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ABSTRACT: The present research report a fabrication process of suspended silicon microstructures of desired thickness over controlled depth micromachined cavities. The process is developed using direct wafer bonding to seal the micromachined cavities and wet anisotropic etching in pure and surfactant added tetramethyl ammonium hydroxide (TMAH) solutions. Wet anisotropic etching is used for the formation of cavities, thinning down the wafer for structural layer and releasing the structures. Non-ionic surfactant Triton-X-100 [C<sub>14</sub>H<sub>22</sub>O(C<sub>2</sub>H<sub>4</sub>O)<sub>n</sub>] added TMAH is used to realize the microstructures with rounded concave and sharp convex corners.
Micro-NanoMechatronics and Human Science, 2008. MHS 2008. International Symposium on; 12/2008
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ABSTRACT: The fabrication of micro- and nanoelectromechanical systems (MEMS/NEMS) is based on a wide variety of growth and etching technologies sequentially applied throughout process flows which may involve a dozen or more steps, their realistic simulation having become an essential part of the overall design. By focusing in the simulation of anisotropic etching as a complex example of microfabrication, in this paper, we show how to solve analytically the time evolution of the continuous cellular automaton method, thus providing a particularly suitable choice for the realization of realistic simulations for MEMS and NEMS applications. This paper presents a complete theoretical derivation of the analytical solution based on geometrical and kinetic aspects of step flow on any surface, including a new classification of the surface sites based on a mean-field treatment of the propagation of the steps. The results of the corresponding simulations are in good agreement with the experiments. The study can be seen as an example of a general procedure that is applicable to other interface propagation problems.
Journal of Microelectromechanical Systems 05/2008; · 2.10 Impact Factor
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ABSTRACT: We previously proposed a novel type of on-wall in-tube thermal flow sensor, and experimentally evaluated its performance. The sensor has an advantage that it can measure the flow-rate both at near the tube entrance (hydraulically developing region) [1] and at bent tube (axially asymmetric flow) [2]. With the requirements of further miniaturization of the sensor in the fields of the portable fuel cells and chemical analyzers, we newly developed the fabrication process to miniaturize it less than 2.0 mm in external diameter by using a heat shrinkable tube. The film sensor fabricated by photolithography was inserted inside tube manually. By applying heat shrinking process, the film was automatically mounted on the inner wall surface, and the outer size of the tube was miniaturized to almost of the half size from its original. The final inner and outer diameters of the tube were 1.2 mm and 1.7 mm, respectively. We evaluated the fundamental performance of this flow sensor. The electrical resistance at the sensor linearly increased with temperature. The obtained temperature coefficient of resistance of the sensing element was 0.0023 K<sup>-1</sup>. We measured the relationship between the input power consumption and the gas flow rate, and finally evaluated the response time. We obtained a value of 100 msec by forming a cavity structure under the heat element.
Micro Electro Mechanical Systems, 2008. MEMS 2008. IEEE 21st International Conference on; 02/2008
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ABSTRACT: We proposed novel type of a sample divider, which can easily divide the sample solution into multiple small amount of it on a chip, for single molecule analysis. We used the composite of a PDMS and an expancel<sup>R</sup> as a material, and fabricated the sample divider structure by applying the mold process. We investigated the PDMS and the expancel mixture fraction dependency, and effect of the heating time, on the channel closing performance. The flow channels were successfully closed when the volume ratio between the expancel and PDMS solution was 1:2 and the heating time was 15 minutes. From these results, we concluded that the proposed device is useful as the sample divider, if we optimally designed.
Micro Electro Mechanical Systems, 2008. MEMS 2008. IEEE 21st International Conference on; 02/2008
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ABSTRACT: We have developed an improved anisotropic wet etching process for the fabrication of various silicon microstructures with rounded concave and sharp convex corners, grooves for chip isolation, meandering micro-fluidic channels, mesa structures with bent V-grooves, and 45deg mirrors with highly smooth surface finish by using a single etching mask on (100) wafers. In this work, we use a CMOS compatible anisotropic etchant containing tetramethyl ammonium hydroxide (TMAH) and a small amount (0.1% v/v) of a non-ionic surfactant (NC-200), containing 100% polyoxyethylene-alkyl- phenyl-ether. The process has been developed by analyzing the etching characteristics of (100) silicon wafers in pure and surfactant added TMAH.
Micro Electro Mechanical Systems, 2008. MEMS 2008. IEEE 21st International Conference on; 02/2008
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ABSTRACT: This paper reports the mechanical properties of silicon carbide (SiC) films at elevated temperatures up to 500degC. Poly-crystalline SiC film (poly-SiC) was deposited by LPCVD on a silicon wafer and patterned into a free-standing specimen on an "on-chip" tensile test device. The fracture strength of poly-SiC films showed little temperature dependence over the test temperature range. The tensile strength was 2.89 GPa at room temperature (RT), and decreased slightly to 2.66 GPa at 500degC. The fracture surface at 500degC showed almost the same morphology as that at RT, without any slippage. The potential of SiC films as a material for micromechanical devices working at high temperatures has been heretofore confirmed.
Micro Electro Mechanical Systems, 2008. MEMS 2008. IEEE 21st International Conference on; 02/2008
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ABSTRACT: In this work, we have developed a novel anisotropic wet etching process for the fabrication of MEMS microstructures with rounded concave and sharp convex corners, grooves for chip isolation, mesa structures with bent V-grooves, and 45deg mirrors by using a single etching mask. Tetra Methyl Ammonium Hydroxide (TMAH) at various concentrations with and without the non-ionic surfactant NC-200 at 0.1% of the total volume of the etchant has been used. In order to fabricate the microstructures with rounded concave corners, round shape mask pattern was used. Mesa structures and grooves for chip isolation were realized using spatially efficient convex corner compensation structures.
Micro-NanoMechatronics and Human Science, 2007. MHS '07. International Symposium on; 12/2007
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ABSTRACT: We have previously proposed an arrayed vertical motion system based on a tulip-shaped electrostatic clutch for producing haptic displays. The system has an advantage in that it is able to individually operate arrayed minute projection with high-power and large strokes (Output: 600 mN and displacement: 60 mum). This time, we added a new electrostatic latch mechanism to the system to individually control the projection state. We used MEMS technologies to fabricate a 4x4 array electrostatic latch mechanism. The total size of the mechanism was 6.0 x 6.0 x 0.5 mm. We evaluated the relationship between the applied voltage and a holding force of a few mN was obtained for the spring device.
Micro-NanoMechatronics and Human Science, 2007. MHS '07. International Symposium on; 12/2007
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ABSTRACT: We previously proposed a novel type of on-wall in-tube thermal flexible sensor, and confirmed that it can measure the flow-rate in both hydraulically developing and fully-developed conditions. This time, we investigated another outstanding advantage, i.e. the sensor is able to measure the flow-rate at axially asymmetric flow condition, and found that the sensor is applicable for the measurement of the flow-rate in bent tube condition.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: We have previously proposed a magnetic bead handling mechanism for micro-total-analysis-systems and have developed a palmtop-sized biochemical analysis system. Appropriate agitation is one of the crucial issues in micro-meter-sized fluidic systems. We investigated the agitation produced by using multilayered flat coils and magnetic beads. The beads were magnetically agitated inside the droplet by changing the external magnetic field distribution, and the agitation performance was evaluated by using an enzymatic reaction. The reaction efficiency increased linearly with an increase in the reaction time and was more than four times as efficient with agitation than without agitation.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: We have previously proposed an arrayed vertical motion system based on a tulip-shaped electrostatic clutch for producing haptic displays. The system has an advantage in that it is able to individually operate arrayed end-effecter elements with high-power and large strokes (output: 600 mN and displacement: 60 mum). We added a new electrostatic latch mechanism to the system to individually control the projection state. We used MEMS technologies to fabricate a 4times4 array electrostatic latch mechanism. The total size of the mechanism was 6.0 times 6.0 times 0.5 mm. We evaluated the relationship between the applied voltage and a holding force of a few mN was obtained for the spring device.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: We previously proposed an artificial hollow fiber, as a new MEMS material, for the development of a fabric tactile sensor. The artificial hollow fiber is fabricated by uniformly laminating metal and insulation layers onto the surface of an elastic hollow fiber. The fabric tactile sensor is made by weaving the modified hollow fibers into a cloth. The sensor can detect the contact force by measuring changes in capacitance at the points where the warp and weft fibers intersect, and can detect 2D contact force distribution by sequentially scanning the capacitance changes at all intersecting points. We investigated the dependence of sensor output on normal load and tension. The normal load and tension were independently applied to the fiber elements in order to determine the basic characteristics of the fabric sensor. We also developed two different glove-type wearable tactile sensors. One was made by patching the sensor onto an existing glove, and the other was made by directly weaving the hollow fibers into the yarn of the glove. In experiments with the patched sensor, we confirmed that it was able to detect contact force.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: This paper presents the mechanical properties of silicon-based membranes windows applied for miniature electron beam radiation system. The membranes were used for the physical separation between the vacuum and atmosphere, and used as an EB-permeable membrane window. We used MEMS technologies to fabricate the thin Si-based membrane window structure. The size of each window is 6 mm in length and 2 mm in width. Four different types of membrane windows were fabricated to compare the mechanical properties. Residential stress, Young's modulus, and breakage pressure were evaluated by using bulge test technique. SiN/SiO<sub>2</sub>/Si membrane showed the highest breakage pressure and operated more than one thousand hours.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: We developed a quasi-static tensile test system that controls environmental conditions, such as pressure, temperature, and surrounding gasses. Using this system, we evaluated the fracture properties of micron- and submicron-thick single-crystal-silicon film under several conditions. The strength of silicon measured in vacuum or helium was slightly higher than that in laboratory air. We measured the fracture toughness at different temperatures ranging from room temperature (RT) to 500degC and found a brittle-to-ductile transition at 70degC for micron-sized silicon film. The fracture toughness drastically increased at the transition temperature and saturated at a level of 2.5 MParadicm, which is twice the value at RT. On the other hand, submicron-thick silicon was less brittle: its fracture toughness was already 2.7 MParadicm at RT.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: In order to improve the reliability of Micro-electro-mechanical Systems (MEMS) designs, evaluations of the mechanical properties of soft magnetic materials are needed. In this paper, we present a tensile testing method to characterize the mechanical properties of microscale electroplated permalloy (80 wt% Ni, 20 wt% Fe) films. The gauge section of the specimen is 50 mum wide, 100 long and 5 mum thick. The measured Young's modulus of permalloy films is 113 GPa, and the tensile strength is 1.57 GPa. Both the properties are lower than those of thick permalloy films. The fracture strain measured by the images of specimens is about 2%.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: By applying a single rotary motion to our previously developed magnetic bead-droplet handling mechanism, we newly developed transportation and agitation operation mechanisms aiming at realizing a portable-sized biochemical analysis system. We used two permanent magnets for transporting beads and another magnet coupled with multi-layered flat coils for agitation. They are all mounted on a rotational table, and the total size of the system is 60 times45 times35 mm. We experimentally confirmed that the developed system can do all the beads' handlings (transportation, extraction, fusion, and agitation) by the rotational motion only.
Micro Electro Mechanical Systems, 2007. MEMS. IEEE 20th International Conference on; 02/2007
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ABSTRACT: We proposed an artificial hollow fiber structure as a new material for MEMS, and applied it for realizing a novel type of fabric tactile sensor. The hollow fiber structure is fabricated from commercially available silicone rubber tube by laminating a metal and an insulation layers on the surface. The fabricated hollow fiber is 250 mum in external diameter and 40 mum in thickness. The fabric tactile sensor is produced by weaving the hollow fibers like a cloth. Contact force on the sensor is detected by measuring the capacitance change at the intersection of two intersected fibers. The sensor detects the 2D contact-force distribution by sequentially scanning the capacitances at all fiber intersection points. The advantage of this novel fabric tactile sensor is that it can realize a genuine wearable sensor by directly weaving artificial fibers. In the present study, we fabricated artificial hollow fibers by thin-film deposition, and created a fabric tactile sensor by weaving the hollow fibers by hand. We confirmed the developed fabric tactile sensor can detect the contact force by measuring the capacitance change between the intersecting hollow fibers.
Micro Electro Mechanical Systems, 2007. MEMS. IEEE 20th International Conference on; 02/2007
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ABSTRACT: To improve the fidelity of the microinjection molding process, research is underway to implement silicon inserts as tooling surfaces in an injection molding machine. These tooling surfaces are created using typical microfabrication processes, such as bonding and chemical etching. The primary focus of this paper is the evaluation of anisotropic wet etching of off-axis silicon wafers, including experimental results and simulations. A method is presented for the determination of the lang110rang direction and subsequent alignment of the mask with an accuracy of 0.01deg. The use of atomistic kinetic Monte Carlo simulations reveals the extreme importance of proper alignment between the mask features and the off-axis wafer. As an example application, the fabrication steps and corresponding simulations of a silicon insert for the manufacture of disposable plastic razors are presented
Journal of Microelectromechanical Systems 01/2007; · 2.10 Impact Factor
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ABSTRACT: This paper presents that quartz tuning fork shows excellent properties as atomic force microscopy (AFM) probe. We used focused ion beam (FIB) system to monolithically form a sharp tip at the side end of one beam. The fabricated probe can vibrate and detect the deformation itself because of piezoelectric property of crystal quartz. We evaluated the vibration characteristic and the self-detection ability of tuning fork. The tuning fork probe is actuated in two different vibration mode; in-phase and anti-phase mode, and clarified that high Q-factor of 5247 was obtained in anti-phase mode. We further applied this mode for AFM observation and images were successfully with dynamic AFM system
Micro-NanoMechatronics and Human Science, 2006 International Symposium on; 12/2006
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ABSTRACT: This paper proposes an active tactile sensor driven by using piezo-electrical actuator. It consists of a silicon diaphragm having piezoresistive strain sensors for measuring displacement of the diaphragm, and a piezoelectric actuator for driving the sensing element. The proposed active tactile sensor has an advantage in that it can detect the multiple physical values, elasticity and impact resilience of a contact object, by analyzing the obtained step-response waveform. We fabricated the sensor element by using micro-electro-mechanical-systems (MEMS) technologies, and assembled it with a commercially available piezoelectric actuator in hybrid manners to produce the active tactile sensor. The sensor was 15 mm times 15 mm times 20 mm. Six different rubbers of different hardness ranging from A30 to A70 in Shore A, was used to evaluate the elasticity detection function of the sensor, and we confirmed that the output increased linearly with the increase in the rubber hardness (elasticity). We also evaluated two different rubber materials, urethane and damping rubbers, which had different values of impact resilience, and found that step responses of the sensor output were quite different between two (the damping rubber showed overshooting phenomena at the rise). We therefore concluded that the proposed sensor is capable of detecting two values, elasticity and impact resilience, of a contact object
Micro-NanoMechatronics and Human Science, 2006 International Symposium on; 12/2006
