Fumikazu Oohira

Kagawa University, Takamatu, Kagawa, Japan

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Publications (42)28.12 Total impact

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    ABSTRACT: In this paper, the influences of pretreatment and hard baking on the mechanical characteristics of SU-8 microstructures are described. Four types of samples with different combinations of O2 plasma ashing, primer coating and hard baking were prepared for shear strength tests and uniaxial tensile tests. Specially developed shear test equipment was used to experimentally measure the shear adhesion strength of SU-8 micro posts on a glass substrate. The adhesiveness was strengthened by hard baking at 200 °C for 60 min, whereas other pretreatment processes hardly affected the strength. The pretreatment and hard baking effects on the adhesive strength were compared with those on the fracture strength measured by uniaxial tensile testing. There were no influences of O2 plasma ashing on both the strengths, and primer coating affected only tensile strength. The primer coating effect as well as the hard baking effect on stress relaxation phenomena in uniaxial tension was observed as well. Fourier transform infrared spectroscopy demonstrated that surface degradation and epoxide-ring opening polymerization would have given rise to the primer coating effect and the hard baking effect on the mechanical characteristics, respectively.
    Journal of Micromechanics and Microengineering 09/2013; 23(10):105016. · 1.79 Impact Factor
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    ABSTRACT: Repeatability of driving characteristics of a polymer-MEMS mirror are transitioned by an environment and time course change. In this study, we propose a method of motion sensing for the purpose of laser scan stable by the active control of a polymer-MEMS mirror. A proposed motion sensor is a coil-type sensor that induces the electric current by an electromagnetic induction and monolithically integrated on the mirror driving by the electromagnetic force. The fabricated mirror made of SU-8 polymer deflects over ±30deg. at low electric current. The measured current induced by the integrated sensor coil is clearly obtained by applying the lock-in detection for signal processing method, and it indicates that the feasibility of amplitude control of the polymer MEMS mirror.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
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    ABSTRACT: We propose a simple fabrication method for a dual-axis polymer MEMS mirror made of negative photoresist SU-8 containing magnetic nanoparticles as a magnetically driven actuator. The proposed mirror is driven by magnetic attractive force using external magnetic field. So, it doesn't need complex wiring patterns and can simply fabricate by photolithography only. For evaluation of drive characteristics of the proposed mirror, we measured static deflection angle and frequency response of the fabricated mirror by using a laser position sensor. As a result, we obtained optical deflection angle ±15deg. and the second resonant frequency 29.2Hz of torsional oscillation.
    Optical MEMS and Nanophotonics (OMN), 2013 International Conference on; 01/2013
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    ABSTRACT: An integrated microcell culture system to control physical conditions in a microenvironment is proposed. The authors quantitatively evaluated the cytotoxicity of commonly used MEMS materials, that is, glass, negative photoresist SU-8, polystyrene and poly(dimethylsiloxane), by using the proposed system. In consequence, in these materials were not seen the cytotoxicity regarding the proliferation. Since the cellular adhesiveness and the proliferation were correlated roughly with the surface free energy. Hence, the surface free energy is one of the important parameters for evaluating the cytotoxicity of MEMS materials.
    Micro & Nano Letters 07/2012; · 0.85 Impact Factor
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    ABSTRACT: We propose a novel surface plasmon resonance (SPR) sensor chip with a microfabricated slit array. The microslit excludes micrometre-size objects larger than its slit size from the SPR sensing area, so that it functions as an in situ filter. We demonstrated the sensing of microparticles of different diameters using the chip, and the results show a successful size-exclusion effect. As a demonstration of the biological application, we performed the detection of aggregation and disaggregation of biological particles using sugar-chain-immobilized gold nanoparticles as a test sample.
    The Analyst 03/2012; 137(9):2192-8. · 4.23 Impact Factor
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    ABSTRACT: In this paper, we propose a simple fabrication technique for making active membranes as micro-actuators on a chip. By controlling three important factors consisted of the thickness of the exposure, the thickness of spin coat at surface, and the total thickness of the nanocomposite coated on a substrate, we simply form and release an active membrane layer without an alignment process. The active membrane fabricated by the proposed method actuated with the maximum displacement of 300nm at the magnetic field of 65kA/m and had good controllability.
    Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) 01/2012;
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    ABSTRACT: In this paper, design and fabrication results of 'in-plane' type MEMS mirror device driven by rotational electrostatic actuators with angle sensing ability are reported for the first time. This MEMS mirror realizes rotational motion of a vertical mirror mounted on the SOI actuator stage, which can deflect or switch the reflected light angle in parallel to the same chip surface. Since optical fibers and the vertical mirror can be aligned with guide structures or slits fabricated by the same photolithography step, precisely self-aligned micro optical bench system with light deflection function can be easily constructed. In addition, electrostatic rotary encoder is integrated with the rotational actuator for detection of the absolute rotational angle of the mirror stage. The rotational actuator device was fabricated successfully, and ±2.4° stage rotation was obtained at a 96V actuator drive voltage. Also, in-plane optical light deflection has been successfully demonstrated with the rotational mirror put on the actuator.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
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    ABSTRACT: 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.
    Optical MEMS and Nanophotonics (OMN), 2012 International Conference on; 01/2012
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    ABSTRACT: The electrodeposition of gold nanostructures increases the surface area of a biosensor, which brings an enhancement of the sensitivity by increasing the amount of analyte binding to the surface. To evaluate the relationship among the surface structure, the area and the analyte binding, we quantitatively analyzed them for quartz crystal microbalance (QCM) sensing by scanning electron microscopy and cyclic voltammetry measurements. The results indicate a several-times increase of analyte bindings, and also the limitation of the sensing performance.
    Analytical Sciences 01/2012; 28(3):291-4. · 1.57 Impact Factor
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    ABSTRACT: In this study, we propose an integrated micro cell culture system to easily carry out loading, culturing, observation, and collection of biological cells in a microchannel, and quantitatively evaluated the several factors concerning with the cells in the micro-environment. Especially, we evaluated the effect of the substrate material for the cell culture, and the adhesion and the proliferative properties of the cells collected from the microchannel. It was confirmed that the proposed micro cell culture system is useful for a practical use in cell biology.
    Nano/Molecular Medicine and Engineering (NANOMED), 2012 IEEE 6th International Conference on; 01/2012
  • Sensors and Actuators A Physical 01/2012; · 1.84 Impact Factor
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    ABSTRACT: In this paper, the first air-flow based multifunctional tactile display with 1-D mixed array of integrated air nozzles and multi-jet integrated micro venturi atomizers are presented. This device realizes simultaneous tactile presentation of “object surface shape” by distributed air-flow pressures and “sense of cold (cryesthesia)” by arrayed liquid mist injection. A new type venturi atomizer with multi jet structure was developed to control the mixture ratio of different liquids for temperature control. 2-D tactile display can be realized by simply stacking the 1-D array devices. Through the evaluations with fabricated devices, multifunctional and distributed tactile presentation has been successfully demonstrated for the first time.
    Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) 01/2012;
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    ABSTRACT: We propose a novel Kretschmann-type surface plasmon resonance (SPR) sensor chip having a surface covered with electrodeposited gold nanostructures to enhance the sensitivity of SPR biosensing. The nanostructure is three-dimensional and has a larger surface area than a conventional flat surface chip, which increases the amount of protein binding and also induces a large change in the effective dielectric constant of the sensing area. The gold nanostructures were formed by electrodeposition under galvanostatic conditions, so their size could be controlled by manipulating the deposition time and current. The sensing characteristics, including the concentration dependence and noise level, indicated that the performance of the resulting chip (called a Au-black chip) was equivalent to that of a conventional sensor chip. We also determined the optimal electrodeposition conditions to obtain a sharp SPR curve for protein detection assay; the optimal thickness of the gold layer was 50–60 nm. Enhanced protein sensing was demonstrated by using a binding assay of anti-BSA antibody and BSA molecules. The protein binding signal was several times higher than that of the conventional assay. The insights into electrodeposition for SPR sensing presented here will enable improved sensitivity for detecting low-concentration and small proteins.
    The Analyst 01/2012; · 3.97 Impact Factor
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    ABSTRACT: This paper reports an innovative design methodology of micro fluidic integrated circuits based on the CAD system of electronic circuit design. The “SPICE” program which is the most common circuit simulator in the LSI technology is applied to design micro fluidic circuits in this study. Pneumatic microvalves (pneumatic-FETs) are the active devices in the fluidic circuits, and its SPICE model is required for circuit simulation. The simulation results using the established SPICE model showed very good agreement with the characteristics of the measured circuits. This paper is the first successful demonstration of SPICE simulation in micro fluidic circuits design.
    Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) 01/2011;
  • IEEJ Transactions on Sensors and Micromachines 01/2011;
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    ABSTRACT: This paper describes the possibility of the crystalline anisotropic etching of single-crystal silicon using a fully dry etching process. Conventionally, the crystalline anisotropic etching of silicon has been achieved only using specific wet solutions. In the proposed method, the anisotropic etching is made dominant by controlling the etching energy under specific dry etching conditions. The maximum crystalline anisotropic degree is 68% at present. It is expected that complicated three-dimensional microscale silicon structures can be formed by the fully dry process proposed in this paper. INTRODUCTION Anisotropic chemical wet etching of single-crystal silicon wafers has long been used for fabricating many MEMS devices such as sensors for pressure, force, flow, and acceleration because of the advantages of batch processing and the precise controllability of the shape and dimensions of microstructures (1). In recent years, the demand for more complicated three-dimensional (3D) microstructures on a silicon chip has been increasing for various applications. To fabricate complicated 3D microstructures of silicon, dry etching techniques have several advantages: better process control, cleanliness, easy and safe treatment of the etching gas, and good compatibility with electric circuits compared with the wet process. The conventional dry etching techniques for silicon give an isotropic profile or a vertical anisotropic profile, which can be formed by repeating etching and overcoat-forming processes in the vertical direction such as the Bosch process (2). The critical parameters in vertical anisotropic dry etching have been intensively investigated during the last ten years (3). Several etching profiles have been obtained by effects such as reactive ion etching (RIE) lag (4), inverse RIE lag (5), microloading (6, 7), aspect- ratio-dependent etching (8), charging (9, 10), and so forth. Furthermore, crystalline anisotropic etching techniques except for a wet process have been demonstrated by a cryogenic dry etching (11,12) and a photo excited etching (13,14). These dry etching techniques can be done under special conditions with the specific etching machines. So, there have been no previous studies in which the RIE process at normal temperature depending on the crystal orientation of single-crystal silicon has been observed. In this paper, we report the crystalline anisotropic etching of single-crystal silicon using a fully dry process at normal temperature by controlling the pressure and RF power of the etching structures and etch rates were performed comparing and valuating. METHOD A conventional parallel-type RIE machine (RIE-10NR, SAMCO) was mainly used as the dry etching equipment in this study. A schematic configuration of the proposed dry etching process is shown in Figure. 1(a). The silicon layer is etched by the etching species such as radicals, atoms, and ions passing through a circular etching hole. When the specific RIE parameters were a pressure of 20 Pa, an RF power of 50 W, and a SF6 gas flow rate of 50 sccm, and a S1805 resist (Shipley Co.) was used as both a protective layer and a carbon source, it was observed that inverse pyramidal grooves with a dominant (111) etching surface appeared as shown in Figure. 1(b) and 1(c). The tapered angle in the cross section is about 55%, which is the same as that for anisotropic wet etching, but marked underetching occurred under the mask edges. When protective layers made of aluminum and SiO2, which contain no carbon, were used, the etching profiles were normal isotropic under the same RIE parameters. When similar dry etching processes were carried out using other resists, OMR, PMER (Tokyo Ohka Kogyo Co., Ltd.), and SU-8 3000 (Nippon Kayaku Co., Ltd.), the (111) etching surface was also dominant. Moreover, since
    Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS) 01/2011;
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    ABSTRACT: In this paper, a silicon integrated triaxial tactile imager with 800µm-pitch sensor pixel circuits and its real-time demonstration of slipping motion detection are presented for the first time. Distributions of normal- and shear-force components on contacting object surface are independently detected by the triaxial micro force sensor pixels on a flexible silicon diaphragm. The minimum force resolutions of each triaxial force sensor are below 5mN, and the cross-axis errors are below 3%. The new device structure of triaxial tactile imager can cope with both high spatial/force resolution and high adaptability to the object surface. Also, the beginning point of slipping can be specified by the individually formed fingerprint structures on the high-density multi-axis force sensor circuits. This is the first triaxial tactile imager which can be compared with human fingertip functions on the sensing performance of slip detection.
    01/2011;
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    ABSTRACT: Proposal of High-Density Packaging Construction and Conductive Pattern Forming Method on Vertical Wall Using Spray Coating Technology
    IEEJ Transactions on Sensors and Micromachines 01/2011; 131:40-44.
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    ABSTRACT: 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 Fe2O3 (particle size: p.s.5μm) and Fe3O4 (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.
    01/2011;
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    ABSTRACT: 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, Young's 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.
    01/2011;