Kyouhei Terao

Fabrication and evaluation of polymer MEMS mirror based on the mechanical characteristic of polymer containing magnetic particles

In this study, we have evaluated the mechanical characteristic and the attractive force of the SU-8 containing magnetic particles. Then, we have fabricated the mirror device based on the mechanical characteristic of the polymer and evaluated the deflection characteristic. Two kinds of the mirror devices composed of SU-8 containing Fe<inf>2</inf>O<inf>3</inf> (particle size: p.s.5μm) and Fe<inf>3</inf>O<inf>4</inf> (p.s.5μm) particles are fabricated and evaluated. The optical deflection angles of both devices are ±20° in a small current. Then, we confirmed the possibility to realize the low cost and large deflection angle polymer MEMS mirror using SU-8 containing magnetic particles.

Improvement of processing reproducibility for a magnetic-driven microstructure made of photosensitive nanocomposite

In this paper, we investigate the reproducibility of a fabrication method for making active microstructures as micro-actuators for optical and/or fluidic micro-components. The proposed method uses a magnetic photosensitive nanocomposite made by mixing magnetic nanoparticles into photoresist without laborious processes. In the development process, the magnetic particles are taken off from the nanocomposite, and the reproducibility is drop down. It is experimentally confirmed that the dropout of the particles are reduced by increasing the exposure dose of the patterning for the active membrane made of the PNC.

Design and fabrication of polymer MEMS mirror based on the mechanical characteristic evaluation of polyimide materials

We fabricated millimeter size tensile specimens using the photosensitive polyimide as the moving part of the our proposed polymer MEMS mirror device. The mechanical characteristics of the polyimide are evaluated in the temperature range of −50∼300°. As the result, Youngs modulus and tensile strength of the photosensitive polyimide also decreased as the temperature increased, but there was no substantial change in the characteristic values in the supposed usage temperature range of −10∼70°. Based on the results, the polymer MEMS mirror torsion bar was designed and the deflection value was simulated by FEM analysis. The designed and measured angles show relative good agreement.

Low cost and large deflection angle polymer MEMS mirror using glass substrate

In this paper, we propose a polymer MEMS mirror device which has the futures of the large deflection angle and the low cost fabrication. Many conventional MEMS mirror devices have been composed of Si wafer and, the expensive dry etching equipment has been necessary when etching the Si substrate. Then, we propose new composition and the novel fabrication method without the dry etching process by using the inexpensive glass substrate. Also, the torsion bar is composed of a photosensitive polymer that is a low rigid material and can be easily fabricated by the photolithography process. A multilayer wiring process is examined so that the low current actuation and the large deflection angle is attained. The fabricated device showed the large optical deflection angle of more than ±40 degrees at the current of ±16mA when the torsion bar length was 1800µm. The variation of the optical deflection angle was within 0.8 degrees at the 106 times repeatability test.

A robust and sensitive silicon tactile imager with individually formed SU-8 protective layers on piezoresistor pixels

In this paper, a new structure of silicon tactile imager with SU-8 protective layer is presented. The protective layer is formed on the surface of integrated piezoresistor array to prevent direct contact of the sensor surface to the object. The protective layer is formed individually on each pixel circuit to prevent degradation of the spatial resolution. This tactile imager is fabricated by an established post-CMOS process without any process damage to the MOS integrated circuits. The independent protective layer is simply formed by a single step of SU-8 lithography on the pixel array. The experimental device fabricated in this study integrates 5×5 array of piezoresistors on a silicon 10µm-thick diaphragm fabricated by an SOI active layer. The scale of integration and the pitch of the piezoresistor pixel array (800µm) are determined by the feature size of circuit fabrication technology and the minimum resolution of the SU-8 lithography process. In the fabricated device, both high sensitivity and spatial resolution are obtained by the new structure with high robustness.

Development of high resolution electrostatic tactile display

In this study, we demonstrate an electrovibration tactile display with an array of electrodes. Electovibration is a promising stimulus method for tactile feedback in mobile devices. The electrovibration tactile displays have been developed for the last several decades. However, these studies focused on application of the tactile display. The resolution of the tactile display, which is important for tactile sensation, is not investigated. In this study, we developed a electrovibration tactile display with high resolution. The tactile display consists of an array of electrodes with the width of 0.95 mm. The electrodes are arranged with the interval of 0.05 mm. The resulting resolution is 1 mm. We established the fabrication process of the tactile display and evaluated the fundamental characteristics. The results indicated that the perception was determined by the amplitude of the applied voltage. And also, the perception was not related to the contacting area and applied voltage. The proposed tactile display was able to present a spatial electrovibration stimulus and required optimization of the applied voltage.

Low cost polymer MEMS mirrors fabricated by photolithography and wet etching processes

This paper presents two types of low cost mirror devices composed of the glass and the polymer material. These devices are new constructions composed of the inexpensive glass as the mirror substrate and the polymer as the torsion hinge. The devices can be fabricated by the photolithography and wet etching processes without deep-RIE process. The proposed one construction is the Lorentz force type mirror device made of polyimide material. And the other construction is the electromagnet force type mirror device made of SU-8 material containing the magnetic particles. In the former type mirror, the mirror device was fabricated without expensive dry etching equipment such as RIE, and the device can be fabricated only by the sputtering, photolithography and wet etching processes. Further, the inexpensive glass and polymer material are used instead of expensive Si. In the latter type mirror, the SU-8 polymer material containing the magnetic particles is used. The actuation system which attracts the mirror directly with the electromagnet is adopted. We fabricated the large-sized mirror (20mm × 10mm) device without expensive dry etching equipment such as deep-RIE, and evaluated the characteristics of the fabricated mirror device. The optical deflection angle of ±20deg. was achieved. As the result, we confirmed the feasibility to realize the low cost polymer MEMS mirror.