Details of a Researcher - Takahashi, Hidetoshi

Papers - Takahashi, Hidetoshi

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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

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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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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