論文 - 高橋　英俊

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 （Journal of Micromechanics and Microengineering）  27 （ 7 ） 075017 2017年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  09601317

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© 2017 IOP Publishing Ltd. 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 μm 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 μm × 400 μm plate supported by two 150 μm long, 4 μm 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-1is 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 （Applied Physics Letters）  111 （ 26 ） 263503 2017年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00036951

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© 2017 Author(s). 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.

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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 （Journal of Microelectromechanical Systems）  26 （ 5 ） 990 - 992 2017年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  10577157

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© 1992-2012 IEEE. 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.

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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年

Pressure sensor

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

US Patent App. 15/512,701 2017年

MEMS差圧センサを搭載した羽ばたき機

高橋 英俊, 下山 勲

日本ロボット学会誌 （一般社団法人 日本ロボット学会）  35 （ 9 ） 660 - 663 2017年

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定常風下でのハエの飛翔力計測

萩原 岳大, 高橋 英俊, 矢野 朋子, 伊藤 啓, 髙畑 智之, 下山 勲

ロボティクス・メカトロニクス講演会講演概要集 （一般社団法人 日本機械学会）  2017   1A1 - J11 2017年

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<p>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.</p>

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前翅固定翼による羽ばたき飛翔への影響の計測

阿部 公亮, 高橋 英俊, 髙畑 智之, 下山 勲

ロボティクス・メカトロニクス講演会講演概要集 （一般社団法人 日本機械学会）  2017   2A1 - M03 2017年

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<p>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.</p>

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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年

ISSN  9781509039142

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© 2016 IEEE. Small insects have agile performance in flight, walking locomotion, and so on. Currently, many researchers have been focusing the dynamics of their locomotion. We have been developing micro scaled piezoresistive force sensors to measure forces exerted by insects during flying, walking and jumping. In this paper, we introduce these sensors which are specialized for target insects.

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Gas sensor

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

US Patent 9,250,210 2016年

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, ...

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems … （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2016-February   165 - 168 2016年

ISSN  9781509019731

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© 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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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年

ISSN  9781509019731

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© 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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Pressure sensor

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

US Patent App. 15/117,272 2016年

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 （Langmuir）  32 （ 37 ） 9523 - 9529 2016年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  07437463

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© 2016 American Chemical Society. 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年

ISSN  9781943580118

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© 2016 OSA. We proposed a chiral switchable metamaterial using MEMS technology in the terahertz frequency region. Deformation of a flat metal spiral unit of the metamaterial creates three-dimensional spirals, and symmetrical chiral switching of the spiral could be performed by selecting the deformation directions; upper or lower. Ellipticity modulations amplitude as large as ±28° could be obtained in 1.08 THz, and optical responses were numerically analyzed.

Cantilever with 10-fold tunable spring constant using Lorentz force

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

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems … （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2016-February   866 - 868 2016年

ISSN  9781509019731

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© 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 （Sensors (Switzerland)）  16 （ 5 ） 718 2016年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  14248220

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© 2016 by the authors; licensee MDPI, Basel, Switzerland. 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年

ISSN  9781509019731

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© 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

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems … （Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS)）  2016-February   843 - 845 2016年

ISSN  9781509019731

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© 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年

共著, 査読有り

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© 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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