Papers - Takahashi, Hidetoshi

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

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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

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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

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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

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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

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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

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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

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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

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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

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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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