Piezoelectric ultrasonic microsensors have been fabricated on buckling-controlled silicon dioxide diaphragms for sensitivity enhancement. A precise stress control process has been developed for fragile SiO₂ diaphragms, which are derived from a surface oxidized normal silicon wafer, to allow spontaneous buckling and to make re-buckle upward. The fabricated sensors on upward- and downward-buckled SiO₂ diaphragms have been evaluated in terms of static deflection and sensitivity. The upward-buckled diaphragms show the deflection around +4.8μm while the downward ones show that around -3.5μm. Totally a four times higher sensitivity is obtained on average of forty sensors in the comparison of the upward diaphragm sensors to the downward ones.

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In the emerging fields related to healthcare, energy, and environment, realization of devices on flexible sheets is imminent. The materialization of such sheets would require fabrication of parts of devices on a fiber substrate where they can be assembled and interconnected by weaving. To broaden the area of a flexible sheet device, larger number of such devices will need to be formed directly on the fibers. Moreover, fabrication cost of a flexible sheet device, larger number of such devices will have to be addressed in order to make large size fabric manufacturable at affordable price. Therefore, a high-speed, low-cost, environmental friendly batch-manufacturing process of the devices on fiber is required. In this paper, we developed a reel-to-reel thermal imprint system combined with a sliding roller imprint mechanism. In this process, fiber substrate is sandwiched by a couple of flat molds, and these molds slide opposite direction each other under suitable press force and temperature. And then, we optimized conditions of this imprint process. Finally, we succeeded to imprint continuously more than 100 times and to fabricate 1.6 m long imprinted fiber. And we succeeded to imprint almost on entire cylindrical surface. A stable imprinted region was about 160° at each side.

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The MEMS thin film heater was prepared by all dry processes and the heating properties of this heater were evaluated. The MEMS heaters were heated up to 400°C at consumed power of a few ten mW. The consumed power for heating was dependent on the heater area and the membrane size. Furthermore, 40 ppm ethanol gas was detected in smaller size and at lower-power consumption by the MEMS gas sensor utilizing this MEMS heater than by the conventional bulk gas sensor.

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A novel sealing technique using sacrificial microchannels was proposed for atmosphere control in a micromachined alkali gas-filled cell for a chip scale atomic magnetometer. The microchannels act as feedthrough connecting the cell to outside atmosphere during evacuation and gas-filling steps, and eventually they are sealed by glass-frit reflow. Si microchannel dedicated as a sacrificial microchannel was proposed and its feasibility was successfully demonstrated by experiments. The simulation results clarified the glass-frit reflow characteristics and its dependence on cross-sectional shape of the microchannel. Hermeticity of the proposed sealing technique of less than 10^-12Pa·m³/s leak rate was verified by a high resolution helium leak test.

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This paper reports the theoretical and experimental investigations of the strain sensitive effect of a 2-D photonic crystal (PhC) cavity for strain sensing applications. Strain sensitivity of a high quality factor PhC cavity is studied based on finite element method (FEM) and finite difference time domain (FDTD) simulations. The results show that the resonant wavelength of cavity is proportional to the application of strain. Linear relationships between strain applied and shift of resonant wavelength were obtained. Thus, it is possible to detect the strain by determining resonant wavelength shift. The test device was fabricated using micromachining for experimental investigation. The sensitivity to longitudinal strains was determined to be 0. 95 pm/μ-strain.

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We report on a novel MEMS (Micro Electro Mechanical Systems) based Fabry-Perot spectrometer with ultra wide wavelength range (3.2-8.4 μm) compared to the previously reported ones (typically 2.8-5.8 μm). The wavelength range of a Fabry-Perot spectrometer is known to increase by increasing the ratio of the refractive indexes of the multilayer mirrors. Thus, a novel mirror structure was proposed replacing low refractive index layer of SiO₂ (n_L=1.44) by “air (n_L=1)” for wider wavelength range. The proposed device was fabricated by HF sacrificial layer etching of SiO₂ between four ultra-thin polysilicon films (ca. 320 nm). The following two ideas were adopted to fabricate this delicate structure properly. (1) Electrostatic force was generated only in the outer region surrounding the air mirror not to deform the mirror. (2) Supercritical drying process was employed after the sacrificial etching to prevent the possible sticking issue.

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A modeling method for piezoresitive nanocantilevers using their geometrical parameters is described. The spring constant and the effective mass of piezoresistive nanocantilevers are formulated using theoretical and approximation equations, which shows a good agreement with the results of finite element analysis. The displacement sensitivity and minmum detectable force of piezoresistive nanocantilevers with non-uniform doping profiles are calculated by introducing a piezoresistive efficiency factor.

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