEI MATSUDAIRA, K HANEDA, T KISHIMOTO, H TAKAHASHI

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 40, 5-30 2023

MEMS 6-axis force sensor chip for spike pins in athletic sports shoes

H Takahashi, H Ishido, A Nakai, T Takahata, K Matsumoto, I Shimoyama

Sensors and Actuators A: Physical 363, 114702 363 2023

ISSN 09244247

This study reports a microelectromechanical system (MEMS) sensor for evaluating the force acting on the spike pins of athletic sports shoes. The ground reaction force (GRF) of the human sole is a crucial factor in understanding running mechanics. In short-distance sprints, running is achieved by biting the ground using shoe spikes. However, it is difficult to evaluate the forces acting on such spike pins because of their small size. In this study, a MEMS sensor chip that could measure the 6-axis forces was embedded in an actual spike-pin-shaped structure, and the fabricated spike pin was attached to athletic shoes. By utilizing four pairs of surface- and sidewall-doped beams as sensing elements, the 6-axis force acting on the pin can be measured regardless of the force distribution when the pin bites into the track. We demonstrated that the force distribution could be measured using three sensors developed during running. The vertical force on each pin exceeded 100 N. Furthermore, it was observed that higher propulsive forces were exerted on all the spike pins in the first step compared to the second step or later steps. Therefore, the proposed method can be used to evaluate running mechanics using spike pins in athletic sports shoes.

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Two-dimensional waterflow sensor using multiple absolute pressure sensors

K Shimada, T Kishimoto, H Tanaka, H Takahashi

2023 IEEE SENSORS, 1-4 2023

ISSN 19300395

This study reports a two-dimensional (2D) waterflow sensor for marine aquaculture. In recent years, environmental monitoring has been widely developed in marine aquaculture. Among these monitoring, ocean currents are one of the important factors in capturing the inflow of hypoxic water into fish cages. However, there were no low-power, simple waterflow sensors that could be adapted to fish cages. Here we propose a waterflow sensor using with a cylindrical housing and an array of six absolute pressure sensor elements to measure 2D waterflow velocity around a fish cage. 2D waterflow velocity is calculated via a polynomial regression model of the responses of six pressure sensors and sensor tilt angle. By constructing the model for each tilt angle, the developed sensor responded with sufficient sensitivity to waterflow velocities from 0.4 to 2.0 m/s.

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Pressure sensor with a corrugated structure utilizing LIG sensing element

R Oda, R Nakashima, H Takahashi

2023 22nd International Conference on Solid-State Sensors, Actuators and … 1601 - 1603 2023

This paper reports on a pressure sensor with a corrugated structure utilizing a laser-induced graphene (LIG) strain gauge. A concentrically expanding corrugated structure is formed on a polyimide (PI) film by a UV laser. A LIG layer, which function as a piezoresistor, is directly formed by a CO2 laser to the outermost circumference of the corrugated structure. Using two different-types laser processing, a highly sensitive pressure sensor is easily realized. Here we theoretically and experimentally show the proposed method usefulness by evaluating the sensor response.

Pitot-Type Waterflow Sensor Logger for Relative Waterflow Velocity Measurement of a Sea Turtle

T Kishimoto, R Saito, H Tanaka, M Naruoka, K Kuroda, K Sato, ...

2023 22nd International Conference on Solid-State Sensors, Actuators and … 698 - 701 2023

This study presents a waterflow sensor logger for sea turtles. Many sensors have been attached to wild animals via the biologging method for animal ecological analysis. However, it is not easy to measure the relative waterflow velocity of marine animals with a conventional sensor due to marine debris and algae. Furthermore, there are limited examples of measurements for sea turtles. Here, we proposed a Pitot-type waterflow sensor logger. The sensor logger achieves both resistance to algae and marine debris and pressure resistance because of the Pitot-type waterflow sensor structure. Attaching the sensor logger to a sea turtle's carapace will make long-term velocity measurement possible. The fabricated sensor logger responded stably to waterflow and measured actual sea turtle's swimming as waterflow velocity.

Pitot Tube Type Compact Waterproof Airflow Sensor for Seabird Biologging

T Hirayama, T Kishimoto, H Takahashi

2023 IEEE SENSORS, 1-4 2023

ISSN 19300395

In this study, a waterproof airflow sensor is proposed for seabird biologging. Biologging, in which a sensor is directly attached to an animal to record its behavior, has attracted much attention to assess the animal's locomotion performance. Among them, it has been focused to evaluate the flight performance of seabirds. An airflow sensor becomes a powerful tool to measure the self-induced flight velocity of a seabird, however, the sensor is also required to have water pressure resistance. Here we propose a Pitot tube type compact waterproof airflow sensor with micromesh filters for seabird biologging. The Pitot tube structure with built-in the differential pressure sensor element realized a compact and robust sensor performance. The micro-mesh filter was attached to the air inlets to achieve high water pressure resistance. The developed sensor responded with high sensitivity to pressures up to 100 Pa and airflow up to 10 m/s without any loss of sensitivity caused by the filter.

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One Step Fabrication of Triaxial Force Plate Using a FDM 3D Printer

Y Nakahara, H Takahashi

2023 22nd International Conference on Solid-State Sensors, Actuators and … 1759 - 1761 2023

This paper reports a triaxial force plate which is entirely fabricated in a single step with a fused deposition modeling (FDM) 3D printer. The force plate consists of strain gauges and body structure. The strain gauges measure the force by fractional resistance changes, which is printed with electrical conductive poly-lactic acid (EC PLA). 3D printers specialize in forming three-dimensional parts, it can create multiple strain gauges of complex shapes simultaneously without any specific jigs such as photo masks. The body structure has a plate and pillars, which strain uniquely in response to the loaded triaxial forces. The prototype force plate fabricated by the proposed fabrication method was confirmed to respond independently to vertical and horizontal forces.

Nest Box for Monitoring the Mass and Heart Rate Changes of a Growing Seabird Chick

Uematsu D., Kishimoto T., Harada K., Watanabe S., Sato K., Takahashi H.

2023 22nd International Conference on Solid-State Sensors, Actuators and Microsystems, Transducers 2023 1591 - 1594 2023

This paper reports the development of a nest box in which changes in the mass and heart rate of a growing seabird chick can be simultaneously measured. The nest box is equipped with two scales and a heart rate monitor. By using two scales, zero-point drift is expected to be suppressed. A non-contact displacement sensor that has environmental resistance is used as the sensor element for the scales. As a heart monitor, a tube with one end closed and the other end connected to a pressure sensor is used. The developed nest box will allow non-invasive, sequential measurement of the mass and heart rate of chicks over a long time.

Needle‐type pressure sensor with silicone oil and parylene membrane inside for minimally invasive measurement

T Kishimoto, M Agetsuma, A Hoshino, H Takahashi

Electronics and Communications in Japan 106 (3), e12420 2023

Needle-Type Pressure Sensor with Silicone Oil and Parylene Membrane inside for Minimally Invasive Measurement

Kishimoto T., Agetsuma M., Hoshino A., Takahashi H.

IEEJ Transactions on Sensors and Micromachines 143 ( 7 ) 148 - 155 2023

ISSN 13418939

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MEMS Differential Pressure Sensor with Dynamic Pressure Canceler for Precision Altitude Estimation

S Yasunaga, H Takahashi, T Takahata, I Shimoyama

Micromachines 14 (10), 1941 14 ( 10 ) 2023

Atmospheric pressure measurements based on microelectromechanical systems (MEMSs) can extend accessibility to altitude information. A differential pressure sensor using a thin cantilever and an air chamber is a promising sensing element for sub-centimeter resolution. However, its vulnerability to wind and the lack of height estimation algorithms for real-time operation are issues that remain to be solved. We propose a sensor “cap” that cancels the wind effect and noise by utilizing the airflow around a sphere. A set of holes on the spherical cap transmits only the atmospheric pressure to the sensor. In addition, we have developed a height estimation method based on a discrete transfer function model. As a result, both dynamic pressure and noise are suppressed, and height is estimated under a 5 m/s wind, reconstructing the trajectory with an estimation error of 2.8 cm. The developed sensing system enhances height information in outdoor applications such as unmanned aerial vehicles and wave height measurements.

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斜立した LIG カンチレバーを利用した風速センサ

S OHARA, R NAKAJIMA, H TAKAHASHI

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 40, 2-19 2023

Relative Waterflow Velocity Logger for a Sea Turtle Using Pitot-type Waterflow Velocity Sensor

T KISHIMOTO, R SAITO, H TANAKA, M NARUOKA, K KURODA, K SATO, ...

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 40, 3-3 2023

Liquid-immersion inclined UV lithography using cube prism and mirrors

G Kagawa, T Sugimoto, H Takahashi

Applied Physics Express 15 (11), 116501 (Applied Physics Express) 15 ( 11 ) 2022.11

ISSN 1882-0778

This paper reports on the inclined UV lithography based on liquid immersion. The proposed method implements liquid immersion, allowing structures to be formed with a large inclination angle. The equipment comprises two adjustable mirrors and a cubic glass with a pure water chamber. UV light rays are reflected and passed through the mirrors and chamber, irradiating the target at an inclined angle. We developed the necessary equipment and fabricated the 3D microstructures. The results revealed that the inclination angle reached up to 49°, indicating exposures beyond the limits of conventional inclined UV lithography.

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A Polyimide Film-Based Simple Force Plate for Measuring the Body Mass of Tiny Insects

K Shimazaki, T Sugimoto, H Toda, H Takahashi

Sensors 22 (21), 8352 (Sensors) 22 ( 21 ) 2022.11

ISSN 14248220

Insects exhibit excellent maneuvers such as running and flying despite their small bodies; therefore, their locomotion mechanism is expected to provide a design guideline for micromachines. Numerical simulations have been performed to elucidate this mechanism, whereby it is important to develop a model that is physically identical to the target insect’s parts to reproduce kinematic dynamics. In particular, in flight, the shape and mass of wings, which flap at high frequencies, are significant parameters. However, small insects such as fruit flies have small, thin, and light wings; thus, their mass cannot be easily measured. In this study, we proposed a high-resolution and simple force plate to measure the mass of each part of a tiny insect. The device consists of a circular plate supported by flat spiral springs made of polyimide film, and a laser displacement meter that detects the displacement of the center of the plate. The simple plate fabrication process requires only a couple of minutes. A fabricated force plate with a sub-N/m spring constant achieved a resolution of less than 2 µg. As a demonstration, the wing mass of the fruit flies was measured. The experimental results suggest that the wings accounted for approximately 0.4% of the body mass.

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Frequency-specific highly sensitive acoustic sensor using a piezoresistive cantilever element and parallel Helmholtz resonators

R Wada, H Takahashi

Sensors and Actuators A: Physical 345, 113808 (Sensors and Actuators A: Physical) 345 2022.10

ISSN 0924-4247

Acoustic sensors for specific-frequency detection are used in various applications, and their sensitivity improvement has been attracting significant attention. Mechanical acoustic resonator technology is an effective method because of its simple structure and low power consumption. A Helmholtz resonator (HR) is a typical mechanical resonator; however, previous HRs for an acoustic sensor were attached to the rear of the sensing element, which was unsuitable for a differential pressure (DP) sensor that blocks the pressure wave propagating through the sensor chip. This paper proposes a micro-electro-mechanical system (MEMS)-based acoustic sensor, enhanced by a front-mounted parallel HR array, which is suitable for a DP sensor-type element. A piezoresistive cantilever-type DP sensor was used as the sensing element because of its high sensitivity to acoustic waves in its mechanical resonant frequency (RF) range. Its sensitivity was enhanced by attaching an HR array to the DP sensor, like a cap. We designed and fabricated a piezoresistive cantilever with dimensions 80 × 80 × 0.2 µm and an RF of 4.5 kHz, and four HR arrays with an RF close to that of the cantilever. The sensor responses to acoustic waves with and without the HRs were evaluated. The developed sensor with the HR realized three times higher sensitivity than those without the HR at the RF. The obtained acoustic pressure resolution was approximately 4 mPa.

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Measurement method of a microspring-supported force plate with an external laser displacement meter

T Sugimoto, Y Kawasaki, H Toda, H Takahashi

Measurement Science and Technology 33 (10), 105118 ({IOP} Publishing) 33 ( 10 ) 2022.10

ISSN 0957-0233

Ground reaction force (GRF) is a significant factor for the evaluation of animal locomotion. Recently, micro force plates have been implemented as a GRF measurement method for tiny insects. Previous micro force plates were highly sensitive, but fragile and laborious to fabricate, because of the use of strain-sensing elements. Here, we applied high-resolution 3D printing and a noncontact displacement meter to a micro force plate for a fruit fly. 3D printing is suitable for easier, reproducible, and complex three-dimensional fabrication so that a force plate structure, which consists of a plate and four supporting 3D microsprings, is developed as an integrated unit. By detecting the displacement of the plate centre externally, when a fruit fly lands on the plate surface, the vertical GRF of the whole device is calculated via the spring constant. The force plate is sufficiently tough due to the supporting 3D microsprings. The spring constant of the microspring is designed to be approximately 5.98 N m−1, which enables a high-resolution external laser displacement meter to realize a force resolution of less than 1/50 of the body weight of a fruit fly. Providing that the four springs have the same spring constant and the displacement meter aligns at the plate centre, in principle, there is no positional error when converting from displacement to force. However, fabrication error does lead to spring constant differences. Here, we theoretically and experimentally determined the measurement point of the displacement sensor where the positional error caused by the difference in the spring constant of the four microsprings is compensated for. It was confirmed in the experiment that the calibration process improved the position error to be within ±1.5%. Finally, we demonstrated the GRF measurement of a fruit fly. The average GRF was 6.5 μN, which was equal to the weight of a fruit fly. Our proposed device can help evaluate the biomechanics of tiny insects.

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MEMS-Based Micro Sensors for Measuring the Tiny Forces Acting on Insects

H Takahashi

Sensors 22 (20), 8018 (Sensors) 22 ( 20 ) 2022.10

ISSN 14248220

Small insects perform agile locomotion, such as running, jumping, and flying. Recently, many robots, inspired by such insect performance, have been developed and are expected to be smaller and more maneuverable than conventional robots. For the development of insect-inspired robots, understanding the mechanical dynamics of the target insect is important. However, evaluating the dynamics via conventional commercialized force sensors is difficult because the exerted force and insect itself are tiny in strength and size. Here, we review force sensor devices, especially fabricated for measuring the tiny forces acting on insects during locomotion. As the force sensor, micro-force plates for measuring the ground reaction force and micro-force probes for measuring the flying force have mainly been developed. In addition, many such sensors have been fabricated via a microelectromechanical system (MEMS) process, due to the process precision and high sensitivity. In this review, we focus on the sensing principle, design guide, fabrication process, and measurement method of each sensor, as well as the technical challenges in each method. Finally, the common process flow of the development of specialized MEMS sensors is briefly discussed.

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Frequency Characteristics of Pulse Wave Sensor Using MEMS Piezoresistive Cantilever Element

T Nabeshima, TV Nguyen, H Takahashi

Micromachines 13 (5), 645 ({MDPI} {AG}) 13 ( 5 ) 645 - 645 2022.05

Wearable sensor devices with minimal discomfort to the wearer have been widely developed to realize continuous measurements of vital signs (body temperature, blood pressure, respiration rate, and pulse wave) in many applications across various fields, such as healthcare and sports. Among them, microelectromechanical systems (MEMS)-based differential pressure sensors have garnered attention as a tool for measuring pulse waves with weak skin tightening. Using a MEMS-based piezoresistive cantilever with an air chamber as the pressure change sensor enables highly sensitive pulse-wave measurements to be achieved. Furthermore, the initial static pressure when attaching the sensor to the skin is physically excluded because of air leakage around the cantilever, which serves as a high-pass filter. However, if the frequency characteristics of this mechanical high-pass filter are not appropriately designed, then the essential information of the pulse-wave measurement may not be reflected. In this study, the frequency characteristics of a sensor structure is derived theoretically based on the air leakage rate and chamber size. Subsequently, a pulse wave sensor with a MEMS piezoresistive cantilever element, two air chambers, and a skin-contacted membrane is designed and fabricated. The developed sensor is 30 mm in diameter and 8 mm in thickness and realizes high-pass filter characteristics of 0.7 Hz. Finally, pulse wave measurement at the neck of a participant is demonstrated using the developed sensor. It is confirmed that the measured pulse wave contains signals in the designed frequency band.

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Compact Sphere-Shaped Airflow Vector Sensor Based on MEMS Differential Pressure Sensors

K Haneda, K Matsudaira, R Noda, T Nakata, S Suzuki, H Liu, H Takahashi

Sensors 22 (3), 1087 (MDPI AG) 22 ( 3 ) 1087 - 1087 2022.02

ISSN 14248220

This paper presents an airflow vector sensor for drones. Drones are expected to play a role in various industrial fields. However, the further improvement of flight stability is a significant issue. In particular, compact drones are more affected by wind during flight. Thus, it is desirable to detect air current directly by an airflow sensor and feedback to the control. In the case of a drone in flight, the sensor should detect wind velocity and direction, particularly in the horizontal direction, for a sudden crosswind. In addition, the sensor must also be small, light, and highly sensitive. Here, we propose a compact spherical airflow sensor for drones. Three highly sensitive microelectromechanical system (MEMS) differential pressure (DP) sensor chips were built in the spherical housing as the sensor elements. The 2D wind direction and velocity can be measured from these sensor elements. The fabricated airflow sensor was attached to a small toy drone. It was demonstrated that the sensor provided an output corresponding to the wind velocity and direction when horizontal wind was applied via a fan while the drone was flying. The experimental results demonstrate that the proposed sensor will be helpful for directly measuring the air current for a drone in flight.

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3D Printed Micro Force Plate for Measuring the Ground Reaction Force of a Fruit Fly

T Sugimoto, H Toda, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 703 - 705 2022

ISSN 1084-6999

This paper reports on a micro force plate for a fruit fly, which is fabricated by a high-resolution 3D printer. The conventional force sensors for tiny insects were highly sensitive but fragile and took much time to be fabricated. The proposed force plate achieves both high sensitivity and toughness via completely 3D supporting micro-springs and an external laser displacement meter. The plate structure integrated with the micro-springs is easily and reproducibly printed in a single process. When a fruit fly lands on a plate surface, the ground reaction force (GRF) is measured with force resolution less than 1/50 of the body weight from the plate displacement via the laser displacement meter. Our proposed device is helpful to evaluate the biomechanics of tiny insects.

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Tunable planar acoustic notch filter utilizing pneumatic deforming Helmholtz resonator array

F Mizukoshi, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 849 - 851 2022

ISSN 1084-6999

This paper reports a tunable acoustic notch filter utilizing a Helmholtz resonator (HR) array. Passive acoustic filters based on mechanical resonators have the advantages of no power supply requirement; however, the filtering frequency is not adjustable compared to active noise control. The proposed device consists of three-layered parts: cavities, a membrane, and microchannels. The cavities work as HR chambers, which determine the resonant frequency. Due to the HR effect, the acoustic wave is effectively insulated at the frequency. The HR chamber volume can be changed by deforming the membrane with air pressure through the microchannels. Thus, it enables adjustment of the resonant frequency, realizing a tunable acoustic notch filter. The prototype device realized the frequency tuning approximately from 4 to 5 kHz with 10 dB filtering. Thus, it can handle a wide range of high-frequency noises that humans tend to find uncomfortable.

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Sensitivity Enhancement of An Acoustic Sensor via Parallel Helmholtz Resonators

R Wada, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 833 - 836 2022

ISSN 1084-6999

This paper reports an acoustic sensor using a Helmholtz resonator (HR) array and a MEMS differential pressure (DP) sensor element. A piezoresistive cantilever type DP sensor is highly sensitive to acoustic waves around its mechanical resonant frequency (RF). By attaching a HR array of which RF is equal to the cantilever in front of the DP sensor like a cap, the sensitivity is enhanced at the RF. The developed sensor with the HR responded with 3 times higher sensitivity than without the HR, and realized a resolution of approximately 2 mPa without an electrical lock-in filter.

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Needle Type Pressure Sensor with Parylene Membrane and Silicone Oil Inside

T Kishimoto, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 668 - 671 2022

ISSN 1084-6999

This study presents a pressure sensor that can measure the pressure inside the human body. In the medical field, many pressure sensors have been developed for therapeutic applications. However, these pressure sensors require the whole sensor body to be put into the inside of the patient via surgical operations so that the measurement physically burdens patients. Here, we propose a needle-type pressure sensor with a built-in piezoresistive cantilever. The proposed sensor has a needle part with a thin membrane on the tip and is filled with incompressible liquid inside. By ply inserting a needle part into a target, we can measure the body fluid pressure with minimal invasiveness. The resistance of the built-in piezoresistive cantilever varies according to the pressure change applied to the needle tip. Because the fabricated sensor responded to pseudo body pressure, it was suggested that the fabricated needle-type pressure sensor could detect pressure change inside the body.

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Multi-Axial Tactile Sensor Using Standing Lig Cantilevers on Polyimide Film

R Nakashima, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 688 - 690 2022

ISSN 1084-6999

This paper reports a multi-axial tactile sensor using standing laser-induced graphene (LIG) cantilevers. The fabrication process of the proposed sensor element involves only one irradiating of each of the two types of lasers. Additionally, since the LIG cantilevers are formed on a flexible polyimide (PI) film, the cantilever can be easily kept in a standing position via thermoplastic deformation. As a result, the prototype dual axial sensor realized the measurement of normal and shear stresses with high independence.

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Light harvesting self-powered strain sensor using 3C-SiC/Si heterostructure

T Nguyen, D Van Nguyen, H Nguyen, B Tong, CD Tran, H Takahashi, ...

2022 IEEE Sensors, 1-4 (Proceedings of IEEE Sensors) 2022-October 2022

ISSN 1930-0395

Herein we report a light harvesting self-powered strain sensor using a monolithic heterojunction structure. Firstly, a strain sensor in a geometry of a cantilever with a 3C-SiC/Si heterojunction sensing element is fabricated. Secondly, light energy harvesting ability of the strain sensor is demonstrated under illumination of a commercial LED. Finally, the performance of the sensor under the self-powered mode is evaluated by inducing strain in the sensing element and simultaneously monitoring the change of converted electrical energy. Under illumination of LED with light power of 428 μW, the generated photovoltage is as high as approximately 16.4 mV. The sensor can harvest light energy convert it into electrical energy to power itself and sense the strain ranging from 200 ppm to 700 ppm with a sensitivity of approximately 0.06 μV /ppm.

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Angular Accelerometer with Integrated Liquid Spiral Channel and lig Sensing Element on Polyimide Film

R Nakashima, H Takahashi

2022 IEEE 35th International Conference on Micro Electro Mechanical Systems … (IEEE Symposium on Mass Storage Systems and Technologies) 2022-January 747 - 749 2022

ISSN 1084-6999

This paper reports on the fabrication method of an angular accelerometer with integrated liquid spiral channels and laser-induced graphene (LIG) sensing element. The proposed fabrication process forms the LIG sensing element and the spiral grooves via a CO2 laser and a UV laser, respectively, on a polyimide (PI) film. The liquid-sealed spiral channels are fabricated by filling the grooves with silicone oil and applying parylene deposition. Thus, the fabrication process is quite ple. The prototype sensor was validated for its response to angular acceleration.

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An experiment to distinguish persistent infrasounds from two fumaroles at Kirishima Iwo-Yama

K Yamakawa, M Ichihara, D Muramatsu, T Matsushima, H Takahashi, ...

2022

A Tunable Open Planar Acoustic Notch Filter Utilizing a Pneumatically Modulated Helmholtz Resonator Array

F Mizukoshi, H Takahashi

IEEE Access 10, 118213-118221 (IEEE Access) 10 118213 - 118221 2022

ISSN 2169-3536

Acoustic filters provide sound insulation unpleasant noises at a specific frequency only. Ordinary passive acoustic filters made up of acoustic metamaterial structures can work without a power supply. However, their working frequency is not adjustable. This study reports a tunable open planar acoustic notch filter that incorporates a pneumatically controlled Helmholtz resonator (HR) array. The HR array consisted of three layers: cavities, a membrane, and microchannels. The cavities function as the HR chambers, whose volume determines the resonant frequency. The acoustic wave is effectively attenuated at this frequency owing to the HR effect. The HR chamber volume can be varied by displacing the stretchable membrane with air pressure through the microchannels. This helps in adjusting the resonant frequency, thereby realizing a tunable acoustic notch filter. We conducted theoretical, and experimental examinations along with simulations of the frequency response for an HR array with three different cavity thicknesses. The prototype device realized a frequency tuning of approximately 4.1-4.9 kHz with 10 dB filtering. Furthermore, an improved notch frequency tunability was observed for the thinner cavities, along with a decrease in the notch performance. Thus, the proposed HR array filter can be useful for high-frequency noise that is generally uncomfortable for humans.

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Needle type pressure sensor using MEMS piezoresistive cantilever

T KISHIMOTO, H TAKAHASHI

センサ・マイクロマシンと応用システムシンポジウム (CD-ROM) 39, 2-3 2022

力センサの研究開発とその応用 [塾内限定]

H Takahashi

慶應義塾大学理工学部 2022

Force plate with simple mechanical springs and separated noncontact sensor elements

Y Kawasaki, A Ogawa, H Takahashi

Sensors 21 (21), 7092 (Sensors) 21 ( 21 ) 2021.11

ISSN 14248220

This paper reports on a force plate (FP) using mechanical springs and noncontact distance sensors. The ground reaction force (GRF) is one of the factors for clarify biomechanics, and FPs are widely used to measure it. The sensor elements of conventional FPs are mainly strain gauges. Thus, the mechanical properties of FP depend on the sensor element performance. If the FP performance must change, we must redesign the FP, including changing the sensor elements. Here, we proposed an FP that uses a measuring principle based on simple springs and noncontact sensors. The shape and performance of the proposed FP are expected to change easily. As a prototype device, we designed and fabricated an FP installed with 12 springs and four sensors for human walking. A planar coil and magnet were used as the sensor elements, and the sensor output was proportional to the vertical and horizontal displacements. The FP resonance frequency was 123 Hz, which was larger than the required specification. The calibration experiments showed that vertical and horizontal forces and moments could be measured independently. The FP’s resolutions were 1.9 N and 1.4 N in the anterior–posterior and vertical directions, respectively. Furthermore, the fabricated FP measured GRF similarly to the commercial FP when a human walked on the plate. These results suggest that the proposed method will be helpful for FPs with custom-made requirements.

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Acoustic notch filtering earmuff utilizing Helmholtz resonator arrays

F Mizukoshi, H Takahashi

PloS one 16 (10), e0258842 (PLoS ONE) 16 ( 10 ) 2021.10

ISSN 1932-6203

In recent years, noisy bustling environments have created situations in which earmuffs must soundproof only specific noise while transmitting significant sounds, such as voices, for work safety and efficiency. Two sound insulation technologies have been utilized: passive noise control (PNC) and active noise control (ANC). However, PNC is incapable of insulating selective frequencies of noise, and ANC is limited to low-frequency sounds. Thus, it has been difficult for traditional earmuffs to cancel out only high-frequency noise that people feel uncomfortable hearing. Here, we propose an acoustic notch filtering earmuff utilizing Helmholtz resonator (HR) arrays that provides a sound attenuation effect around the tuneable resonant frequency. A sheet-like sound insulating plate comprising HR arrays is realized in a honeycomb structure. Since the resonant frequency is determined by the geometry of the HR arrays, a highly audible sound region can be designed as the target frequency. In this research, the acoustic notch filtering performance of the proposed HR array plate is investigated in both simulations and experiments. Furthermore, the fabricated earmuffs using the novel HR array plates achieve a sound insulation performance exceeding 40 dB at the target frequency, which is sufficiently high compared to that of conventional earmuffs. The experimental results confirm that the proposed device is a useful approach for insulating frequency-selective sound.

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Pitot-static-tube-based waterflow sensor for marine biologging via inside sealing of an incompressible liquid

T Kishimoto, R Saito, H Tanaka, H Takahashi

IEEE Sensors Journal 21 (18), 19806-19814 (Institute of Electrical and Electronics Engineers ({IEEE})) 21 ( 18 ) 19806 - 19814 2021.09

ISSN 1530-437X

This article presents a waterflow sensor for marine biologging. Although biologging methods have attracted attention in evaluating marine animals' swimming performance, it has been difficult to directly measure the long-term waterflow velocity against a swimming animal. This is because the sensors require strict specifications, such as sufficient sensitivity and accuracy, small size and light weight, ability to move between water and air for breathing, and sufficient water pressure resistance. Here, we propose a waterflow sensor based on a closed-inlet Pitot-static tube structure that satisfies these requirements. The tube is filled with incompressible liquid. Silicone membranes are attached to the inlets to prevent air bubble infiltration. A differential pressure sensor chip, which works as the Pitot-static tube's sensing element, is built into the tube housing to measure the pressure difference between the inlets. Due to the fluid incompressibility, the required pressure resistance is realized. The developed sensor responded to waterflow from 0.2 m/s to 1.6 m/s with sufficiently high sensitivity. Therefore, the proposed sensor can be utilized for the biologging of marine animals.

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Seabird biologging system with compact waterproof airflow sensor

H Takahashi, M Naruoka, Y Inada, K Sato

Journal of Robotics and Mechatronics 33 (3), 466-474 (Journal of Robotics and Mechatronics) 33 ( 3 ) 466 - 474 2021.06

ISSN 0915-3942

This paper presents a seabird biologging system with a compact waterproof airflow sensor. Although biolog-ging methods have attracted attention in the evaluation of seabird flight performance, a direct measurement method of airflow velocity has not yet been es-tablished. When an airflow sensor is added to a bi-ologging system, a more accurate assessment of the flight performance can be obtained. We developed a compact Pitot tube-type airflow sensor that is special-ized for seabird biologging systems. Here, we integrated micro electro mechanical system (MEMS) sensor chips and a sensing circuit into the Pitot tube hous-ing. Then, we conducted a wind tunnel experiment using a stuffed seabird and the fabricated sensor. The results confirmed that the sensor responds to the wind speed even when attached to the dorsal surface of the seabird. Based on the above, we believe that the proposed sensor can be applied to practical seabird bi-ologging systems.

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Biaxial angular acceleration sensor with rotational-symmetric spiral channels and MEMS piezoresistive cantilevers

R Nakashima, H Takahashi

Micromachines 12 (5), 507 (Micromachines) 12 ( 5 ) 2021.05

Angular acceleration sensors are attracting attention as sensors for monitoring rotational vibration. Many angular acceleration sensors have been developed; however, multiaxis measurement is still in a challenging stage. In this study, we propose a biaxial angular acceleration sensor with two uniaxial sensor units arranged orthogonally. The sensor units consist of two rotationalsymmetric spiral channels and microelectromechanical system (MEMS) piezoresistive cantilevers. The cantilever is placed to interrupt the flow at the junctions of parallelly aligned spirals in each channel. When two cantilevers are used as the resistance of the bridge circuit in the two-gauge method, the rotational-symmetric spiral channels enhance the sensitivity in the target axis, while the nontarget axis sensitivities are canceled. The fabricated device responds with approximately constant sensitivity from 1 to 15 Hz, with a value of 3.86 × 10-5/(rad/s2), which is equal to the theoretical value. The nontarget axis sensitivity is approximately 1/400 of the target axis sensitivity. In addition, we demonstrate that each unit responds according to the tilt angle when the device is tilted along the two corresponding rotational axis planes. Thus, it is concluded that the developed device realizes biaxial angular acceleration measurement with low crosstalk.

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An angular accelerometer with high sensitivity and low crosstalk utilizing a piezoresistive cantilever and spiral liquid channels

B Jo, H Takahashi, T Takahata, I Shimoyama

IEEE Sensors Journal 21 (3), 2687-2692 (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC) 21 ( 3 ) 2687 - 2692 2021.02

ISSN 1530-437X

This article describes an angular accelerometer with high sensitivity and low crosstalk that uses a MEMS (Micro Electro Mechanical Systems) piezoresistive cantilever and spiral liquid channels. The fabricated device is composed of two spiral channels aligned in parallel with the piezoresistive cantilever placed in between the channels. When angular acceleration is applied, the liquid inside the spiral channels produces an inertial force. This inertial force generates a pressure difference between the spiral channels, and that difference is measured by a piezoresistive cantilever with a high resolution of 0.01 Pa. The pressure difference causes deformation of the piezoresistive cantilever which results in resistance change. Finally, the applied angular acceleration can be calculated from the resistance change. By increasing the number of turns of the spiral channel, both high sensitivity and low crosstalk from the nontarget axis can be achieved. Our proposed device with 12.5 turns achieved a sensitivity of 0.72 mV/(rad/s(2)) and crosstalk of less than 2%.

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Compact Pitot-static-tube-based waterflow sensor for biologging of marine animals

T Kishimoto, R Saito, H Tanaka, H Takahashi

2021 IEEE Sensors, 1-4 (Proceedings of IEEE Sensors) 2021-October 2021

ISSN 1930-0395

This study presents a waterflow sensor for biologging of marine animals. Although a biologging method of recording animal behavior with sensors is attracted attention for evaluating the swimming performance of marine animals, it is not easy to measure waterflow velocity for a long time. This is due to strict requirements such as compact size and high pressure resistance. In addition, marine animals move above the sea surface to breathe. Here, we proposed a compact Pitot-static-tube-based waterflow sensor for biologging of marine animals. Incompressible liquid is sealed inside the sensor housings to realize high-pressure resistance. A thin film is glued inlets of the sensor to prevent air bubbles invention. A membrane-type differential pressure sensor chip is built inside the sensor to measure differential pressure between each inlet. By downsizing the sensor shape and reducing sealed incompressible liquid, the sensor is compacter than a previous sensor. The developed sensor responded to waterflow velocity from 0.2 to1.6 m/s with sufficiently high sensitivity.

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Densely Arrayed Active Antennas Embedded in Vertical Nanoholes for Backside-Illuminated Silicon-Based Broadband Infrared Photodetection

Shun Yasunaga, Hidetoshi Takahashi, Tomoyuki Takahata, Isao Shimoyama, Tetsuo Kan

ADVANCED MATERIALS INTERFACES (WILEY) 7 ( 21 ) 2020.11

ISSN 2196-7350

Plasmonic metal nanoantennas arrayed on silicon have attracted attention as silicon-based sub-bandgap infrared detectors. Localized surface plasmons induced on metal nanoblocks can provide a broadband responsivity, and the silicon-based configuration offers the potential for complementary metal oxide semiconductor-compatible infrared photodetectors. The responsivity of such devices, however, needs further improvement. In this report, a nanoantenna structure consisting of a nanoblock with electrical connection to it built in a narrow, vertical, and deep nanohole is presented, which generates a photocurrent in response to backside illumination. Inclined evaporative deposition of copper onto an array of nanoholes, 150 nm in diameter and 560 nm in depth, simultaneously forms nanoblocks and thin conductive films. The structure's effectiveness is demonstrated from the reflectance and responsivity to infrared laser illumination 1.1-1.8 mu m in wavelength. When the periodicity of the nanoholes is 500 nm, a responsivity of 9.8 mA W(-1)at 1.55 mu m is obtained, which is sustained over a broad band. The responsivity-density relationship has a limitation between periodicities of 250 and 500 nm, possibly because of overlapped near fields around antennas and the resultant altered resonant mode. With its simple fabrication and efficient functionality, the nanoantenna structure contributes to the realization of silicon-based infrared imaging.

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MEMS triaxial gyroscope using surface and sidewall doping piezoresistors

H Takahashi, K Abe, T Takahata, I Shimoyama

Journal of Micromechanics and Microengineering 30 (10), 105012 (IOP PUBLISHING LTD) 30 ( 10 ) 2020.10

ISSN 0960-1317

This paper describes a MEMS triaxial gyroscope utilizing three-dimensional piezoresistive elements. MEMS gyroscopes are widely used for robot motion control, drones, mobile phones and so on. Although a piezoresistive sensing element has the potential for high sensitivity to angular velocity via vibrations that occur due to the Coriolis force, a commonly used piezoresistor, which is formed on a device surface, is not suitable to measure in-plane deformations. Thus, it is difficult to realize a sensing element for a triaxial gyroscope with conventional piezoresistors, especially an element for the detection of vertical axis angular velocity. Here, we propose a triaxial gyroscope utilizing surface and sidewall doping piezoresistors as the sensing element. The surface and sidewall doping piezoresistors detect out-of-plane and in-plane vibrations due to the corresponding three-dimensional Coriolis forces, respectively. As a result, the triaxial angular velocity becomes measurable. The experimental results show that the fabricated gyroscope responds to three-dimensional angular velocities with low crosstalk. Therefore, the proposed gyroscope is suitable for practical angular velocity measurement applications.

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Multidirectional UV lithography via inclined/rotated mirrors for liquid materials

T Sugimito, H Takahashi

Applied Physics Express 13 (7), 076502 (Applied Physics Express) 13 ( 7 ) 2020.07

ISSN 1882-0778

This letter presents the development of an exposure equipment for inclined/rotating lithography with UV curable liquid materials. The proposed equipment is composed of inclined mirrors rotating around exposure spot and shading plate to prevent direct vertical irradiated UV light. UV light ray is reflected on the mirrors, and irradiate to the spot with inclined angle via rotation. During mirrors rotating, UV curable material located on the exposure spot keeps a quiet state. The incident angle of UV light ray is controllable by changing the mirror inclination. We developed an equipment and conducted an experiment for the fabrication of 3D structures with PEGDA.

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Time response characteristics of a highly sensitive barometric pressure change sensor based on MEMS piezoresistive cantilevers

R Wada, H Takahashi

Japanese Journal of Applied Physics 59 (7), 070906 (Japanese Journal of Applied Physics) 59 ( 7 ) 2020.07

ISSN 0021-4922

This paper describes the frequency characteristics of a highly sensitive barometric pressure change sensor. Here, we propose a method to measure pressure changes based on microelectromechanical systems piezoresistive cantilevers and an air chamber. The proposed sensor structure realizes a mechanical high pass filter to eliminate the influence of the barometric pressure change due to meteorological variations. The experimental frequency characteristics indicate that the proposed sensor unit with a high resolution of less than 0.1 Pa from 0.1 to 10 Hz responds to pressure changes with a high pass filter property according to the chamber volume size.

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Self-focusing 3D lithography with varying refractive index polyethylene glycol diacrylate

H Takahashi, T Kan, G Lee, N Dönmez, J Kim, J Park, D Kim, YJ Heo

Applied Physics Express 13 (7), 076503 (IOP PUBLISHING LTD) 13 ( 7 ) 2020.07

ISSN 1882-0778

This work presents self-focusing 3D lithography based on the refractive index changes of polyethylene glycol diacrylate (PEGDA) during photopolymerization. Since the polymerization of PEGDA leads to an increase in the refractive index, the UV light rays in the PEGDA undergo a refraction effect during exposure, thus being focused and forming 3D photopolymerized structures. We demonstrate the potential of self-focusing 3D lithography by fabricating PEGDA microneedles and trapezoid-shaped microwells. Their structures well match our theoretical estimation. Therefore, our theoretical approach can provide a short route to realizing on-demand, complicated 3D structures of refractive-index-variable materials with single UV exposure.

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Micro Water Flow Measurement Using a Temperature-Compensated MEMS Piezoresistive Cantilever

R Pommois, G Furusawa, T Kosuge, S Yasunaga, H Hanawa, ...

Micromachines 11 (7), 647 (MDPI) 11 ( 7 ) 2020.07

In this study, we propose a microelectromechanical system (MEMS) force sensor for microflow measurements. The sensor is equipped with a flow sensing piezoresistive cantilever and a dummy piezoresistive cantilever, which acts as a temperature reference. Since the dummy cantilever is also in the form of a thin cantilever, the temperature environment of the dummy sensor is almost identical to that of the sensing cantilever. The temperature compensation effect was measured, and the piezoresistive cantilever was combined with a gasket jig to enable the direct implementation of the piezoresistive cantilever in a flow tube. The sensor device stably measured flow rates from 20 mu L/s to 400 mu L/s in a silicon tube with a 2-mm inner diameter without being disturbed by temperature fluctuations.

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Reconfigurable Surface Plasmon Resonance Photodetector with a MEMS Deformable Cantilever

M Oshita, H Takahashi, Y Ajiki, T Kan

ACS Photonics (American Chemical Society (ACS)) 7 ( 3 ) 673 - 679 2020

ISSN 2330-4022

Plasmonic photodetectors have many useful characteristics, such as wavelength- or polarization-specific photodetection. Although reconfigurable plasmonic structures have been intensively studied, reconfiguration of the optical characteristics of a plasmonic photodetector has not yet been reported. Here, we report a gold diffraction-grating-type plasmonic photodetector that reconfigures its optical characteristics with a MEMS deformable cantilever. By reconfiguring the photodetector characteristics using an angular scan of the cantilever over -21° to 21°, the peak shifts of the photocurrent signal waveform are found to depend on the wavelength over 1200∼1500 nm, which is consistent with SPR theory. The proposed reconfigurable plasmonic photodetector allowed us to obtain spectroscopic information on the light in a demonstration experiment.

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Pipette Based Viscometer with Pressure Sensor Element

S Cho, TV Nguyen, N Miki, H Takahashi

2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2020-January 646 - 648 2020

ISSN 1084-6999

© 2020 IEEE. This paper reports a simple viscometer, whose principle utilizes the relationship between liquid viscosity and the suction speed in a tube. The proposed viscometer is composed of an air chamber and a glass tube. A steel ball is attached to the silicone membrane of the chamber and an electromagnetic magnet is used to provide the volume change. A MEMS pressure sensor element is attached to the chamber to measure its pressure change. When a step-response volume change is applied, the chamber pressure decreases so that the liquid sticking to the tube gradually ascends at a speed depending to the viscosity. Thus, the viscosity can be calculated by measuring the gradient of the pressure change. The proposed method can be applied to micropipettes so that viscosity is easily measured with a simple device.

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Direct Fabrication of PEGDA Micro Suction Cup Array Using Inclined/Rotating Mirror Exposure System

T Sugimoto, H Takahashi

ISSN 1084-6999

This paper reports on direct fabrication method of a PEGDA micro suction cup array. A micro suction cup has been attracted in many application, however, conventional fabrication method using mold has limitation of the shape of the fabricated structure. The proposed fabrication method realizes a micro suction cup array with single exposure dose by inclined/rotating exposure system. As the suction cup material, UV curable Poly (ethylene glycol) diacrylate (PEGDA) is used due to its suitable characteristics. By controlling the inclined angle and mask pattern, the shape of micro suction cup can be designed. We conducted fabrication experiment of suction cup array of 200 mumathrm{m} in diameter to confirm our proposed method is useful.

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Densely Arrayed Active Antennas Embedded in Vertical Nanoholes for Backside‐Illuminated Silicon‐Based Broadband Infrared Photodetection

S Yasunaga, H Takahashi, T Takahata, I Shimoyama, T Kan

Advanced Materials Interfaces 7 (21), 2001039 2020

3D Hydrogel Manufacturing Employing Self-Focusing During Photo-Curing Process

G Lee, H Takahashi, T Kan, J Kim, N Donmez, J Park, D Kim, S Ka, ...

2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems … (Institute of Electrical and Electronics Engineers Inc.) 2020-January 323 - 324 2020

ISSN 1084-6999

This work proposes a 3D lithography technique with self-focusing during polymerization based on refractive-indices change of polyethylene glycol diacrylate (PEGDA) (Fig. 1). Compared to the previous work, the present work enables to fabricate 3D structures using single UV exposure and theoretically estimate 3D features. We demonstrate the potential of the self-focusing 3D lithography by fabricating PEGDA microneedles and trapezoid-shaped wells. Their structures well match to our theoretical estimation. Therefore, our theoretical approach shows its potential for on-demand, complicated 3D structures of refractive-indices-variable materials with single UV exposure.

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Assessment of the risk of malnutrition due to aspiration pneumonia and oral feeding difficulty

S Sato, H Takahashi

Nutrición hospitalaria: Órgano oficial de la Sociedad Española de Nutrición … 2020

Applicability of Plasmonic Photodetectors with Dynamic Reconfiguration of Detectable Wavelength for Spectroscopy

Oshita Masaaki, Takahashi Hidetoshi, Ajiki Yoshiharu, Kan Tetsuo

The Proceedings of the Symposium on Micro-Nano Science and Technology (The Japan Society of Mechanical Engineers) 2020.11 27P3-MN3-6 2020

This paper reports a reconfigurable plasmonic photodetector with a micro electro mechanical system (MEMS) angular modulator for application of miniaturization of a near-infrared spectrometer. The structure of this research has a plasmonic gold diffraction grating capable of detecting the corresponding wavelength at a specific incident angle on an n-type Si cantilever. We confirmed that the peak of the photocurrent signal from the fabricated device occurred at different incidence angles depending on the wavelength. To demonstrate the applicability of the photodetector, spectroscopy was performed from the photocurrent signals from the device. The spectra calculated from the signals was consistent with the spectra from the commercial spectrometer.

A MEMS-based measurement system for evaluating the force-length relationship of human induced pluripotent stem cell-derived cardiomyocytes adhered on a substrate

K Matsudaira, H Takahashi, KH Shoji, TV Nguyen, T Tsukagoshi, ...

Journal of Micromechanics and Microengineering (IOP PUBLISHING LTD) 29 ( 5 ) 2019

ISSN 09601317

© 2019 IOP Publishing Ltd. This paper reports on a method for evaluating the force-length relationship of adhering human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) on the substrate using a measurement system comprising of a micromachined movable plate and a piezoresistive force probe. The cells on the plate are stretched by pushing the movable plate with the piezoresistive cantilever, which is actuated by a piezo stage. The twitch forces and the applied stretch are measured quantitatively with the piezoresistive cantilever. The results demonstrated that the twitch forces of the hiPSC-CMs increased when a stretch was applied. This evaluation method improves the understanding of the intrinsic force-length relationship of hiPSC-CMs at the cellular scale.

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Sensor

I Shimoyama, K Matsumoto, BK Nguyen, H Takahashi, MD Nguyen, ...

US Patent App. 10/234,429 2019

Highly sensitive and low-crosstalk angular acceleration sensor using mirror-symmetric liquid ring channels and MEMS piezoresistive cantilevers

H Takahashi, T Kan, A Nakai, T Takahata, T Usami, I Shimoyama

Sensors and Actuators A: Physical 287, 39-47 (ELSEVIER SCIENCE SA) 287 39 - 47 2019

ISSN 09244247

© 2019 This paper describes an angular acceleration sensor that uses liquid ring channels and piezoresistive cantilevers. The detection of fluidic rotation has attracted attention as a sensing principle for angular acceleration due to the simple structure and potentially low power consumption of devices that use said principle. Although the existing angular acceleration sensors that use this sensing principle have the potential for high sensitivity to angular acceleration about the target axis, crosstalk is an issue—specifically, crosstalk with angular accelerations about other axes and with linear acceleration. Here, we propose an angular acceleration sensor that uses a MEMS piezoresistive cantilever as the sensing element and two mirror-symmetric ring channels. This mirror symmetry cancels out the signals due to accelerations about the other axes, while the signal for the angular acceleration about the target axis is doubled. The experimental results show that the sensitivity to other axial angular accelerations and linear acceleration is sufficiently small. The obtained sensitivity for the angular acceleration is as high as 3.1 × 10 −4 (rad/s 2 ) -1 , similar to theoretical predictions. This value for the sensitivity is maintained over a range of frequencies from 0.1 Hz to 100 Hz. Therefore, the proposed sensor is suitable for practical angular acceleration detection applications.

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Underwater Pitot Tube for Swimming Animals

T Hagiwara, H Takahashi, TV Nguyen, T Takahata, I Shimoyama

2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2019-January 95 - 98 2019

ISSN 9781728116105

© 2019 IEEE. This paper reports on an underwater Pitot tube which is designed for swimming measurement of marine animals. The tubes of the Pitot tube are filled with incompressive liquid and sealed by thin films so that the device can be used even when plunged into water. The Pitot tube has a pressure sensor inside that consists of a piezoresistive cantilever incorporated into a thin Parylene-C membrane. When a water flow is applied to the Pitot tube, the thin films at the inlets act as elastic membranes and the liquid filled in the tubes transmits the pressure to the pressure sensor. The proposed Pitot tube can be used as a water flow speedometer for biological studies of marine animals.

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An MRI-Compatible Force Sensor with Enclosed Air Using Pressure Transmission

D Akutagawa, T Izumizaki, M Hori, H Takahashi, I Shimoyama, T Dohi

2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2019-January 803 - 806 2019

ISSN 9781728116105

© 2019 IEEE. We fabricated an MRI-compatible force sensor with enclosed air using pressure transmission. The fabricated force sensor consists of a contact portion, sensing portions, and connecting pipes. When force was applied to the contact portion, the internal air pressure increased with a deformation of the contact portion, and is transmitted to the sensing portion through the connecting pipes. In the sensing portion, the change in air pressure is detected by a change in the resistance of a piezoresistive cantilever. Since using this air pressure transmission, the sensing portion can be placed away from the magnet of the MRI. Therefore, the force sensor does not interfere with the magnetic field, and it can be used in the magnet of an MRI.

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Highly Sensitive Angular Accelerometer Utilizing Piezoresistive Cantilever and Spiral Liquid Channel

B Jo, H Takahashi, T Takahata, I Shimoyama

ISSN 9781728116105

© 2019 IEEE. This paper reports a highly sensitive angular accelerometer utilizing a piezoresistive cantilever and spiral liquid channels. The spiral structure increases the total inertial force of liquid due to angular acceleration, which leads to the sensitivity enhancement. The differential pressure between two spiral liquid channels was measured by a piezoresistive cantilever with the resolution of 0.01 Pa. The developed sensor with number of turns of the spiral with 25 achieved the sensitivity enhancement by 28.5 times, compared to the ring channel sensor.

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In-Plane Gyroscope Using a Piezoresistive Beams with Sidewall Doping

K Abe, H Takahashi, T Takahata, I Shimoyama

ISSN 9781728116105

© 2019 IEEE. This paper reports a gyroscope using sidewall doped piezoresistors and vibrating mass by Lorentz force. With sidewall doped piezoresistors, in-plane deformation of the beams due to Coriolis force generated by angular motion can be detected, which was difficult with surface doped piezoresistors. The proposed gyroscope was designed so that the resonant frequencies of the driving and sensing modes were similar to each other. It was demonstrated that the developed gyroscope measured angular velocity through the resistance change of the piezoresistive beams.

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Infrared Photodetector with Copper Resonator in Silicon Nanohole Array

S Yasunaga, T Kan, H Takahashi, T Takahata, I Shimoyama

2019 20th International Conference on Solid-State Sensors, Actuators and … (2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII) 633 - 636 2019

ISSN 9781728120072

© 2019 IEEE. A silicon-based infrared photodetector with metal nanostructures has been drawing attention, while lacking sufficient responsivity. We hereby present a silicon-based infrared photodetector furnished with an array of a nano-scale copper plate which induces localized surface plasmon resonance (LSPR). Each plate is placed at the bottom of a nanohole on a silicon substrate. This device possesses two features: electrically-connected copper resonators and backside-illuminating configuration. They lead to efficient photocurrent generation. As LSPR couples with vertically incident light, this structure can be a solution of realizing a silicon-based infrared photodetector that can be adapted to prevalent semiconductor devices.

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Monitoring Volcanic Activity with High Sensitive Infrasound Sensor Using a Piezoresistive Cantilever

J Shimatani, H Takahashi, M Ichihara, T Takahata, I Shimoyama

ISSN 9781728116105

© 2019 IEEE. In this paper, we propose a high sensitive monitoring method of infrasound evoked by a volcano eruption. The sensor unit is composed of two differential pressure sensors and an air chamber. The pressure resolution of the developed sensor is approximately 0.01 Pa, which is sufficiently small to detect the tiny infrasound. The measurable frequency range is from 0.3 Hz, which is sufficiently low for the infrasound. The sensor units were set at the foot of volcano, Sakurajima, Kagoshima, Japan. It was confirmed that the sensors kept the high sensitive monitoring performance for a month.

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Waterproof airflow sensor for seabird bio-logging using a highly sensitive differential pressure sensor and nano-hole array

Hidetoshi Takahashi, Akihito Nakai and Isao Shimoyama

Sensors & Actuators A: Physical (ELSEVIER SCIENCE SA) 281 243 - 249 2018.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 09244247

This paper presents an airflow sensor for seabird bio-logging. Although bio-logging methods have attracted attention in the evaluation of seabird flight performance, the airflow velocity has not been directly measured. Here, an airflow sensor is added to the bio-logging system, and a direct airflow velocity measurement is applied, thus enabling more accurate evaluation of the flight performance. To attach the sensor to the bio-logging system, the sensor must be waterproof because seabirds dive into the sea to prey on fish. In addition, the sensor must also be compact and have high sensitivity. Here, we propose a Pitot tube-type airflow sensor that satisfies these requirements. The proposed sensor is composed of microelectromechanical systems (MEMS) piezoresistive cantilevers as sensing elements with high sensitivity and anodic alumina membranes with a nano-hole array as the waterproof elements with airflow penetration. The developed sensor responded sufficiently to airflow velocities from 2 m/s to 20 m/s. In addition, the sensor maintained its sensitivity after plunging into the water and returning to the air. Therefore, the proposed sensor can be utilized for practical seabird bio-logging. (C) 2018 Elsevier B.V. All rights reserved.

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Experimental study of the aerodynamic interaction between the forewing and hindwing of a beetle-type ornithopter

Hidetoshi Takahashi, Kosuke Abe, Tomoyuki Takahata, Isao Shimoyama

Aerospace (Aerospace) 5 ( 3 ) 83 2018.08

Research paper (scientific journal), Joint Work, Accepted

© 2018 by the authors. Beetles have attracted attention from researchers due to their unique combination of a passively flapping forewing and an actively flapping hindwing during flight. Because the wing loads of beetles are larger than the wing loads of other insects, the mechanism of beetle flight is potentially useful for modeling a small aircraft with a large weight. In this paper, we present a beetle-type ornithopter in which the wings are geometrically and kinematically modeled after an actual beetle. Furthermore, the forewing is designed to be changeable between no-wing, flapping-wing, or fixed-wing configurations. Micro-electro-mechanical systems (MEMS) differential pressure sensors were attached to both the forewing and the hindwing to evaluate the aerodynamic performance during flight. Whether the forewing is configured as a flapping wing or a fixed wing, it generated constant positive differential pressure during forward flight, whereas the differential pressure on the hindwing varied with the flapping motion during forward flight. The experimental results suggest that beetles utilize the forewing for effective vertical force enhancement.

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薄膜メタマテリアル実現に向けたフレーム構造のTHz応答解析

磯崎瑛宏, 菅哲朗, 高橋英俊, 松本潔, 下山勲

電気学会論文誌E 138 ( 7 ) 281 - 286 2018.07

Research paper (scientific journal), Joint Work, Accepted

Development of a light source with a uniform intensity reinforced by a checkerboard half-mirror positioned within inverse L-shaped UV-LED arrays

Hidetoshi Takahashi, Isao Shimoyama and Yun Jung Heo

Applied Physics Express (Applied Physics Express) 11 ( 6 ) 066701 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 18820778

© 2018 The Japan Society of Applied Physics. This paper presents a simple, low-cost, long-lasting UV-LED-based light source with uniform light intensity using a checkerboard half-mirror positioned within inverse L-shaped UV-LED arrays. The light rays from the top UV-LED array passed through the transparent portions of the checkerboard half-mirror, while the light rays from the side UV-LED array were reflected on the remaining opaque portions at right angles. Thus, uniform light intensity was achieved on the bottom area. Using the developed UV-LED light source, we fabricated microstructures with uniform shapes on a large area, thereby showing feasible applications for MEMS fabrication.

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Silicon-based Nano-hole IR Detector with Supercritical Fluid Deposition of Copper

Yasunaga Shun, Takahashi Hidetoshi, Kan Tetsuo, Tsukagoshi Takuya, Momose Takeshi, Takahata Tomoyuki, Shimoyama Isao

JSAP Annual Meetings Extended Abstracts (The Japan Society of Applied Physics) 2018.1 3128 - 3128 2018.03

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Cellular dynamics of bovine aortic smooth muscle cells measured using MEMS force sensors

Takuya Tsukagoshi, Thanh-Vinh Nguyen, Kayoko Hirayama-Shoji, Hidetoshi Takahashi, Kiyoshi Matsumoto and Isao Shimoyama

Journal of Physics D: Applied Physics (Institute of Physics Publishing) 51 ( 14 ) 145401 2018.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 00223727

Adhesive cells perceive the mechanical properties of the substrates to which they adhere, adjusting their cellular mechanical forces according to their biological characteristics. This mechanical interaction subsequently affects the growth, locomotion, and differentiation of the cell. However, little is known about the detailed mechanism that underlies this interaction between adherent cells and substrates because dynamically measuring mechanical phenomena is difficult. Here, we utilize microelectromechamical systems force sensors that can measure cellular traction forces with high temporal resolution (∼2.5 μs) over long periods (∼3 h). We found that the cellular dynamics reflected physical phenomena with time scales from milliseconds to hours, which contradicts the idea that cellular motion is slow. A single focal adhesion (FA) generates an average force of 7 nN, which disappears in ms via the action of trypsin-ethylenediaminetetraacetic acid. The force-changing rate obtained from our measurements suggests that the time required for an FA to decompose was nearly proportional to the force acting on the FA.

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Spring constant measurement using a MEMS force and displacement sensor utilizing paralleled piezoresistive cantilevers

Sumihiro Kohyama, Hidetoshi Takahashi, Satoru Yoshida, Hiroaki Onoe, Kayoko Hirayama-Shoji, Takuya Tsukagoshi, Tomoyuki Takahata and Isao Shimoyama

Journal of Micromechanics and Microengineering (Institute of Physics Publishing) 28 ( 4 ) 045013 2018.02

Research paper (scientific journal), Joint Work, Accepted, ISSN 0960-1317

This paper reports on a method to measure a spring constant on site using a micro electro mechanical systems (MEMS) force and displacement sensor. The proposed sensor consists of a force-sensing cantilever and a displacement-sensing cantilever. Each cantilever is composed of two beams with a piezoresistor on the sidewall for measuring the in-plane lateral directional force and displacement. The force resolution and displacement resolution of the fabricated sensor were less than 0.8 μN and 0.1 μm, respectively. We measured the spring constants of two types of hydrogel microparticles to demonstrate the effectiveness of the proposed sensor, with values of approximately 4.3 N m-1 and 15.1 N m-1 obtained. The results indicated that the proposed sensor is effective for on-site spring constant measurement.

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Analysis of THz Response of Frame Structures for Achieving Thin-film-type Metamaterials

A Isozaki, T Kan, H Takahashi, K Matsumoto, I Shimoyama

IEEJ Transactions on Sensors and Micromachines 138, 281-286 (IEEJ Transactions on Sensors and Micromachines) 138 ( 7 ) 281 - 286 2018

ISSN 13418939

© 2018 The Institute of Electrical Engineers of Japan. In this paper, we report on analytical results of terahertz (THz)-wave response of frame structures that support a thin film where metamaterial elements exist. Since the transmittance spectra of the metamaterial including the support frames differ from those of the metamaterial elements excluding the frames, investigation of influences of the frames on the measured spectra is important. A preliminary analysis revealed that the spectra of the metamaterial elements are partially recovered by compensating the measured spectra using time-domain transmittance waves of a bulk silicon-on-insulator wafer, from which the support frames are made. We experimentally demonstrate that the spectra of the support frames depend on the width, but not on the pitch, of the frames. Moreover, we show that a slab-type waveguide model can explain the interference between the support frames and the incident THz waves. The physical mechanism of THz response of support frames, which are clarified in this article, will be helpful to design thin-film type metamaterials.

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Waterproof pitot tube with high sensitive differential pressure sensor and nano-hole array

H Takahashi, I Shimoyama

2018 IEEE Micro Electro Mechanical Systems (MEMS), 214-217 (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2018-January 214 - 217 2018

ISSN 9781538647820

© 2018 IEEE. This paper reports a Pitot tube type airflow sensor, which achieves both high sensitivity and water resistance. The proposed Pitot tube is composed of piezoresistive cantilevers as differential pressure sensing elements and nano-hole arrays as waterproof elements. The nano-hole arrays are attached to the air inlets, which are located the tip of the tube and sides of the sphere. When airflow is applied to the Pitot tube, air passes through the nano-hole arrays, and differential pressure between two inlets acts on the piezoresistive cantilevers. On the other hand, when locating in water, the nano-hole arrays protect the water penetration into the tube. The Pitot tube will be used for the airspeed measurement of flying marine birds.

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Miniaturization of a grating-based SPR type near-infrared spectrometer by using vibration of a MEMS cantilever

M Oshita, H Takahashi, T Kan

2018 IEEE Micro Electro Mechanical Systems (MEMS), 688-691 (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2018-January 688 - 691 2018

ISSN 9781538647820

© 2018 IEEE. This paper reports on a miniaturization method of near-infrared spectrometer based on a plasmonic near-infrared photodetector. The spectrometer has an n-typed Si cantilever with an Au diffraction grating for Surface Plasmon Resonance (SPR) generation. Mechanical vibration of the cantilever provides alternation of the angle of incidence of the light to be measured. Coupled to SPR, the light energy is transduced to photocurrent. Since the different incident angle corresponds to different SPR resonant wavelength, the electrical measurement data of photocurrent during the cantilever vibration provides the whole spectrum information of the incident light. In this time, we developed a spectrometer device and measured time varying series of photocurrent during the cantilever vibration. Waveforms of the series were clearly dependent on the incident wavelength, and coherent to the SPR theory.

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Load dependency measurement of IPS cell-derived cardiomyocytes' contraction

K Matsudaira, H Takahashi, KH Shoji, TV Nguyen, T Tsukagoshi, ...

2018 IEEE Micro Electro Mechanical Systems (MEMS), 129-132 (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2018-January 129 - 132 2018

ISSN 9781538647820

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High sensitive and large area force plate for ground reaction force measurement of ant running

S Kohyama, H Takahashi, T Takahata, I Shimoyama

2018 IEEE Micro Electro Mechanical Systems (MEMS), 874-877 (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2018-January 874 - 877 2018

ISSN 9781538647820

© 2018 IEEE. This paper reports on a MEMS force plate for measurement of total ground reaction force (GRF) of an ant during running. To achieve both high force sensitivity and ensuring area for ant running with several steps, the MEMS force plate consisted of two cantilever chips and one plate which were fabricated separately. The force plate was designed to measure vertical directional force with the force resolution under 0.5 μΝ. Using the fabricated MEMS force plate, we measured the GRF of Messor aciculatus. The results showed that the fluctuation of the ground reaction force was 3.7 % to the body weight of the ant.

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Ground effect measurement of butterfly take-off

T Hagiwara, H Takahashi, T Takahata, I Shimoyama

2018 IEEE Micro Electro Mechanical Systems (MEMS), 832-835 (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2018-January 832 - 835 2018

ISSN 9781538647820

© 2018 IEEE. This paper reports on a measurement of ground effect during a butterfly taking-off. We developed a differential pressure sensor array and a force plate to measure the pressure distribution on the ground and jumping force of legs, respectively. The force caused by the ground effect was evaluated as the integration of the pressure distribution. The aerodynamic force of wings was obtained from the jumping force and the acceleration of the taking-off motion. The acceleration was obtained from high-speed camera images. The result showed that the force on the ground was approximately 40% of the aerodynamic force.

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Cantilever pressure sensor with division portions for dividing lever resistance and having piezoresistor element

I Shimoyama, K Matsumoto, H Takahashi, MD Nguyen, T Uchiyama, ...

US Patent 9,995,642 2018

MEMS-based pressure sensor with a superoleophobic membrane for measuring droplet vibration

TV Nguyen, H Takahashi, I Shimoyama

2017 19th International Conference on Solid-State Sensors, Actuators and … (TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems) 1152 - 1155 2017

ISSN 9781538627310

© 2017 IEEE. We report on a sensor design to measure the vibration of small droplets. The sensor consists of a piezoresistive cantilever and a chamber covered with a superoleophobic membrane. The vibration of a droplet on the membrane causes the pressure of the chamber to change. Since the cantilever is able to detect a pressure change of less than 0.1 Pa, the vibration of the droplet can be precisely measured by the cantilever. In comparison to previously developed MEMS-based force sensor to measure the droplet vibration, the current sensor design offers several benefits including: wide range of usable liquids, simple sensing scheme (only one sensor is required) and capability to be disposable. With these advantages, our method is believed to be useful in measuring viscosity of small droplet for point-of-care application.

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A wall shear stress sensor using a pair of sidewall doped cantilevers

TV Nguyen, R Kazama, H Takahashi, T Takahata, K Matsumoto, ...

Journal of Micromechanics and Microengineering 27 (7), 075017 (IOP PUBLISHING LTD) 27 ( 7 ) 075017 2017

Research paper (scientific journal), Joint Work, Accepted, ISSN 09601317

In this paper, we report on a micro-electro mechanical system (MEMS)-based piezoresistive sensor for measuring shear stress induced by an airflow. The advantages of the proposed sensor include a simple sensing method and a high resonance frequency due to the small size of the sensing elements. Our sensor consists of a pair of 3 mu m thick cantilevers with piezoresistors formed on the sidewall of their hinges to detect lateral deformation in the cantilevers induced by an airflow. Each cantilever has a 200 mu m x 400 mu m plate supported by two 150 mu m long, 4 mu m wide beams. The piezoresistors on the two cantilevers are designed to deform in opposite manners when a shear stress is applied and in the same manner when a pressure is applied. Therefore, the applied shear stress can be detected from the difference in the responses of the two cantilevers without becoming conflated with pressure. In this paper, the design, fabrication and evaluation of the proposed sensor are reported and compared to numerical simulation results. From the experimental results, the resolution of the sensor and its first resonance frequency are 1.3 Pa and 3.9 kHz, respectively. Moreover, we show that the effect of temperature on the readout of the sensor can be eliminated using a temperature-compensating piezoresistor fabricated on the same sensor chip. Finally, using the fabricated sensor, the measurement of the shear stress induced by an airflow with velocity between -10 and 10 m s(-1) is demonstrated.

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Uniform areal-distribution of UV intensity by synchronizing signal-waveforms and position of a UV-LED array

H Takahashi, I Shimoyama, YJ Heo

Applied Physics Letters 111 (26), 263503 (AMER INST PHYSICS) 111 ( 26 ) 263503 2017

Research paper (scientific journal), Joint Work, Accepted, ISSN 00036951

This paper describes a theoretical approach to give an irradiated area a uniform distribution of LED light intensity by synchronizing the signal waveforms and position control of the LEDs. Although UV-LEDs have attracted considerable attention as alternative light sources for ultraviolet (UV) lithography in Micro Electro Mechanical Systems (MEMS) fabrication, mainly because of their low cost and low power consumption, the realization of a uniform UV intensity over an area remains challenging. Here, we propose a method to achieve a uniform areal intensity within an irradiated area by synchronizing the signal waveform and position of a UV-LED array. To verify our theoretical calculation, we developed a system with a UV-LED array whose position is controlled by a linear actuator. The intensity of the UV-LED array is controlled by a pulse width modulation (PWM) signal, which is synchronized with the position of the linear actuator. Using this system, we fabricated 2D micropatterns and 3D microstructures with high uniformity in the irradiated area. The proposed method is expected to facilitate practical LED-based lithography in MEMS fabrication. Published by AIP Publishing.

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Scalable fabrication of PEGDA microneedles using UV exposure via a rotating prism

H Takahashi, YJ Heo, I Shimoyama

Journal of Microelectromechanical Systems 26 (5), 990-992 (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC) 26 ( 5 ) 990 - 992 2017

Research paper (scientific journal), Joint Work, Accepted, ISSN 10577157

We propose a simple, fast, height-scalable, and direct way to fabricate highly biocompatible polyethylene glycol diacrylate (PEGDA) microneedles. A needle-shaped distribution of ultraviolet (UV) exposure dose is formed in PEGDA by applying UV light through a rotating prism. A prism makes UV light rays bend, such that the base angle of the prism determines the inclined angle of the light. Thus, the microneedle height can be controlled by varying the base angles of the prism. We experimentally demonstrate the direct height-scalable potential. The microneedle height decreases and the microneedle tip angle increases with increases in the base angle of the prism. These results indicate that the microneedle geometry can be easily controlled by the base angle of a prism without additional microfabrication. In addition, unlike photoresist microneedles, PEGDA does not require any thermal baking, thus enabling well-defined symmetric needle formation with short process time. Therefore, the present method can facilitate PEGDA microneedles to practical applications. [2017-0136]

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Pressure sensor having cantilever and displacement measurement unit

I Shimoyama, K Matsumoto, H Takahashi, MD Nguyen, Y Shinohara, ...

US Patent 9,551,621 2017

Pressure sensor

I Shimoyama, K Matsumoto, H Takahashi, MD Nguyen, T Uchiyama, ...

US Patent App. 15/512,701 2017

Pressure sensor

I Shimoyama, K Matsumoto, H Takahashi, MD Nguyen, T Uchiyama, ...

US Patent App. 15/116,967 2017

Evaluation of ground slippery condition during walk of bipedal robot using MEMS slip sensor

T Okatani, H Takahashi, T Takahata, I Shimoyama

2017 IEEE 30th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 1033 - 1035 2017

ISSN 9781509050789

© 2017 IEEE. This paper reports on a method to evaluate ground slippery condition using a MEMS slip sensor. The sensor discriminates between ground slippery and non-slippery conditions during walking motions of a bipedal robot, which enables the robot to prevent a slip. First, we evaluated the responses of the sensor pressed against an oiled or non-oiled surface. Then, we proposed a discriminating method between the oiled and non-oiled surfaces using the sensor. Finally, we demonstrated that a bipedal robot was able to evaluate the slippery condition of the ground where the foot of the robot landed during walk.

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Force Measurement by MEMS Sensors during Ant Running

H TAKAHASHI, I SHIMOYAMA

Journal of the Visualization Society of Japan 37 (144), 20-23 (可視化情報学会) 37 ( 144 ) 20 - 23,図巻頭1p 2017

ISSN 0916-4731

CiNii Research

Biomimetics and Visualization

H TANAKA, H TAKAHASHI

Journal of the Visualization Society of Japan 37 (144), 2-2 (The Visualization Society of Japan) 37 ( 144 ) 2 - 2 2017

ISSN 0916-4731

Gas sensor

I Shimoyama, K Matsumoto, KAN Tetsuo, Y Takei, H Takahashi, K Ishizu, ...

US Patent 9,546,948 2017

How merging droplets jump off a superhydrophobic surface: Measurements and model

T Mouterde, TV Nguyen, H Takahashi, C Clanet, I Shimoyama, D Quéré

Physical Review Fluids 2 (11), 112001 (AMER PHYSICAL SOC) 2 ( 11 ) 112001(R) 2017

Research paper (scientific journal), Joint Work, Accepted, ISSN 2469-990X

We investigate how drops merging on a nonwettable surface jump off this surface, for both symmetric and asymmetric coalescences. For this purpose, we design and build a microelectro mechanical system sensor able to quantify forces down to the micro-Newton scale at a high acquisition rate (200 kHz). Using this device, we perform direct force measurements of self-propelled droplets coupled to high-speed imaging. Experimental data show that the total momentum of the drop after coalescence mainly depends on the size of the smaller drop. Exploiting this finding, we quantitatively predict the takeoff speed of jumping drop pairs and show how to correct the usual argument based on energy conservation.

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Jumping force of coalescing droplets on a superhydrophobic surface

TV Nguyen, T Mouterde, H Takahashi, D Quéré, I Shimoyama

2017 IEEE 30th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 95 - 98 2017

ISSN 9781509050789

© 2017 IEEE. We report a method to directly measure the jumping force during the coalescence of two water droplets on a superhydrophobic surface using a MEMS-based force sensor as shown in Figure 1(a). The sensor is designed to measure the jumping force during the coalescence of two droplets whose radii are several hundred μm. The measurement results show that the maximum jumping force could be more than 10 times larger than the total weight of the merged droplet. Moreover, the impulse calculated from the measured force was on the same order with the jumping momentum of the droplet. Therefore, our sensor is a useful tool to investigate the mechanism of coalescence-induced droplet jumping.

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Maximum force capacity of legs of a fruit fly during landing motion

H Takahashi, R Furuya, T Yano, K Ito, T Takahata, I Shimoyama

2017 19th International Conference on Solid-State Sensors, Actuators and … (TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems) 1061 - 1064 2017

ISSN 9781538627310

© 2017 IEEE. This paper reports on measurement of landing force of a fruit fly (Drosophila melanogaster) using a MEMS force plate. By measuring the landing force of fruit flies, we found that the maximum force correlated with the landing velocity, which varied from several to 80 times larger than its weight. The experimental result suggested that there was the threshold value of the maximum landing force per weight for legs, which determined that a fruit fly lands with contacting with six legs or colliding bodily to the ground according to the landing velocity. The threshold value was thought to be the maximum force capacity of legs during landing motion.

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Mems force and displacement sensor for measuring spring constant of hydrogel microparticles

S Kohyama, H Takahashi, S Yoshida, H Onoe, KH Shoji, T Tsukagoshi, ...

2017 IEEE 30th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 1040 - 1043 2017

ISSN 9781509050789

© 2017 IEEE. This paper reports on a method to measure spring constant of hydrogel microparticles by a MEMS sensor. For calculating spring constant, not only force but also displacement is necessary. The MEMS sensor consists of two sidewall doped piezoresistive cantilevers in the ranges of μΝ and μm so that both parameters can be measured simultaneously. When one cantilever pushes a target to a wall, the cantilever can measure the restoring force of the target. At the same time, the other cantilever measures the displacement by pushing the wall directly. By measuring both force and displacement on the same sensor chip, the spring constant of targets can be obtained only from the sensor outputs, which makes the sensor system simple and compact. With this advantage, our method can be useful in actual experiments with microscopes and other systems.

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Ornithopter with a MEMS Differential Pressure Sensor

Takahashi Hidetoshi, Shimoyama Isao

Journal of the Robotics Society of Japan (The Robotics Society of Japan) 35 ( 9 ) 660 - 663 2017

Flight Force Measurement of Fruit Flies under Steady Airflow

HAGIWARA Takehiro, TAKAHASHI Hidetoshi, YANO Tomoko, ITO Kei, TAKAHATA Tomoyuki, SHIMOYAMA Isao

The Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) (The Japan Society of Mechanical Engineers) 2017 1A1 - J11 2017

We measured the flight force of fruit flies under the steady airflow. To measure the flight force, we used a MEMS triaxial force sensor. A fruit fly was glued to a sensor with UV curable resin. A wind tunnel was made to apply the steady airflow. The wind tunnel consisted of a flow straightening section, a contract section, a test section and fans. The size of the test section where the sensor was attached to was 50 mm × 50 mm × 150 mm. We measured the flight force at the velocity of airflow 0 m/s, 1.6 m/s and 2.2 m/s. Simultaneously, we took high-speed videos of the flapping of wings. The result suggested that the faster the airflow velocity was, the lower the force of flying forward was. The trajectory of wings also changed in accordance with the velocity of the airflow.

Measurement of the Effect of Fixed Wing on Flapping Flight

ABE Kosuke, TAKAHASHI Hidetoshi, TAKAHATA Tomoyuki, SHIMOYAMA Isao

The Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) (The Japan Society of Mechanical Engineers) 2017 2A1 - M03 2017

In this paper, we evaluated the effect of fixed wings of a beetle-inspired ornithopter during flapping flight. The fixed wings of the fabricated beetle-inspired ornithopter were attachable to either the leading or tailing side of the flapping wings. MEMS differential pressure sensors were attached to both fixed and flapping wings surfaces to evaluate the aerodynamic performance of the wings. We performed flight experiments with 3 types of ornithopter; fixed wings in leading side of the flapping wings, fixed wings tailing side the flapping wings, without fixed wings. The result suggested the fixed wings of the leading side enhanced lift force and stabilized pitching comparing with the other types during flapping flight.

Measurement of vacuum pressure with cantilever-based differential pressure sensor utilizing vapor pressure and narrow gap of cantilever

N Namioka, Y Takei, N Minh-Dung, T Usami, N Thanh-Vinh, H Takahashi, ...

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2016-February 836 - 838 2016

ISSN 9781509019731

© 2016 IEEE. This paper reports a measurement method of vacuum pressure from 10-1 to 103 Pa with a piezoresistive cantilever-based differential pressure sensor (DPS). The gap around the cantilever of the DPS was narrow (2 μm) so that the air flow through it was suppressed. The through-hole beneath the sensor is connected to a chamber which is filled with saturated vapor. This method allows the pressure of the chamber to be stable at the vapor pressure of the liquid even when the exterior was vacuumed. The exterior vacuum pressure was calculated from the cantilever output since the vapor pressure of the chamber is known. We showed that the lower limit of measurable range was expanded into 0.1 Pa owing to noise reduction. The proposed method is promising to realize wide-range vacuum pressure measurement.

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Depinning-induced capillary wave during the sliding of a droplet on a textured surface

TV Nguyen, T Tsukagoshi, H Takahashi, K Matsumoto, I Shimoyama

Langmuir 32 (37), 9523-9529 (AMER CHEMICAL SOC) 32 ( 37 ) 9523 - 9529 2016

Research paper (scientific journal), Joint Work, Accepted, ISSN 07437463

Surfaces covered with hydrophobic micro-/nanoscale textures can allow water droplets to slide easily because of low contact angle hysteresis. In contrast to the case of a droplet sliding on a smooth surface, when a droplet slides on a textured surface, it must recede from the textures at its rear edge and the resultant depinning events induce a capillary wave on the surface of the droplet. Although this depinning-induced capillary wave can be observed to some extent through high-speed imaging, important parameters of the wave, such as the wavelength and frequency, and the factors that determine these parameters are not fully understood. We report direct measurements of this depinning-induced capillary wave using microelectromechanical systems (MEMS)-based force sensors fabricated on a textured surface. Such sensor measurements reveal the frequency of the vibration occurring on the surface of the droplet, from which it is possible to calculate the wavelength of the capillary wave. We show that the frequency and wavelength, of the depinning-induced capillary wave during the sliding of a water droplet on a micropillar array depend upon, neither the size of the droplet nor its sliding velocity. However, the frequency (wavelength) decreases (increases) as the pitch of the micropillar array increases. We argue that the wavelength of the depinning-induced capillary wave is equal to. the maximum length of:the liquid bridges that develop at the micropillars before depinning. This hypothesis is confirmed by comparing,the wavelengths obtained from the sensor measurements to the maximum liquid-bridge lengths calculated from observations using a high-speed camera.

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Chiral switchable THz metamaterial with MEMS reconfigurable spirals

T Kan, A Isozaki, N Kanda, N Nemoto, K Konishi, H Takahashi, ...

CLEO: QELS_Fundamental Science, FTh3D. 8 (2016 Conference on Lasers and Electro-Optics, CLEO 2016) 2016

ISSN 9781943580118

Cantilever with 10-fold tunable spring constant using Lorentz force

W Ohnishi, H Takahashi, T Takahata, K Matsumoto, I Shimoyama

ISSN 9781509019731

© 2016 IEEE. This paper reports a cantilever with 10-fold tunable spring constant. The spring constant can be tuned both larger and smaller using Lorentz force generated by direct current which flows through the wiring on the cantilever. We designed the cantilever so that the maximum spring constant change by Lorentz force can be the same order as initial spring constant. The change of the spring constant was evaluated from the resonant frequency shift. The experimental result shows that the resonant frequency can be controlled from 1.1 kHz to 3.8 kHz, and the ratio of the tuned spring constant to the initial value was evaluated to be from 0.22 to 2.6.

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A tactile sensor using piezoresistive beams for detection of the coefficient of static friction

T Okatani, H Takahashi, K Noda, T Takahata, K Matsumoto, I Shimoyama

Sensors 16 (5), 718 (MDPI AG) 16 ( 5 ) 718 2016

Research paper (scientific journal), Joint Work, Accepted, ISSN 14248220

This paper reports on a tactile sensor using piezoresistive beams for detection of the coefficient of static friction merely by pressing the sensor against an object. The sensor chip is composed of three pairs of piezoresistive beams arranged in parallel and embedded in an elastomer; this sensor is able to measure the vertical and lateral strains of the elastomer. The coefficient of static friction is estimated from the ratio of the fractional resistance changes corresponding to the sensing elements of vertical and lateral strains when the sensor is in contact with an object surface. We applied a normal force on the sensor surface through objects with coefficients of static friction ranging from 0.2 to 1.1. The fractional resistance changes corresponding to vertical and lateral strains were proportional to the applied force. Furthermore, the relationship between these responses changed according to the coefficients of static friction. The experimental result indicated the proposed sensor could determine the coefficient of static friction before a global slip occurs.

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A tactile sensor for simultaneous measurement of applied forces and friction coefficient

T Okatani, H Takahashi, K Noda, T Takahata, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2016 IEEE 29th International … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 2016-February 862 - 865 2016

ISSN 9781509019731

© 2016 IEEE. This paper reports on a tactile sensor to measure normal force, tangential force and friction coefficient simultaneously. The proposed sensor is composed of three pairs of piezoresistive beams embedded in an elastomer. The normal and tangential forces can be measured by detecting the normal and shear deformations of the elastomer with the piezoresistive beams. The friction coefficient can be measured by calculating the ratio of the extension of the elastomer to the normal force. We demonstrated that the normal force from 0 to 8 N and the tangential force from 0 to 0.8 N were able to be measured independently by using the fabricated sensor. Moreover, we found that the ratio of the outputs from the piezoresistors was independent of the applied forces, and varied with the coefficients of static friction from 0.2 to 1.5.

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The sound of a sliding droplet

N Thanh-Vinh, H Takahashi, T Tsukagoshi, K Matsumoto, I Shimoyama

ISSN 9781509019731

© 2016 IEEE. In this paper, we report on a direct measurement of the vibration on the surface of a droplet during its sliding on a micropillar array. The measurement is realized by using a MEMS-based force sensor fabricated under a micropillar. Our method provides direct information on the frequency of the vibration which was difficult to be obtained by conventional observation-based methods. We demonstrate that in case of a water droplet sliding on a 125 μm-pitch micropillar array, a vibration at frequency of approximately 3 kHz was found to occur on the droplet surface. Moreover, we show that the frequency of the vibration during the sliding of a droplet on a micropillar array does not depend on the sliding velocity nor the volume of the droplet.

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The effect of the phase angle between the forewing and hindwing on the aerodynamic performance of a dragonfly-type ornithopter

H Takahashi, A Concordel, J Paik, I Shimoyama

Aerospace 3 (1), 4 (Aerospace) 3 ( 1 ) 4 2016

Joint Work, Accepted

© 2016 by the authors. Dragonflies achieve agile maneuverability by flapping four wings independently. Different phase angles between the flapping forewing and hindwing have been observed during various flight modes. The aerodynamic performance depends on phase angle control, as exemplified by an artificial flying ornithopter. Here, we present a dragonfly-like ornithopter whose phase angle was designed to vary according to the phase lag between the slider-cranks of the forewing and hindwing. Two microelectromechanical systems (MEMS) differential pressure sensors were attached to the center of both forewing and hindwing to evaluate the aerodynamic performance during flapping motions when the phase angle was changed. By varying the phase angle in both the tethered condition and free-flight, the performance of the forewing remained approximately constant, whereas that of the hindwing exhibited obvious variations; the maximum average value was two-fold higher than the minimum. The experimental results suggest that simple phase angle changes enable a flying ornithopter to control flight force balance without complex changes in the wing kinematics.

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Tactile sensor and multi-axial tactile sensor

I Shimoyama, K Matsumoto, A Nakai, H Takahashi

US Patent 9,310,265 2016

Sensitivity enhancement of a cantilever-type airflow shear stress sensor via surface roughness modification

R Kazama, H Takahashi, N Thanh-Vinh, T Takahata, K Matsumoto, ...

ISSN 9781509019731

© 2016 IEEE. This paper reports an airflow shear stress sensor whose sensitivity is enhanced by modifying the surface roughness. The sensor consists of a cantilever-typed shear stress sensor and a micro pillar array on the surface of the cantilever. Piezoresistors are formed on the side walls of the cantilever's hinges to detect the shear force acting on the cantilever. When a shear airflow is applied to the proposed sensor, the shear force is generated on the surface of not only the cantilever but also the micro pillar array. Therefore, for the same airflow velocity, the total shear force acting on the surface of the proposed sensor is larger than that acting on the surface of a sensor with a flat surface. The experimental results show that the micro pillar structure improves the sensor sensitivity in response to airflow by 5 times compared with the flat surface structure.

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Scalable fabrication of microneedle arrays via spatially controlled UV exposure

H Takahashi, YJ Heo, N Arakawa, T Kan, K Matsumoto, R Kawano, ...

Microsystems & nanoengineering 2, 16049 (NATURE PUBLISHING GROUP) 2 16049 2016

Research paper (scientific journal), Joint Work, Accepted, ISSN 2055-7434

This paper describes a theoretical estimation of the geometry of negative epoxy-resist microneedles prepared via inclined/rotated ultraviolet (UV) lithography based on spatially controlled UV exposure doses. In comparison with other methods based on UV lithography, the present method can create microneedle structures with high scalability. When negative photoresist is exposed to inclined/rotated UV through circular mask patterns, a three-dimensional, needle-shaped distribution of the exposure dose forms in the irradiated region. Controlling the inclination angles and the exposure dose modifies the photo-polymerized portion of the photoresist, thus allowing the variation of the heights and contours of microneedles formed by using the same mask patterns. In an experimental study, the dimensions of the fabricated needles agreed well with the theoretical predictions for varying inclination angles and exposure doses. These results demonstrate that our theoretical approach can provide a simple route for fabricating microneedles with on-demand geometry. The fabricated microneedles can be used as solid microneedles or as a mold master for dissolving microneedles, thus simplifying the microneedle fabrication process. We envision that this method can improve fabrication accuracy and reduce fabrication cost and time, thereby facilitating the practical applications of microneedle-based drug delivery technology.

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Rigid two-axis MEMS force plate for measuring cellular traction force

H Takahashi, UG Jung, T Kan, T Tsukagoshi, K Matsumoto, I Shimoyama

Journal of Micromechanics and Microengineering 26 (10), 105006 (IOP PUBLISHING LTD) 26 ( 10 ) 105006 2016

Research paper (scientific journal), Joint Work, Accepted, ISSN 09601317

Cellular traction force is one of the important factors for understanding cell behaviors, such as spreading, migration and differentiation. Cells are known to change their behavior according to the mechanical stiffness of the environment. However, the measurement of cell traction forces on a rigid environment has remained difficult. This paper reports a micro-electromechanical systems (MEMS) force plate that provides a cellular traction force measurement on a rigid substrate. Both the high force sensitivity and high stiffness of the substrate were obtained using piezoresistive sensing elements. The proposed force plate consists of a 70 mu m x 15 mu m x 5 mu m base as the substrate for cultivating a bovine aortic smooth muscle cell, and the supporting beams with piezoresistors on the sidewall and the surface were used to measure the forces in both the horizontal and vertical directions. The spring constant and force resolution of the fabricated force plate in the horizontal direction were 0.2 N m(-1) and less than 0.05 mu N, respectively. The cell traction force was measured, and the traction force increased by approximately 1 mu N over 30 min. These results demonstrate that the proposed force plate is applicable as an effective traction force measurement.

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Pressure sensor

I Shimoyama, K Matsumoto, H Takahashi, MD Nguyen, T Uchiyama, ...

US Patent App. 15/117,272 2016

Evaluation of insect locomotion using MEMS piezoresistive force sensors

H Takahashi, I Shimoyama

2016 IEEE 16th International Conference on Nanotechnology (IEEE-NANO), 931-932 (16th International Conference on Nanotechnology - IEEE NANO 2016) 931 - 932 2016

ISSN 9781509039142

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Gas sensor

I Shimoyama, K Matsumoto, Y Takei, H Takahashi, N Kiga, M Honda

US Patent 9,250,210 2016

Measurement of jumping force of a fruit fly using a mesa structured force plate

R Furuya, H Takahashi, NT Vinh, T Yano, K Ito, T Takahata, K Matsumoto, ...

ISSN 9781509019731

© 2016 IEEE. This paper reports on a mesa structured force plate for measurement of jumping force of a fruit fly. The proposed force plate is 5 mm × 5 mm × 20 μm in size. The thickness of the sensing beams is 7.5 μm which is thinner than that of the plate to increase the sensitivity in response to normal force. Using the fabricated force plate, the jumping force of a fruit fly was measured when it took off from the plate surface. The measurement result shows that the maximum value of the jumping force is approximately 8 times larger than the weight (mG, where m and G are the fruit fly mass and gravitational acceleration) of a fruit fly.

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Quantitative correlation between cardiac MIBG uptake and remaining axons in the cardiac sympathetic nerve in Lewy body disease

Takahashi M., Ikemura M., Oka T., Uchihara T., Wakabayashi K., Kakita A., Takahashi H., Yoshida M., Toru S., Kobayashi T., Orimo S.

Journal of Neurology, Neurosurgery and Psychiatry (Journal of Neurology, Neurosurgery and Psychiatry) 86 ( 9 ) 939 - 944 2015.09

ISSN 00223050

Objectives Reduced cardiac meta-iodobenzylguanidine (MIBG) uptake and loss of cardiac sympathetic axons, as its possible anatomical substrate, were both recognised in Lewy body disease (LBD), while their direct correlation has so far remained speculative. Increasing availability of autopsy-confirmed cases of LBD prompted us to quantify residual cardiac sympathetic axons to establish their relationship to cardiac MIBG uptake. Methods We collected cardiac tissue samples from 23 patients with autopsy-confirmed LBD and two non-LBD control patients who underwent 123 I-MIBG cardiac scintigraphy in life. Samples of the left ventricular anterior wall were stained with anti-tyrosine hydroxylase (TH) and anti-neurofilament (NF) antibodies as markers of cardiac nerve axons. We quantified the immunolabelled areas and assessed their correlation to standardised heart to mediastinum (H/M) ratios of 123 I-MIBG cardiac scintigraphy. Results Cardiac MIBG uptake in the early and delayed phases was reduced in 90.9% and 95.7% of patients with LBD, respectively. The area of TH-immunoreactive axons correlated significantly with the H/M ratio in the early (p=0.036) as well as in the delayed (p=0.018) phases. The area of NF-immunoreactive axons also correlated with the H/M ratio in the early (p=0.003) as well as in the delayed (p=0.001) phases. Conclusions Tight quantitative correlation between cardiac 123 I-MIBG uptake and corresponding loss of sympathetic axons in LBD, as established for the first time by this study, provides a scientific basis to confirm the reliability of MIBG cardiac scintigraphy as a powerful clinical tool to detect loss of these axons as a biomarker for the presence of Lewy body disease.

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Analysis of MEMS Spiral Metamaterial in the THz frequency

Kan Tetsuo, Isozaki Akihiro, Kanda Natsuki, Nemoto Natsuki, Konishi Kuniaki, Kuwata-Gonokami Makoto, Matsumoto Kiyoshi, Shimoyama Isao

JSAP Annual Meetings Extended Abstracts (The Japan Society of Applied Physics) 2015.1 862 - 862 2015.02

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Microneedle array fabrication using inclined/rotated uv lithography

Heo Y., Arakawa N., Yoshizawa S., Takahashi H., Kawano R.

MicroTAS 2015 - 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS 2015 - 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences) 1442 - 1444 2015

ISSN 9780979806483

Insects have hairy eyes that reduce particle deposition

GJ Amador, F Durand, W Mao, S Pusulri, H Takahashi, VT Nguyen, ...

The European Physical Journal Special Topics 224 (17-18), 3361-3377 (SPRINGER HEIDELBERG) 224 ( 17-18 ) 3361 - 3377 2015

Research paper (scientific journal), Joint Work, Accepted, ISSN 19516355

An insect's eyes may make up to 40% of its body's surface, and are in danger of being coated by foreign particles such as dust and pollen. To protect them, several insect species possess an array of ocular hairs evenly spaced between each photoreceptor unit. Although these hairs have been observed for over 50 years, their purpose remains a mystery. In this study, we elucidate the function of ocular hairs using a combination of experiments, numerical simulation and micro-fabrication. We measure the eyes of 18 species of insects and find that the length of their ocular hairs is equal to their spacing. We conduct wind tunnel experiments using both an insect eye mimic and an at-scale fabricated micro-pillar array of the same dimensions as the insect eye. Our experiments and simulations show that ocular hairs reduce airflow at the eye surface by up to 90%. We conclude that ocular hairs act similarly to mammalian eyelashes: as insects fly, ocular hairs deflect incoming air and create a zone of stagnant air. Airflow and particle deposition are reduced dramatically, while light is only minimally occluded. Micro-scale ocular hairs may find application in the deployment of sensors outdoors, for which accumulation of airborne dust and pollen has no current solution.

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Differential pressure sensor

I Shimoyama, K Matsumoto, T Takahata, KAN Tetsuo, K Kuwana, ...

US Patent 9,188,497 2015

Airflow shear stress sensor using side-wall doped piezoresistive plate

R Kazama, H Takahashi, T Takahata, K Matsumoto, I Shimoyama

2015 28th IEEE International Conference on Micro Electro Mechanical Systems … (IEEE) 2015-February ( February ) 710 - 713 2015

ISSN 10846999

This paper reports on a shear stress sensor for airflow. The sensor consists of a plate, side-wall doped beams and surrounding membrane with narrow gaps. The sensor plate was 300 mu mx350 mu mx3 um in size. The plate was supported by the side-wall doped beams, which can detect their horizontal deformation. The sensor structure was designed not to disturb target airflow circumstance owing to its flat surface. The fabricated sensor was able to measure shear stress of laminar airflow with the resolution under 1.0 Pa.

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A cantilever with comb structure modeled by a bristled wing of thrips for slight air leak

H Takahashi, A Isozaki, K Matsumoto, I Shimoyama

2015 28th IEEE International Conference on Micro Electro Mechanical Systems … (IEEE) 2015-February ( February ) 706 - 709 2015

ISSN 10846999

This paper reports a cantilever with comb structure, inspired by a bristled wing of thrips which acts as a continuous membrane wing because of the effects of low Reynolds numbers. The comb structures are formed at the edges of the cantilever and its surrounding frame. When differential pressure is applied to the cantilever, both comb structures act as airflow suppression through the gap. The leakage of the fabricated comb cantilever was smaller than the normal cantilever due to the overlapping area of the combs, even the gap area was twice larger. The proposed structure will be utilized as a high sensitive barometric pressure change detector.

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6-Axis force/torque sensor for spike pins of sports shoes

H Ishido, H Takahashi, A Nakai, T Takahata, K Matsumoto, I Shimoyama

2015 28th IEEE International Conference on Micro Electro Mechanical Systems … (IEEE) 2015-February ( February ) 257 - 260 2015

ISSN 10846999

This paper reports on a method to measure forces and torques acting on spike pins of sports shoes. We fabricated a 2 mm x 2 mm x 0.3 mm 6-axis force/torque sensor chip, which consists of 6 piezoresistive beams. From the resistance changes of the 6 beams, 6 components of forces and torques can be detected. The sensor chip was connected to a flexible printed circuit board (PCB) and covered with thin polydimethylsiloxane (PDMS). Then, the sensor chip and flexible PCB were embedded in spike-pin-shaped epoxy resin. We calibrated the spike-pin-shaped sensor, and confirmed that 6-axis forces and torques were able to be detected by the proposed sensor.

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3D structural foramation utilizing glass transition of a Parylene film

T Kan, A Isozaki, H Takahashi, K Matsumoto, I Shimoyama

2015 28th IEEE International Conference on Micro Electro Mechanical Systems … (IEEE) 2015-February ( February ) 405 - 408 2015

ISSN 10846999

This paper reports on a fabrication method of three-dimensional micro structures supported by a Parylene thin film. The three-dimensional structure formation procedure starts with an out-of-plane actuation of the Si surface micromachined structure coated with a thin Parylene film. At the same time of the actuation, the environmental temperature was elevated above the glass transition temperature T-g of the Parylene, 80-100 degrees C, and then cooled down below T-g. In this process, the rearrangement of the Parylene film happens above T-g, and the consolidated Parylene after the cooling down maintains three-dimensional micro structures as actuated. In a proof-of-principle experiment, the three-dimensional spiral structures formed by 300-nm-thick silicon were fixed by 1-mu m-thick Parylene film.

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Viscosity measurement based on the tapping-induced free vibration of sessile droplets using MEMS-based piezoresistive cantilevers

TV Nguyen, MD Nguyen, H Takahashi, K Matsumoto, I Shimoyama

Lab on a Chip 15 (18), 3670-3676 (ROYAL SOC CHEMISTRY) 15 ( 18 ) 3670 - 3676 2015

Joint Work, Accepted, ISSN 14730197

We report a simple technique to measure the free vibration of microlitre-sized droplets using an array of thirteen MEMS-based piezoresistive cantilevers and demonstrate its application for the measurement of viscosity. Because the damping of the free vibration of a liquid droplet is known to be affected by the viscosity of the liquid, measuring the vibration of a droplet allows the viscosity to be estimated from a dilute sample volume. However, conventional methods to measure the droplet vibration require sophisticated apparatuses, which hinder the development of a portable viscometer. Here, we show that MEMS-based piezoresistive cantilevers can be an excellent tool to measure the vibration of a sessile droplet due to the high sensitivity and simplicity of the readout scheme. Using the cantilever array, we analyse the normal force distribution on the contact area of a sessile droplet in the static state and during the vibration. Next, we show that the viscosity (from similar to 1-30 mPa s) can be estimated within an error of less than 10% from the attenuation rate of the cantilever output during the tapping-induced vibration of small droplets (similar to 2.4 mu L). In addition to the advantage of the small sample volume, the proposed viscometer has simple operation and readout schemes, which are desirable for many applications, including point-of-care testing and drug development.

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Two-axis MEMS-based force sensor for measuring the interaction forces during the sliding of a droplet on a micropillar array

N Thanh-Vinh, H Takahashi, K Matsumoto, I Shimoyama

Sensors and Actuators A: Physical 231, 35-43 (ELSEVIER SCIENCE SA) 231 35 - 43 2015

Joint Work, Accepted, ISSN 09244247

In this paper, we proposed a 2-axis MEMS-based force sensor to directly measure the interaction forces during the sliding of a water droplet on a superhydrophobic surface with a micropillar array. In our sensor design, a 300-nm-thick silicon (Si) structure was fabricated beneath a single micrometer-sized pillar as the sensing element. Two piezoresistors were formed at the root of two opposite Si beams to detect the forces acting on the pillar surface in the normal and shear directions. The proposed sensor has a sensing resolution of less than 20 nN for both normal and shear forces. This resolution is confirmed to be sufficient to measure the forces of a droplet acting on a micropillar. The fabricated sensor was demonstrated to be able to measure the interaction forces during the sliding of a 7.5 mu L water droplet on the micropillar array. (C) 2014 Elsevier B.V. All rights reserved.

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Quad-axial piezoresistive force sensor probe by four sensing elements with sidewall doping method

H Takahashi, S Hirakawa, T Takahata, K Matsumoto, I Shimoyama

2015 Transducers-2015 18th International Conference on Solid-State Sensors … (2015 Transducers - 2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS 2015) 1089 - 1092 2015

ISSN 9781479989553

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Out-of-plane actuation with a sub-micron initial gap for reconfigurable terahertz micro-electro-mechanical systems metamaterials

A Isozaki, T Kan, H Takahashi, K Matsumoto, I Shimoyama

Optics express 23 (20), 26243-26251 (OPTICAL SOC AMER) 23 ( 20 ) 26243 - 26251 2015

Joint Work, Accepted, ISSN 1094-4087

We propose a reconfigurable terahertz (THz) metamaterial that can control the transmittance by out-of-plane actuation with changing the sub-micron gap distance between electrically coupled metamaterial elements. By using the out-of-plane actuation, it was possible to avoid contact between the coupled metamaterial elements across the small initial gap during the adjustment of the gap size. THz spectroscopy was performed during actuation, and the transmission dip frequency was confirmed to be tunable from 0.82 to 0.92 THz for one linear polarization state and from 0.80 to 0.91 THz for the other linear polarization; the two polarizations were orthogonal. The proposed approach will contribute to the development of tunable metamaterials based on structural deformations. (C) 2015 Optical Society of America

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Enantiomeric switching of chiral metamaterial for terahertz polarization modulation employing vertically deformable MEMS spirals

T Kan, A Isozaki, N Kanda, N Nemoto, K Konishi, H Takahashi, ...

Nature communications 6, 8422 (NATURE PUBLISHING GROUP) 6 8422 2015

Joint Work, Accepted, ISSN 2041-1723

Active modulation of the polarization states of terahertz light is indispensable for polarization-sensitive spectroscopy, having important applications such as non-contact Hall measurements, vibrational circular dichroism measurements and anisotropy imaging. In the terahertz region, the lack of a polarization modulator similar to a photoelastic modulator in the visible range hampers expansion of such spectroscopy. A terahertz chiral metamaterial has a huge optical activity unavailable in nature; nevertheless, its modulation is still challenging. Here we demonstrate a handedness-switchable chiral metamaterial for polarization modulation employing vertically deformable Micro Electro Mechanical Systems. Vertical deformation of a planar spiral by a pneumatic force creates a three-dimensional spiral. Enantiomeric switching is realized by selecting the deformation direction, where the polarity of the optical activity is altered while maintaining the spectral shape. A polarization rotation as high as 28 degrees is experimentally observed, thus providing a practical and compact polarization modulator for the terahertz range.

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Characteristic evaluation of a bristled wing using mechanical models of a thrips wings with MEMS piezoresistive cantilevers

H TAKAHASHI, K SATO, MD NGUYEN, K MATSUMOTO, I SHIMOYAMA

Journal of Biomechanical Science and Engineering 10 (2), 14-00233-14-00233 (Japan Society of Mechanical Engineers) 10 ( 2 ) 1 - 10 2015

Joint Work, Accepted, ISSN 18809863

This paper discusses similar-scale mechanical models of a thrips wing using microelectromechanical systems (MEMS) piezoresistive cantilevers to quantitatively evaluate bristled wing characteristics. Each cantilever had combs with varying widths and neighboring gaps that were adjusted so that a constant surface area was maintained. The cantilever body was 1,324 × 256 × 5 μm&lt
sup&gt
3&lt
/sup&gt
in size. An aerodynamic drag force from the airflow applied to the cantilever surface was measured using the fractional resistance change of the piezoresistor due to the cantilever's deformation. The aerodynamic characteristics of each model were evaluated in a wind tunnel with airflow velocities between 1.2 and 5.6 m/s. The experimental results suggest that at a lower comb-width-based Reynolds number that was approximately equal to that of a bristled wing of a thrips, the comb areas of the cantilever act as an airflow suppression due to boundary layer effects, which results in an increased aerodynamic force.

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Fusion of cantilever and diaphragm pressure sensors according to frequency characteristics

R Watanabe, N Minh-Dung, H Takahashi, T Takahata, K Matsumoto, ...

2015 28th IEEE International Conference on Micro Electro Mechanical Systems … (IEEE) 2015-February ( February ) 212 - 214 2015

ISSN 10846999

This paper reports on an approach to measure sensitive barometric pressure by fusing a cantilever-based differential pressure sensor (DPS) and a commercially available diaphragm-based absolute pressure sensor (APS). At high frequency, the DPS can detect smaller pressure change than the APS. At low frequency, the APS shows less drift absolute pressure than the DPS. By utilizing the DPS and APS at each advantageous frequency, we propose a highly sensitive and drift-free measurement of barometric pressure.

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MEMS Force Sensor for Study of Droplet Sliding

TV NGUYEN, H TAKAHASHI, K MATSUMOTO, I SHIMOYAMA

電気学会フィジカルセンサ研究会資料, 47-51 PHS-15 ( 31-43 ) 47 - 51 2015

Parallel Helmholtz resonators for a planar acoustic notch filter

A Isozaki, H Takahashi, H Tamura, T Takahata, K Matsumoto, ...

Applied Physics Letters 105 (24), 241907 (AMER INST PHYSICS) 105 ( 24 ) 241907 2014

Joint Work, Accepted, ISSN 00036951

This paper reports on an acoustic planar notch filter with a sub-wavelength thickness at the notch frequency. The developed notch filter consists of a number of spherical Helmholtz resonators (HRs) connected to a hole created in a plate. The HRs were placed at the in-plane vertices of a regular polygon. A simulated pressure distribution revealed that this uniform arrangement of HRs improves the silencing effect because the uniform applied waves emitted from the HRs act as canceling waves to the cross-section of the short hole (in this case, the length of the hole is sub-wavelength). The total pressure emitted from the HRs is equal regardless of the number of HRs connected to the hole. Therefore, the arrangement of HRs is essential for realizing a planar notch filter. Simulated transmittance spectra showed that the depth of the dip in the transmittance increased with the number of uniformly arranged HRs. We confirmed that the experimental transmittance spectra of fabricated notch filters, which consisted of between one and six HRs, agreed with the simulated transmittance spectra. The design of the acoustic filter presented in this study and the corresponding analysis should motivate further development of thin acoustic filters. (C) 2014 AIP Publishing LLC.

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MEMS two-axis force plate array used to measure the ground reaction forces during the running motion of an ant

H Takahashi, N Thanh-Vinh, UG Jung, K Matsumoto, I Shimoyama

Journal of Micromechanics and Microengineering 24 (6), 065014 (IOP PUBLISHING LTD) 24 ( 6 ) 065014 2014

Joint Work, Accepted, ISSN 09601317

A terrestrial insect can perform agile running maneuvers. However, the balance of ground reaction forces (GRFs) between each leg in an insect have remained poorly characterized. In this report, we present a micro force plate array for the simultaneous measurement of the anterior and vertical components of GRFs of multiple legs during the running motion of an ant. The proposed force plate, which consists of a 2000 mu m x 980 mu m x 20 mu m plate base as the contact surface of an ant's leg, and the supported beams with piezoresistors on the sidewall and surface are sufficiently compact to be adjacently arrayed along the anterior direction. Eight plates arrayed in parallel were fabricated on the same silicon-on-insulator substrate to narrow the gap between each plate to 20 mu m. We compartmented the plate surface into 32 blocks and evaluated the sensitivities to two-axis forces in each block so that the exerted forces could be detected wherever a leg came into contact. The force resolutions in both directions were under 1 mu N within +/- 20 mu N. Using the fabricated force plate array, we achieved a simultaneous measurement of the GRFs of three legs on one side while an ant was running.

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Direct measurement of the interaction forces during the sliding of a water droplet on a pillar-typed superhydrophobic surface

TV Nguyen, H Takahashi, K Matsumoto, I Shimoyama

APS Meeting Abstracts 2014

A smart, intermittent driven particle sensor with an airflow change trigger using a lead zirconate titanate (PZT) cantilever

H Takahashi, Y Tomimatsu, T Kobayashi, A Isozaki, T Itoh, R Maeda, ...

Measurement Science and Technology 25 (2), 025103 (IOP PUBLISHING LTD) 25 ( 2 ) 025103 2014

Research paper (scientific journal), Joint Work, Accepted, ISSN 09570233

This paper reports on a smart, intermittent driven particle sensor with an airflow trigger. A lead zirconate titanate cantilever functions as the trigger, which detects an airflow change without requiring a power supply to drive the sensing element. Because an airflow change indicates that the particle concentration has changed, the trigger switches the optical particle counter from sleep mode to active mode only when the particle concentration surrounding the sensor changes. The sensor power consumption in sleep mode is 100 times less than that in the active mode. Thus, this intermittent driven method significantly reduces the total power consumption of the particle sensor. In this paper, we fabricate a prototype of the particle sensor and demonstrate that the optical particle counter can be switched on by the fabricated trigger and thus that the particle concentration can be measured.

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Tunable metamaterials by controlling sub-micron gap for the THz range

A Isozaki, T Kan, H Takahashi, N Kanda, N Nemoto, K Konishi, ...

2014 IEEE 27th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 1221 - 1224 2014

ISSN 9781479935086

We propose a tunable metamaterial actuated by pneumatic force. The unit of the proposed metamaterial has a pair of sprit-ring-resonators (SRR), and the gap between them is controllable around sub-micron-order in size. One SRR is formed on a thin cantilever, which can be bent due to differential pressure between the upper and lower surfaces of the cantilever, whereas the other is fixed on a thin membrane. We confirmed that controlling the gap ranging from sub-micron-order to a few-micron-order was suitable for tuning a resonant frequency of a terahertz metamaterial. © 2014 IEEE.

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Traction force of smooth muscle cell during growth on a rigid substrate

UG Jung, T Tsukagoshi, H Takahashi, T Kan, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2014 IEEE 27th International … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 290 - 293 2014

ISSN 9781479935086

This paper reports on the sensor for traction force measurement of a smooth muscle cell during cell growth on a rigid substrate, specially designed for horizontal and vertical directional forces. For quantitative measurement, the cells are cultured only on the sensor pads using a cover chip. The length of the sensor is 1130μm. The size of the sensor pad is 125μm×15μ m×5μm (length×width× thickness). The gaps between the sensor pads are 3μm. We confirmed that the cells spread on the two sensor pads at least. We measured the traction forces of bovine aortic smooth muscle cells (BAOSMCs, CAB35405) using the proposed sensor. When the three cells spread on the pads, the measured traction forces in x and z direction increased 30nN and 20nN for 8 min, respectively. © 2014 IEEE.

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High-sensitivity triaxial tactile sensor with elastic microstructures pressing on piezoresistive cantilevers

N Thanh-Vinh, N Binh-Khiem, H Takahashi, K Matsumoto, I Shimoyama

Sensors and Actuators A: Physical 215, 167-175 (ELSEVIER SCIENCE SA) 215 167 - 175 2014

Joint Work, Accepted, ISSN 09244247

In this paper, we proposed a design to increase the sensitivity of a piezoresistive-type triaxial tactile sensor. Using conventional piezoresistive tactile sensors, in which the piezoresistive elements were completely embedded inside an elastic block, our proposed tactile sensor design features an air cavity underneath the piezoresistive elements. The cavity was created by pressing an elastic cap with microstructures onto the piezoresistive cantilevers of a sensor chip. We confirmed that the proposed design increased the sensitivity of the tactile sensor by approximately 150 times and 100 times in response to normal and lateral forces, respectively. (C) 2013 Elsevier B.V. All rights reserved.

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Interaction forces during the sliding of a water droplet on a textured surface

N Thanh-Vinh, H Takahashi, K Matsumoto, I Shimoyama

2014 IEEE 27th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 979 - 982 2014

ISSN 9781479935086

We have directly measured the interaction forces (in normal and lateral directions) during the sliding of a water droplet on a surface decorated with a micropillar array. The measurement was carried out using a MEMS-based two-axis force sensor array. The advantages of our sensor array were the high sensitivity and miniaturized size of the ultrathin cross-shaped piezo-resistive silicon structure fabricated under a micropillar to detect both the normal and lateral forces acting on the micropillar. A demonstrating measurement using a water droplet with volume of 18 μL sliding on the micropillar array was carried out. The measurement results showed a fluctuation in the interaction forces when the micropillar was close to the trailing edge or leading edge of the droplet. Meanwhile, in the inner region of the contact line, both the normal and lateral interaction forces were relatively stable. These results indicate that the interaction forces at the edges of the droplet are important factors controlling the sliding motion of the droplet. © 2014 IEEE.

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Long stroke out-of-plane actuator using combination of electrostatic and pneumatic forces

T Kan, A Isozaki, H Takahashi, K Matsumoto, I Shimoyama

2014 IEEE 27th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 913 - 916 2014

ISSN 9781479935086

We propose an out-of-plane MEMS actuator with a large stroke length comparable to the size of the actuator itself. The proposed device is actuated by the combined forces of the electrostatic and the pneumatic forces. This combination of two independent forces enlarges a stable area during the actuation, resulting in a large stroke which is difficult to be achieved with only either force. The 3D profiling by the laser scanning microscopy confirmed the largest stroke of 103 μm was obtained with the 150-μm-diameter actuator area with the electric field of 5.8 × 105 V/m (330V between the electrodes) and the air pressure of 2.0 kPa. © 2014 IEEE.

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Measuring differential pressures with multiple MEMS sensors during takeoff of an insect-like ornithopter

H TAKAHASHI, K SATO, K MATSUMOTO, I SHIMOYAMA

Journal of Biomechanical Science and Engineering 9 (1), JBSE0004-JBSE0004 (Japan Society of Mechanical Engineers) 9 ( 1 ) JBSE0004 2014

Joint Work, Accepted, ISSN 18809863

In this study, the differential pressure distribution on the wing surface of an insect-like ornithopter was measured directly. Three microelectromechanical system (MEMS) differential pressure sensors were attached to a wing surface in the spanwise direction. The wing length, flapping frequency, and total weight of the ornithopter were 110 mm, 15 Hz, and 7.1 g, respectively. The attachment points corresponded to 25%, 50% and 75% of the wing length and 20% of the length of the wing chord. The ornithopter took offin anterosuperior mode without yawing or rolling. At takeoff, the flapping motion of the wing induced a periodic differential pressure between the upstroke and downstroke. The average values of the maximum differential pressures were 23.5 ± 3.5 Pa, 45.2 ± 3.4 Pa, and 96.7 ± 10.0 Pa at the wing root (WR), wing center (WC), and wing tip (WT), respectively. The maximum differential pressures shifted from the WT to WR in the spanwise direction. These results reflected the aerodynamic forces acting on the insect-like ornithopter during takeoff. © 2014 The Japan Society of Mechanical Engineers.

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Mechanical properties of few layer graphene cantilever

K Matsui, A Inaba, Y Oshidari, Y Takei, H Takahashi, T Takahata, ...

2014 IEEE 27th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 1087 - 1090 2014

ISSN 9781479935086

We report the resonant frequency measurement of few-layer (1-, 2-, and 3-layer) graphene (FLG) cantilevers by optical heterodyne interferometry. The micro-sized FLG cantilevers with and without the diamond-like carbon weights were fabricated using focused ion beam. The Young's modulus was able to be calculated from the measured resonant frequency. The calculated Young's modulus was larger than the literature data [1]. This result suggests that the overlapped structure of the FLG cantilever makes the structure rigid. © 2014 IEEE.

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Design and Fabrication of MEMS Tunable Metamaterials with Sub-micron Gap

A ISOZAKI, T KAN, H TAKAHASHI, N NEMOTO, K KONISHI, ...

電気学会マイクロマシン・センサシステム研究会資料, 71-75 MSS-14 ( 1-4.6-23 ) 71 - 75 2014

A piezoelectric cantilever with a Helmholtz resonator for sound-triggered wake-up switch

Yutaka Tomimatsu, Hidetoshi Takahashi, Takeshi Kobayashi, Kiyoshi Matsumoto, Isao Shimoyama

Journal of Micromechanics and Microengineering 23 ( 11 ) 114003 2013.10

Research paper (scientific journal), Joint Work, Accepted

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A piezoelectric flow sensor for use as a wake-up switch for a wireless sensor network node

Yutaka Tomimatsu, Hidetoshi Takahashi, Kenta Kuwana, Takeshi Kobayashi, Kiyoshi Matsumoto, Isao Shimoyama, Toshihiro Itoh and Ryutaro Maeda

Mechatronics (PERGAMON-ELSEVIER SCIENCE LTD) 23 ( 7 ) 893 - 897 2013.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 0957-4158

Power management is a fundamental issue in wireless sensor networks. In this paper, a piezoelectric flow sensor is proposed for use as a wake-up switch in a wireless sensor node to reduce power consumption. A cantilever with a Pb (Zr,Ti) O-3 (PZT) thin film detects airflow changes surrounding the wireless sensor node. A prototype of the flow sensor is used to determine the relationship between the change in flow velocity and piezoelectric voltage of the cantilever. The fabricated sensor generates a piezoelectric voltage of several millivolts when the flow velocity changes at a rate of approximately 1 m/s. (C) 2013 Elsevier Ltd. All rights reserved.

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Measurement of an airflow velocity change using a cantilever with Pb(Zr, Ti)O<inf>3</inf>

Tomimatsu Y., Takahashi H., Kuwana K., Kobayashi T., Matsumoto K., Shimoyama I., Itoh T., Maeda R.

2013 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, DTIP 2013 (2013 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, DTIP 2013) 2013.09

ISSN 9781467344777

We proposed a thin piezoelectric cantilever to measure an airflow velocity change. An airflow sensor using a PZT cantilever and a flow channel was fabricated. We measured the relationship between the airflow velocity change and the piezoelectric voltage of the cantilever. The dimensions of the sensor and the cantilever are 25 mm × 20 mm × 20 mm and 1500 μm × 1000 μm × 2 μm respectively. We evaluated the effect of the diameter of the flow channel on the sensor response. It was demonstrated that the fabricated sensor generated an output voltage of several millivolts when the airflow velocity changed at a rate of approximately 1 m/s. It was observed that the output voltage increased as the diameter of the flow channel became small. © 2013 CMP.

Micro force plate array for measurement of ground reaction force of insect running

H Takahashi, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International … 59 - 62 2013

ISSN 1084-6999

This paper reports on a micro force plate array for measurement of ground reaction forces of insect legs during running. The micro force plate is composed of a plate base and three beams whose surface and sidewall area are doped, which enable to detect both pressure and shear force. The device size and force resolution are 2000 μm × 500 μm × 20 μm (length × width × height) and 1 μN, respectively. Using this force plate array, the ground reaction forces of an ant was able to be measured. © 2013 IEEE.

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Measurement of an airflow velocity change using a cantilever with Pb(Zr, Ti)O3

Y Tomimatsu, H Takahashi, K Kuwana, T Kobayashi, K Matsumoto, ...

2013 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS … 2013

Effectiveness of bristled wing of thrips

K Sato, H Takahashi, N Minh-Dung, K Matsumoto, I Shimoyama

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems … (IEEE) 21 - 24 2013

ISSN 1084-6999

We have investigated the mechanism of a bristled wing of thrips by using an artificial cantilever-based wing. Five kinds of the artificial bristled wing, which had the similar size of the thrips wing, with a different hair gap were evaluated in a wind tunnel. Experiment results suggested that at low hair-gap-based Reynolds number (<10), the bristled areas of the wing acted as an imaginary airflow block, which increased the aerodynamic force. Meanwhile, this phenomenon did not occur at high Reynolds number (>100).

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Differential pressure distribution measurement for the development of insect-sized wings

H Takahashi, K Matsumoto, I Shimoyama

Measurement Science and Technology 24 (5), 055304 (IOP PUBLISHING LTD) 24 ( 5 ) 055304 2013

Research paper (scientific journal), Joint Work, Accepted, ISSN 0957-0233

This paper reports on the measurement of the differential pressure distribution over a flat, thin wing using a micro-electro-mechanical systems sensor. Sensors featuring a piezoresistive cantilever were attached to a polyimide/Cu wing. Because the weight of the cantilever element was less than 10 ng, the sensor can measure the differential pressure without interference from inertial forces, such as wing flapping motions. The dimensions of the sensor chips and the wing were 1.0 mm x 1.0 mm x 0.3 mm and 100 mm x 30 mm x 1 mm, respectively. The differential pressure distribution along the wing's chord direction was measured in a wind tunnel at an air velocity of 4.0 m s(-1) by changing the angle of attack. It was confirmed that the pressure coefficient calculated by the measured differential pressure distribution was similar to the value measured by a load cell.

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Design of a piezoresistive triaxial force sensor probe using the sidewall doping method

T Kan, H Takahashi, N Binh-Khiem, Y Aoyama, Y Takei, K Noda, ...

Journal of Micromechanics and Microengineering 23 (3), 035027 (IOP PUBLISHING LTD) 23 ( 3 ) 035027 2013

Research paper (scientific journal), Joint Work, Accepted, ISSN 0960-1317

In this study, we propose a triaxial force measurement sensor probe with piezoresistors fabricated via sidewall doping using rapid thermal diffusion. The device was developed as a tool for measuring micronewton-level forces as vector quantities. The device consists of a 15 mu m thick cantilever, two sensing beams and four wiring beams. The length and width of the cantilever are 1240 mu m and 140 mu m, respectively, with a beam span of 1200 mu m and a width of 10-15 mu m. The piezoresistors are formed at the root of the cantilever and the sidewalls of the two sensing beams. The sensor spring constants for each axis were measured at k(x) = 1.5 N m(-1), k(y) = 3.5 N m(-1) and k(z) = 0.64 N m(-1). We confirmed that our device was capable of measuring triaxial forces with a minimum detectable force at the submicronewton level.

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An AlN cantilever for a wake-up switch triggered by air pressure change

Y Kaiho, H Takahashi, Y Tomimatsu, T Kobayashi, K Matsumoto, ...

Journal of Physics: Conference Series 476 (1), 012122 (IOP PUBLISHING LTD) 476 2013

ISSN 1742-6588

This research reports an AlN cantilever with an air chamber for a wake-up switch triggered by air pressure change. The proposed sensor is designed to fulfil both high sensitivity and low power consumption. By combining an air chamber to the one side of the AlN cantilever surface, the barometric pressure change generates a piezoelectric voltage. Thus, a wake-up switch triggered by air pressure change can be achieved using an AlN cantilever. The size of the fabricated AlN cantilever was 2000 mu m x 1000 mu m x 2 mu m. The sensitivity to static differential pressure was 11.5 mV/Pa at the range of -20 Pa to 20 Pa. We evaluated the response of the sensor, which was composed of the AlN cantilever and the chamber of 60 ml in volume, when air pressure change was applied. The output voltage increased with increasing the applied air pressure change. It was observed that the maximum output voltage of 50 mV was generated when the air pressure change was 13 Pa.

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AlN cantilever for differential pressure sensor

Y Tomimatsu, H Takahashi, T Kobayashi, K Matsumoto, I Shimoyama, ...

2013 Joint IEEE International Symposium on Applications of Ferroelectric and … (IEEE) 336 - 339 2013

The differential pressure sensors are used for various applications. In this work, a piezoelectric differential pressure sensor using an aluminum nitride (AIN) thin film cantilever is proposed to achieve high sensitivity and low power consumption. The dimensions of the cantilever are 1500 mu m x 1000 mu m x 2 mu m. The proposed sensor needs no power consumption in the AIN sensing element in principle. The sensor design was validated by measuring the performance of the sensor, which showed sensitivity of 8.2 mV/Pa from -20 Pa to 20 Pa

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A wake-up switch using a piezoelectric differential pressure sensor

Y Tomimatsu, H Takahashi, T Kobayashi, K Matsumoto, I Shimoyama, ...

2013 IEEE Eighth International Conference on Intelligent Sensors, Sensor … (IEEE) 1 23 - 26 2013

This paper reports a wake-up switch using a piezoelectric differential pressure sensor in order to reduce the power consumption of a wireless sensor node. Air pressure change surrounding the sensor is detected by using a Pb(Zr,Ti)O-3(PZT) thin film cantilever with the dimension of 1500 mu m x 1000 mu m x 2 mu m. The sensor has high sensitivity with low power consumption due to its thin cantilever and low capacitance. The sensitivity was 2.4 mV/Pa from -30 Pa to 30 Pa. It was demonstrated that the fabricated sensor performed as a wake-up switch when pressure varies in 10 Pa with low power consumption.

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A triaxial tactile sensor without crosstalk using pairs of piezoresistive beams with sidewall doping

H Takahashi, A Nakai, N Thanh-Vinh, K Matsumoto, I Shimoyama

Sensors and Actuators A: Physical 199, 43-48 (Sensors and Actuators, A: Physical) 199 43 - 48 2013

Research paper (scientific journal), Joint Work, Accepted, ISSN 0924-4247

This paper reports on a triaxial tactile sensor using piezoresistive beams. The sensor chip is composed of two pairs of sidewall-doped Si beams for shear stress sensing and one pair of surface-doped Si beams for normal stress sensing. The sizes of the shear- and pressure-sensing beams are 180 μm × 15 μm × 20 μm and 250 μm × 50 μm × 20 μm (length × width × thickness), respectively. The sensor chip is embedded in a PDMS sheet 10 mm × 10 mm × 2 mm in size. Because the simple beam structure can be fabricated easily, the proposed sensor is compatible with semiconductor device fabrication. The fabricated sensor was evaluated for normal and shear stress (0-400 kPa and 0-100 kPa, respectively). The responses of the corresponding beam pairs were found to be proportional to the magnitude of the applied stresses without the influence of the other stresses. The relationship between the angle of shear stress and the responses of each beam pair was also evaluated. Each beam pair detects only one axis's shear stress and showed little reaction to the other axes' shear stress. As a result, the proposed sensor can measure the three axial components of normal and shear stress independently. © 2013 Elsevier Ltd. All rights reserved.

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A piezoresistive cellular traction force sensor

UG Jung, H Takahashi, T Kan, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2013 IEEE 26th International … 927 - 930 2013

ISSN 1084-6999

This paper presents a rigid piezoresistive sensor to measure cellular traction forces. The traction forces on a rigid substrate such as bone (10∼30 [GPa]) are still unknown. Our approach of the traction force measurement is not by an observation [1-4] but by a resistance change of the piezo-resistor due to the deformation of the rigid sensor (spring constant: 900 nN/μm). Because of its high sensitivity with sub-μN resolution, we were able to measure the traction forces on the rigid substrate. The stiffness of the proposed sensor was 10 times larger than that of previous works. We demonstrated that the traction forces generated by fibroblast were 0.7 μN when two cells adhered to the sensor. © 2013 IEEE.

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A piezoelectric cantilever-type differential pressure sensor for a low standby power trigger switch

Y Tomimatsu, H Takahashi, T Kobayashi, K Matsumoto, I Shimoyama, ...

Journal of Micromechanics and Microengineering 23 (12), 125023 (IOP PUBLISHING LTD) 23 ( 12 ) 125023 2013

Joint Work, Accepted, ISSN 09601317

This paper describes a piezoelectric differential pressure sensor using a cantilevered structure with dimensions of 1500 x 1000 x 2 mu m(3). A high degree of sensitivity is achieved without the power supply because only the base part of the cantilever is fixed and the piezoelectric material is used as a sensing element. The measurements indicate that the fabricated cantilever bends and a piezoelectric voltage was generated matching the piezoelectric theory for when a differential pressure is applied. The sensitivity to the applied differential pressure was 2.4 mV Pa-1 for a range between -30 Pa and 30 Pa. Additionally, it was also demonstrated that the sensor performs as a wake-up switch during the pressure shifts of 10 Pa with low-power consumption.

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A piezoelectric cantilever with a Helmholtz resonator as a sound pressure sensor

Y Tomimatsu, H Takahashi, T Kobayashi, K Matsumoto, I Shimoyama, ...

Journal of Micromechanics and Microengineering 23 (11), 114003 2013

A photoresponse-compensated parallel piezoresistive cantilever for cellular force measurements

UG Jung, K Kuwana, Y Ajiki, H Takahashi, T Kan, Y Takei, K Noda, ...

Journal of Micromechanics and Microengineering 23 (4), 045015 23 ( 4 ) 045015 2013

Research paper (scientific journal), Joint Work, Accepted, ISSN 0960-1317

This paper describes a parallel piezoresistive cantilever that is composed of a force-sensing cantilever in addition to a reference cantilever for photoresponse compensation. Piezoresistive cantilevers have been applied in many cellular mechanical measurement studies because of their high sensitivity, high time resolution and ease of handling. However, the electrical resistance changes in response to the excitation light of the fluorescence microscope, which affects the cell measurements. We measured the I-V characteristics of a piezoresistive layer. These photoresponses occurred due to the internal photoelectric effect. We canceled the photoresponses using the reference cantilever. This paper demonstrates compensation of the cantilever photoresponse under irradiation at different angles, wavelengths and light intensities. As a result, the photoresponse could be decreased by 87%. © 2013 IOP Publishing Ltd.

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A barometric pressure sensor based on the air-gap scale effect in a cantilever

N Minh-Dung, H Takahashi, T Uchiyama, K Matsumoto, I Shimoyama

Applied Physics Letters 103 (14), 143505 (AMER INST PHYSICS) 103 ( 14 ) 143505 2013

Joint Work, Accepted, ISSN 00036951

The most common structure for a conventional barometric pressure sensor consists of a vacuum-sealed cavity and a diaphragm. However, we hypothesize that a simple structure with an unsealed cavity and an ultra-thin cantilever can provide more sensitive measurements. We produced a 300-nm-thick cantilever with a small spring constant, which made the cantilever sensitive to low pressures. We demonstrated that miniaturizing the air-gap of the cantilever enables the sensor to measure barometric pressure changes at a low pressure change rate with a high resolution, which was 1 Pa at 0.05 Hz, and for a gap size of 1.7 mu m. (C) 2013 AIP Publishing LLC.

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3P172 マイクロピラーアレイ上で成長したフィブロブラスト細胞の大きさと形状 (12. 細胞生物的課題, ポスター, 日本生物物理学会年会第 51 回 (2013 年度))

T Tsukagoshi, G Jung Uijin, H Takahashi, T Kan, K Matsumoto, ...

生物物理 53 (1), S240 2013

3-axis fingertip force during playing the string instrument

M Hori, M Hosono, H Takahashi, K Matsumoto, I Shimoyama

2013 Transducers & Eurosensors XXVII: The 17th International Conference on … (2013 Transducers and Eurosensors XXVII: The 17th International Conference on Solid-State Sensors, Actuators and Microsystems, TRANSDUCERS and EUROSENSORS 2013) 2745 - 2748 2013

ISSN 9781467359818

In this paper, we propose a measurement method of 3-axis fingertip force which works when playing a string instrument. A small and thin 3-axis tactile sensor was fabricated to attach to the first finger. The force sensing elements were formed within 1 mm×1 mm on the sensor chip, and the thickness of the sensor was 3 mm. A guitar was used as a string instrument. Using the proposed method, the 3-axis fingertip force was measured in two cases; (a) when the guitar string was held down incorrectly; (b) when the guitar string was held down properly. The data of the 3-axis tactile sensor and the guitar sound were recorded simultaneously. Comparing both cases, it was indicated that the number of the guitar sound's overtone spectra was increased when the string vibration did not propagate through the finger. This proposed method will develop a significant way to analyze the relationship between musicians' fingertip force and instrument sounds. © 2013 IEEE.

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Simultaneous detection of particles and airflow with a MEMS piezoresistive cantilever

H Takahashi, T Kan, K Matsumoto, I Shimoyama

Measurement Science and Technology 24 (2), 025107 (IOP PUBLISHING LTD) 24 ( 2 ) 025107 2013

Research paper (scientific journal), Joint Work, Accepted, ISSN 0957-0233

This paper describes a particle and airflow sensor using a MEMS piezoresistive cantilever with the dimensions of 250 mu m x 200 mu m x 0.29 mu m. The sensor structure is simple and detects both the airflow velocity and particle collisions by measuring the fractional resistance change due to the cantilever bending. The signals of the airflow velocity and particle collisions can be simultaneously detected by distinguishing continuous and pulse responses. The sensitivity to the airflow velocity was 1.2 x 10(-3) (m/s)(-1) from 0 to 2.5 m s(-1). When a particle of 35 mu m diameter (Lycopodium) collided with the cantilever surface, the fractional resistance change varied with the collision. After the collision, reverberation occurred at 3 kHz, which was the same as the resonance frequency of the cantilever. The magnitude of the fractional resistance changes due to particle collision was proportional to the airflow velocity. The sensitivity to particle collision was 2.0 x 10(-3) (m/s)(-1) when the airflow velocity varied between 0 and 2.5 m s(-1).

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Regional 3-axis plantar forces during stair ascent

M Hori, H Takahashi, A Nakai, K Matsumoto, I Shimoyama

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 1033 - 1036 2013

ISSN 10846999

We proposed the measurement method of plantar force distribution during barefoot walking. 3-axis sensors were fabricated and attached on the sole of the foot. The sensors were so small, light and thin that we were able to measure the forces without interfering in the barefoot condition. Combining these sensors with wireless measurement system, we measured 3-axis plantar force distribution during level walking and stair ascent (Fig. 1). From these measurement results, we calculated zero moment point (ZMP): important index of robot walking. These results indicate that the proposed method can be suitable to analyze the mechanisms of barefoot walking. © 2013 IEEE.

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Quantitative evaluation of the influence of dopaminergic neuron on flapping locomotion

K Azuma, H Takahashi, T Kan, J Tanimura, K Ito, K Matsumoto, ...

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)) 5 - 8 2013

ISSN 10846999

This paper reports on quantitative evaluation of influence of dopamine neurons on the flight locomotion of a fruit fly (Drosophila menanogaster). The aerodynamic force was measured by MEMS triaxial forcesensor. We compared the aerodynamic force of the genetically modified flies whose dopamine neurons (DDCII) are functionally blocked with that of the wild type ones. The peak aerodynamic force generated by wild type flies was controlled smoothly. By contrast, the peak aerodynamic force generated by genetically modified flies showed rough fluctuation. The Peak variability of the wild type flies and genetically modified flies were 0.06 ± 0.04 and 0.18 ± 0.14 [-] (Average ± S.D.), respectively. The result indicated that the DDCII-expressing dopamine neurons were necessary to control their flapping flight. © 2013 IEEE.

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High sensitive 3D tactile sensor with the structure of elastic pyramids on piezoresistive cantilevers

N Thanh-Vinh, N Binh-Khiem, K Matsumoto, I Shimoyama

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems … 2013

MEMS microphone with a micro Helmholtz resonator

H Takahashi, A Suzuki, E Iwase, K Matsumoto, I Shimoyama

Journal of Micromechanics and Microengineering 22 (8), 085019 (IOP PUBLISHING LTD) 22 ( 8 ) 085019 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 0960-1317

This paper reports on the development of a micro electro mechanical system microphone consisting of a piezoresistive cantilever and a micro HR (Helmholtz resonator) for use as an ultrasonic proximity sensor. The resonance frequency of the HR was designed to be equal to that of the cantilever. Therefore, the HR increases the sensitivity of the microphone to ultrasonic waves. The dimensions of the fabricated HR and the cantilever are 1.2 mm x 1.2 mm x 0.6 mm and 130 mu m x 40 mu m x 0.3 mu m, respectively. At a resonance frequency of 22.6 kHz, the cantilever with the HR detected ultrasonic waves with 14 times greater sensitivity than that of the cantilever without the HR. We demonstrated that the fabricated sensor is capable of measuring distances between 0.5 and 6.0 m.

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Differential pressure sensor using a piezoresistive cantilever

H Takahashi, NM Dung, K Matsumoto, I Shimoyama

Journal of Micromechanics and Microengineering 22 (5), 055015 (IOP PUBLISHING LTD) 22 ( 5 ) 055015 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 0960-1317

This paper reports on a differential pressure sensor using a piezoresistive cantilever with the dimensions of 125 mu m x 100 mu m x 0.3 mu m. The sensor has a higher sensitivity than a traditional diaphragm sensor because of the three free edges of the cantilever. The measured results indicated that the fabricated cantilever bent according to theory when differential pressure was applied. The sensitivity and resolution of the differential pressure were 3.2 x 10 (4) Pa (1) and 0.02 Pa from -20 Pa to 20 Pa, respectively.

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Differential pressure measurement of an insect wing using a MEMS sensor

H Takahashi, K Matsumoto, I Shimoyama

Complex Medical Engineering (CME), 2012 ICME International Conference on … 349 - 352 2012

An insect can perform flight maneuvers such as hovering and snap turns. There have been many methods such as digital particle image velocimetry (DPIV) or kinematic analysis using robotic wings modeled on insects to investigate the aerodynamic force. The aerodynamic force is derived from the differential pressure between the upper and lower surfaces of its wings. The actual aerodynamic force on real insect wings has never been measured directly during free flight. Here we show direct measurement of differential pressure acting on the wing surface of a real insect during free flight. A micro differential pressure sensor was fabricated by utilizing micro electro mechanical systems (MEMS) and fixed to a butterfly (Papilio protenor) wing. The size and weight of the sensor chip are 1.0 mm x 1.0 mm x 0.3 mm and 0.7 mg, respectively. The differential pressures were measured during takeoff. From the measured differential pressure distribution, aerodynamic force was calculated. The maximum aerodynamic force generated on the wings was 3 times larger than the gravity acting on the body. © 2012 IEEE.

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Differential pressure distribution measurement with an MEMS sensor on a free-flying butterfly wing

H Takahashi, H Tanaka, K Matsumoto, I Shimoyama

Bioinspiration & biomimetics 7 (3), 036020 (IOP PUBLISHING LTD) 7 ( 3 ) 036020 2012

Research paper (scientific journal), Joint Work, Accepted, ISSN 1748-3182

An insect can perform various flight maneuvers. However, the aerodynamic force generated by real insect wings during free flight has never been measured directly. In this study, we present the direct measurement of the four points of the differential pressures acting on the wing surface of a flying insect. A small-scale differential pressure sensor of 1.0 mm x 1.0 mm x 0.3 mm in size was developed using microelectromechanical systems (MEMS) and was attached to a butterfly wing. Total weight of the sensor chip and the flexible electrode on the wing was 4.5 mg, which was less than 10% of the wing weight. Four points on the wing were chosen as measurement points, and one sensor chip was attached in each flight experiment. During takeoff, the wing's flapping motion induced a periodic and symmetric differential pressure between upstroke and downstroke. The average absolute value of the local differential pressure differed significantly with the location: 7.4 Pa at the forewing tip, 5.5 Pa at the forewing center, 2.1 Pa at the forewing root and 2.1 Pa at the hindwing center. The instantaneous pressure at the forewing tip reached 10 Pa, which was ten times larger than wing loading of the butterfly.

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CNT-FET gas sensor using a functionalized ionic liquid as gate

N Kiga, Y Takei, A Inaba, H Takahashi, K Matsumoto, I Shimoyama

2012 IEEE 25th International Conference on Micro Electro Mechanical Systems … (IEEE) 796 - 799 2012

ISSN 1084-6999

We propose a gas sensor using combination of carbon nanotubes (CNTs) and ionic liquid (IL). In our research, we used IL, 1-ethyl-3-methyl imidazolium tetrafluoroborate ([EMIM][BF4]) which specially absorbs CO2 / NH3, and polymer, polyethyleneimine (PEI) which absorbs CO2. This IL or the mixture of IL and PEI dropped on the CNT-FET were applied as a CNT-FET IL-gate and a surface modification material of CNTs. When the IL absorbs specific gases, the ion types and concentrations change. We measured the change of CNT I-V property by applying a voltage to the IL-gate to attract the ions onto the CNT surface.

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Carbon dioxide detection by surface plasmon resonance with ionic liquid

K Ishizu, T Kan, Y Takei, H Takahashi, K Matsumoto, I Shimoyama

2012 IEEE 25th International Conference on Micro Electro Mechanical Systems … (IEEE) 784 - 787 2012

ISSN 1084-6999

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A piezoelectric flow sensor for wake-up switch of wireless sensor network node

Y Tomimatsu, K Kuwana, T Kobayashi, T Itoh, R Maeda

2012 Second Workshop on Design, Control and Software Implementation for … 2012

A piezoelectric cantilever with Helmholtz resonator for a sound-triggered wake-up switch

Y Tomimatsu, H Takahashi, T Kobayashi, K Matsumoto, I Shimoyama, ...

Proceedings of PowerMEMS, 295-298 2012

Triaxial force sensor with strain concentration notch beam for measurement of insect flight force

K Azuma, H Takahashi, T Kan, K Matsumoto, I Shimoyama

2012 IEEE 25th International Conference on Micro Electro Mechanical Systems … (IEEE) 140 - 143 2012

ISSN 1084-6999

This paper reports on the triaxial force measurement during flapping flight of a fruit fly (Drosophila melanogaster). The total flight force was measured by a triaxial force sensor. The sensor consists of a cantilever probe, two sensing beams and four wiring beams. The total size of the sensor was 2 mm x 3 mm x 0.5 mm. A fruit fly was attached to the tip of the cantilever probe. The triaxial forces were measured when the fruit fly flapped. The measured force varied in synchronization with the flapping frequency of 240 Hz. The maximum forces in both lift and thrust directions were approximately 40 mu N.

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Shear force detector using piezo-resistive beams with sidewall-doping

H Takahashi, A Nakai, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2012 IEEE 25th International … (IEEE) 599 - 602 2012

ISSN 1084-6999

This paper reports on a shear force detector using piezo-resistive beams with sidewall doping embedded in elastic body. These beams are formed using a 20 mu m-thick device Si layer of an SOI (Silicon on Insulator) wafer. Shear force is measured by the resistance change due to the extension/compression of the sidewall. The size of the beams is 180 mu m x 15 mu m x 20 mu m (length x width x thickness). Using these shear force detectors, a triaxial tactile sensor can be fabricated.

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Measurement of the pressure distribution during the onset of slip

N Thanh-Vinh, H Takahashi, N Binh-Khiem, K Matsumoto, I Shimoyama

SENSORS, 2012 IEEE, 1-4 (IEEE) 966 - 969 2012

ISSN 1930-0395

We report on the direct measurement of the pressure distribution of the contact surface between an elastic block and a rigid plate during the onset of slip. The measurement was carried out by using an array of seven MEMS pressure sensors embedded inside the elastic block. The results showed that the external loading force in lateral direction caused the inhomogeneous change in pressure along the contact surface: the pressure in area close to the trailing edge decreased while that at area close to the leading edge increased. This result explains why the local slip always started to occur from the trailing edge where the pressure became small.

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Micro suction cup array for wet/dry adhesion

N Thanh-Vinh, H Takahashi, T Kan, K Noda, K Matsumoto, I Shimoyama

2011 IEEE 24th International Conference on Micro Electro Mechanical Systems … (IEEE) 284 - 287 2011

ISSN 1084-6999

We propose a micro suction cup array for adhesion to both dry and wet surfaces. We measured the peel-off forces of a PDMS micro suction cup array, a PDMS flat-tip micro structure array and a flat PDMS pad from both wet and dry glass surfaces. When the glass surface was wet, the peel-off forces of a PDMS flat-tip micro pattern and a flat PDMS pad decreased by more than 1.7 times and 7.0 times, respectively. On the other hand, peel-off forces of a PDMS micro suction cup array increased by over 1.1 times when the glass surface was wet. Also, in both wet and dry conditions, an array of PDMS micro suction cup adhered stronger to a glass surface than a PDMS flat-tip micro pattern and a flat PDMS pad. Furthermore, we demonstrated that the adhesion of a suction cup array can be enhanced by miniaturizing the size of the cups.

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3D airflow velocity vector sensor

NN Minh-Dung, H Takahashi, K Kuwana, T Takahata, K Matsumoto, ...

2011 IEEE 24th International Conference on Micro Electro Mechanical Systems … (IEEE) 513 - 516 2011

ISSN 1084-6999

In this paper, we propose a sensor for measuring the three-dimensional (3D) velocity vector of airflows. The sensor, which was a 10 mm spherical figure, had a laminated structure with three channels fabricated inside. The components of the airflow velocity vector were measured respectively by three piezo-resistive cantilevers fabricated in each of the three channels. Experiments with a wind tunnel demonstrated that our sensor can measure not only the velocity amplitude but the 3D velocity direction as well.

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Differential pressure distribution measurement of a free-flying butterfly wing

H Takahashi, K Matsumoto, I Shimoyama

Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS … 2022 - 2025 2011

This paper reports on differential pressure distribution measurement of a free-flying butterfly wing with a MEMS differential pressure sensor. A piezoresistive cantilever was used as a differential pressure sensor. The sensor chip was 1.0 mm 1.0 mm 0.3 mm in size and 0.7 mg in weight, respectively, so that it did not interfere with wing motion. Using a butterfly (Papilio protenor) with a sensor chip attached to the wing surface, the distribution of five points to the spanwise direction at the forewing and one point at the center of the hindwing was measured during takeoff. As a result, it was clarified that the maximum aerodynamic force generated on the wing was 3 times larger than the gravity acting on the body. © 2011 IEEE.

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Barometric pressure change measurement

N Minh-Dung, H Takahashi, K Matsumoto, I Shimoyama

Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS … 898 - 901 2011

In this paper, we report a high-sensitivity barometric pressure sensor for use in automotive navigation, personal mobile systems and environmental monitoring. The sensor consisted of an open cavity and a micro piezo-resistive cantilever, which is placed at the cavity's opening. In the proposed structure, the cavity did not need to be vacuum-sealed and the air-gap between the cantilever and its surrounding walls was micrometer order size. The cantilever was used to detect the time-variant interaction between barometric pressure and the pressure inside the cavity. Evaluation experiments demonstrate that the sensor is able to measure the barometric pressure change with high sensitivity, with expected resolution of 0.1 Pa. © 2011 IEEE.

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A gas sensor based on viscosity change of ionic liquid

K Ohsawa, H Takahashi, K Noda, T Kan, K Matsumoto, I Shimoyama

2011 IEEE 24th International Conference on Micro Electro Mechanical Systems … (IEEE) 525 - 528 2011

ISSN 1084-6999

We proposed a gas sensor based on viscosity change of ionic liquid. Our sensor consists of a piezoresistive cantilever immersed in an ionic liquid droplet. When the ionic liquid absorbs gas, the viscosity of the liquid decreases. Thus, the gas concentration is estimated by measuring the viscosity of the ionic liquid. We measured the viscosity change by monitoring the vibration amplitude of the immersed piezoresistive cantilever, which was vibrating in the ionic liquid by the magnetic field. The size of fabricated sensor chip was 1.5 mm x 1.5 mm x 0.3 mm. The cantilever and the volume of the ionic liquid droplet were 300 mu m x 200 mu m x 0.5 mu m and 0.4 mu l, respectively. We demonstrated that the vibration amplitude of the cantilever increased monotonically when acetone concentration rose from 0 to 15 mol%.

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Differential Pressure Measurement on Insect Modeled Ornithopter with MEMS Sensor in Free-flight

OHSAWA Kazuharu, AOYAMA Yuichiro, TAKAHASHI Hidetoshi, TANAKA Hiroto, IWASE Eiji, MATSUMOTO Kiyoshi, SHIMOYAMA Isao

Journal of the Robotics Society of Japan (The Robotics Society of Japan) 28 ( 9 ) 1131 - 1136 2010.11

Joint Work, ISSN 02891824

To achieve flight, an insect generates aerodynamic force by flapping its wings. However, this aerodynamic force acting on the wings has not been directly measured during free-flight. In this study, we fabricated an ornithopter modeled on a hawk moth, and attached a MEMS differential pressure sensor on its wing. Then, we measured differential pressure between upper and lower surfaces of the wing during free-flight. Reynolds number of the wing and wing load of the ornithopter were designed to be 4.2 × 103[–], and 7.5[N/m2], which were close to those of a hawk moth. The mass, wing length and flapping frequency were 6.8[g], 110[mm] and 13[Hz], respectively. The maximum differential pressures at the center of the wing were 39[Pa] and 18[Pa] during downstroke and upstroke, which were 5 and 2 times larger than the wing load. The differential pressure contributed vertical pressure of 38[Pa] during downstroke and horizontal pressure of 15[Pa] during upstroke. The time average of vertical differential pressure was 7.0[Pa], which was as large as the wing load of the ornithopter.

Differential pressure measurement on a flapping wing using a MEMS sensor

高橋英俊, 青山雄一郎, 大澤一治, 松本潔, 下山勲

可視化情報学会誌 30 ( Suppl.2 ) 207 - 208 2010.10

ISSN 0916-4731

Flight Mode Change with Wing Phase Relationship of Dragonfly-Type Flight(Fluids Engineering)

TAKAHASHI Hidetoshi, TANAKA Hiroto, MATSUMOTO Kiyoshi, SHIMOYAMA Isao

Transactions of the Japan Society of Mechanical Engineers. B (The Japan Society of Mechanical Engineers) 76 ( 768 ) 1199 - 1205 2010.08

Joint Work, ISSN 03875016

In this research, Dragonfly-type Ornithopers (DTOs) were developed to reveal the effect of the phase relationship between forewings and hindwings on flight performance. The DTO has high aspect four wings. The Reynolds number of the ornithopter is the same order as that of real dragonflies (10^3-10^4). The DTO's phase relationship ranges from 0° to 315° with 45° intervals. Flights of DTOs with various phase relationships were recorded with a high speed video camera, and their motions were analyzed. In the stable flight, the flight speed varied depending on the phase relationship. We also vis...

Measurement of differential pressure on a butterfly wing

H Takahashi, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems (MEMS), 2010 IEEE 23rd International … (IEEE) 63 - 66 2010

ISSN 1084-6999

This paper reports on direct measurement of differential pressure on a butterfly wing during free flight. Differential pressure was measured using a micro-fabricated sensor. A piezo-resistive cantilever was used as a differential pressure sensor. The sensor was 1.0 mm x 1.0 mm x 0.3 mm in size and 0.7 mg in weight so that it did not interfere with wing motion. By attaching the sensor to the center of a butterfly forewing with a flexible wiring, the differential pressure on the wing was measured during "no flight flapping" and "taking off".

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Differential pressure measurement using a free-flying insect-like ornithopter with an MEMS sensor

H Takahashi, Y Aoyama, K Ohsawa, H Tanaka, E Iwase, K Matsumoto, ...

Bioinspiration & biomimetics 5 (3), 036005 (IOP PUBLISHING LTD) 5 ( 3 ) 036005 2010

Research paper (scientific journal), Joint Work, Accepted, ISSN 1748-3182

This paper presents direct measurements of the aerodynamic forces on the wing of a free-flying, insect-like ornithopter that was modeled on a hawk moth (Manduca sexta). A micro differential pressure sensor was fabricated with micro electro mechanical systems (MEMS) technology and attached to the wing of the ornithopter. The sensor chip was less than 0.1% of the wing area. The mass of the sensor chip was 2.0 mg, which was less than 1% of the wing mass. Thus, the sensor was both small and light in comparison with the wing, resulting in a measurement system that had a minimal impact on the aerodynamics of the wing. With this sensor, the 'pressure coefficient' of the ornithopter wing was measured during both steady airflow and actual free flight. The maximum pressure coefficient observed for steady airflow conditions was 1.4 at an angle of attack of 30 degrees. In flapping flight, the coefficient was around 2.0 for angles of attack that ranged from 25 degrees to 40 degrees. Therefore, a larger aerodynamic force was generated during the downstroke in free flight compared to steady airflow conditions.

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Sound direction sensor with an acoustic channel

MD Nguyen, A Inaba, A Suzuki, H Takahashi, E Iwase, K Matsumoto, ...

2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems … (IEEE) 655 - 658 2010

ISSN 1084-6999

This paper reports on a method for estimating direction of a sound with one directional acoustic sensor. Inspired by the two input structure of bushcricket ear, our sensor was designed to have an acoustic channel and a micro piezo-resistive cantilever. The radiated sound acts simultaneously on the external and on the inner surface of the cantilever. As the result, the directionality of our sensor varies with the frequency of incident sound. The sound direction was estimated by using directional responses of the sensor at multiple frequencies so that it does not require either angle scanning or microphone arrays. We demonstrated that this method enables the sound direction to be estimated with the average error of 4 degrees in laboratory experiments.

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Photo-response compensated piezoresistive cantilever for use in fluorescence microscopy

U Jung, K Kuwana, H Takahashi, T Kan, Y Takei, K Noda, E Iwase, ...

2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems … (IEEE) 588 - 591 2010

ISSN 1084-6999

This paper presents the design, fabrication, and the characterization of a photo-response compensated piezoresistive cantilever. The application field of the cantilever is to measure cellular mechanical properties under fluorescence microscopy. Photo-response which is caused by an excitation light of a fluorescence microscope interferes with measurement. We proposed piezoresistive cantilevers consist of a force-sensing cantilever with a reference cantilever to cancel out the photo-response. We measured the photo-response of the fabricated device, by varying wavelength, light intensity and light incidence angle. The experimental results show that the photo-response was decreased by 87%. This verified that present device has effective photo-response compensation by using the reference cantilever.

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Flight mode change with wing phase relationship of dragonfly-type flight

H Takahashi, H Tanaka, K Matsumoto, I Shimoyama

Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of … 2010

平面型微小コイルを用いた局所高感度MRI

土肥徹次, 高橋英俊, 松本潔, 下山勲

生体医工学 (Japanese Society for Medical and Biological Engineering) 47 ( 16 ) 484 - 493 2009.12

Joint Work, Accepted, ISSN 1347-443X

In this study, we fabricated micro planar coils as a receiver for a high sensitive MRI (Magnetic Resonance Imaging). According to the calculation of the scale effect, the sensitivity of the coil increases with decrease of the diameter of the coil under the condition of fixed inductance. The micro planar coils of 5 and 20 mm in diameter were fabricated by using MEMS technology. The resistance and inductance of the 20 mm coil were 1.4 Ω and 1.15 μH at 8.5 MHz, respectively. Those of the 5 mm coil were 2.0 Ω and 1.05 μH, respectively. The MRI signal receivers were made by attaching the micro coils to the tip of acrylic pipes. The SNRs (Signal to Noise Ratio) of MR images of phantom were measured by the micro planar coils and the medical MRI coil of 200 mm in diameter. The SNRs of MR images taken by the micro planar coils were about 8 times as high as the MR image taken by the medical coil. MR images of an okra (Abelmoschus esculentus) were acquired by fabricated MRI signal receivers with the voxel size of 2.0 × 2.0 × 2.0 mm3 and 0.5 × 0.5 × 1.0 mm3. Since the sensitivity of micro planar coils was high, we were able to clearly observe inner structure of the okra.

Sensitivity enhancement by micro Helmholtz resonator for ultrasonic distance sensor

A Suzuki, H Takahashi, E Iwase, K Matsumoto, I Shimoyama

TRANSDUCERS 2009-2009 International Solid-State Sensors, Actuators and … 1557 - 1560 2009

This paper reports on a micro Helmholtz resonator (HR) enhancing the sensitivity of an ultrasonic distance sensor. Attaching an HR to the sensor that consists of a piezoresistive cantilever microphone makes its sensitivity against ultrasonic wave higher. A HR of 600 μm height demonstrated a 17.5 times larger maximum amplitude of the cantilever vibration against single frequency wave. We also evaluated the dependence of the sensitivity on frequency and acoustic pressure. Our sensor was able to detect the distance of 0.5-6.0 m with the maximum error of 2.0%. ©2009 IEEE.

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Air pressure sensor for an insect wing

H Takahashi, K Matsumoto, I Shimoyama

Micro Electro Mechanical Systems, 2009. MEMS 2009. IEEE 22nd International … (IEEE) 825 - 828 2009

ISSN 1084-6999

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Local high sensitive MRI with a micro planar coil

T Dohi, H Takahashi, K Matsumoto, I Shimoyama

Transactions of Japanese Society for Medical and Biological Engineering 47 … 47 ( 6 ) 484 - 493 2009

ISSN 1881-4379

In this study, we fabricated micro planar coils as a receiver for a high sensitive MRI (Magnetic Resonance Imaging). According to the calculation of the scale effect, the sensitivity of the coil increases with decrease of the diameter of the coil under the condition of fixed inductance. The micro planar coils of 5 and 20 mm in diameter were fabricated by using MEMS technology. The resistance and inductance of the 20 mm coil were 1.4 Ω and 1.15 μH at 8.5 MHz, respectively. Those of the 5 mm coil were 2.0 Ω and 1.05 μH, respectively. The MRI signal receivers were made by attaching the micro coils to the tip of acrylic pipes. The SNRs (Signal to Noise Ratio) of MR images of phantom were measured by the micro planar coils and the medical MRI coil of 200 mm in diameter. The SNRs of MR images taken by the micro planar coils were about 8 times as high as the MR image taken by the medical coil. MR images of an okra (Abelmoschus esculentus) were acquired by fabricated MRI signal receivers with the voxel size of 2.0 × 2.0 × 2.0 mm3 and 0.5 × 0.5 × 1.0 mm3. Since the sensitivity of micro planar coils was high, we were able to clearly observe inner structure of the okra.

Air flow senser for an insect-like flapping wing

H Takahashi, E Iwase, K Matsumoto, I Shimoyama

2008 IEEE 21st International Conference on Micro Electro Mechanical Systems … (IEEE) 916 - 919 2008

ISSN 1084-6999

This paper reports on a thin piezoresistive cantilever for measuring air flow velocity around flapping wings. To measure the air flow velocity at a point of the wing directly, our sensor was attached to the leading edge of the wing. The sensor was designed to be I pin thick. Because of the scale effect, the influence of the inertial force was small during flow measurement. The sensor had the sensitivity of 0.56 - 0.96 - 10(-3) (m/s)(-2) as well as the directivity By using the micro flow sensor, we measured the perpendicular air flow velocity at the point of the leading edge of the wing.

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A micro planar coil for local high resolution magnetic resonance imaging

H Takahashi, T Dohi, K Matsumoto, I Shimoyama

2007 IEEE 20th International Conference on Micro Electro Mechanical Systems … (IEEE) 786 - 789 2007

ISSN 1084-6999

This paper reports on a flexible micro planar coil for an MR (Magnetic Resonance) catheter. High resolution images can be obtained by using the MR catheter. Two types of coils of 5 mm and 20 mm in diameter were fabricated. Both of the coils were designed to have inductance of 1.0 mu H at 8.5 MHZ. The proto-type MR catheters were made by attaching the micro coils to the tip of acrylic pipes. In order to evaluate the MR catheters, the sensitive area and SNR (Signal to Noise Ratio) were measured. SNRs of the MR catheters were about three to eight times higher than that of a standard medical coil. Furthermore, we demonstrated that high resolution MR images can be achieved by using the MR catheters. MR images of a gumbo (Abelmoschus esculentus) were acquired with 0.5 x 0.5 x 1.0 mm(3) resolution. While clear MR images were not able to be taken by the standard medical coil due to its low SNR, we were able to observe the gumbo and distinguished its seeds one by one in the MR images taken by the MR catheters.

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