Papers - Takahashi, Hidetoshi

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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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

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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

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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

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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

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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

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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.

• Access to Document (DOI)

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

　View Summary

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.

• Access to Document (DOI)

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

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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

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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

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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