Papers - Takahashi, Hidetoshi

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

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© 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

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© 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

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© 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

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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

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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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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

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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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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

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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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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

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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

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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

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 (MDPI AG)  16 ( 5 ) 718 2016

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

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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

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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

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

Joint Work, Accepted

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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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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, ...

2016 IEEE 29th International Conference on Micro Electro Mechanical Systems … (Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS))  2016-February   839 - 842 2016

ISSN  9781509019731

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© 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

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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

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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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© 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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