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Many studies have been reported relating solar cells and MEMS technology. There are two different categories of the topics. One is introducing MEMS fabrication technique to the solar cells for the miniaturization or the higher performance. Another is building a new device or system using the solar cell as the energy source for the autonomous microsystems.

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The studies on micro thermoelectric generators are reviewed in the present paper. The configuration of the devices is introduced for understanding the mechanism of thermoelectric generators. The fabrication processes and the output power of the micro thermoelectric generators are discussed. Finally, the micro-thermoelectric devices using nano-structured materials are introduced to understand the effects of thermoelectric properties on the device performance.

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Electrical power generation from carbohydrates produced by living systems is one of attractive green energy technologies, and has motivated for decades the development of enzymatic biofuel cells (eBFC) that can directly generate electricity without purification of the biofluids. In this review, we explain resent progress of enzymatic power generation in-vitro and in-vivo, and then describe the perspective of eBFC system with particular emphasis on the performance and stability requirements toward medical applications.

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The study on vibration-driven micro generators was discussed. Typical vibrations around us were shown and some ideas of micro generators based on the vibrations were introduced. Advantages and disadvantages of electrostatic induction generators and electromagnetic generators were described. After that, the difference between electret generator and piezoelectric generator, although these two categories are belonging to electrostatic induction generators, were discussed. Finally some examples of electrostatic induction micro generators were shown.

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In this paper, dimension optimization of supporting portion was carried out for an originally designed high-frequency fundamental AT-cut quartz resonator, which has a firstly applied peripheral electrode and 10-µm-thin vibration portion to generate above 150 MHz fundamental thickness-shear vibration. Using three-dimensional finite element modeling, it is the first time; dimensions of supporting portion were optimized through improving energy trapping and reducing vibration couplings. Based on optimization results, resonators with different dimensions were fabricated and their Q-factors were measured. The experimental results were very consistent with the optimization results. Improvement of the resonator's performance ensured the validation of our method.

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Compact optical gas sensors based on the Raman effect and ultraviolet absorption spectroscopy were developed. These sensors are miniaturized and do not require alignment, because the mirrors and optics are fixed onto a precisely machined micro optical bench made by micromachining technology. The Raman type gas sensor consists of a small DPSS laser (wavelength 532 nm, pulse energy 200 µJ, pulse width 3 ns, repetition frequency 1 kHz), the sensor chip, and the detector, which are connected by optical fibers. The UV absorption type gas sensor is consists of a D₂ lamp, the sensor chip and a compact spectrometer, which are connected by optical fibers. The measured signals showed good linearity along with the gas concentrations. The limit of detection using the Raman effect was 1% for hydrogen or 0.2% for methane, and the minimum limit of detection using ultraviolet absorption spectroscopy was 10 ppm for ammonia and sulfur dioxide for an optical path length of 20 mm.

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In this research we fabricated a thermionic power generator with 10 µm gap. The thermionic power generator has an emitter and a collector. The emitter and the collector are separated with the gap via insulation spacers. A Si wafer coated by a W thin film was used as the emitter, and a Pt-coated Si wafer was used as the collector substrate. The thermionic power generator placed in a vacuum chamber, Cs gas was introduced to the chamber to enhance emission and its output characteristics are evaluated. When the emitter with an area of 25 mm² is heated to about 980°C by lamp heater, and temperature of the collector increases at 440°C. A maximum output of about 1.3 mW is obtained when a load resistance of 11.1 Ω is connected to the output terminal. The theoretical output of this thermionic power generator is calculated to be about 2 W. The experimental efficiency of the thermionic power generator is about 0.01%.

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Minimal Fab System Photolithography has been developed for wafer patterning process without the requirement of a cleanroom. It consists of minimal resist coater, minimal maskless UV exposure, minimal mask aligner and minimal resist developer. We have proved in practice that the spin coating using minimal resist coater for a 0.5-inch wafer gives the identical result of resist thickness compared with 4-inch wafers without changes to a higher rotational speed. The minimal maskless UV exposure using Digital Light Processing (DLP) confirms that only one LED light source with the light intensity of 150 mW/cm² can expose over a 0.5-inch wafer in a few minutes. The minimal mask aligner is developed for a high speed exposure within 5-20 seconds. The aligner also uses a LED light source that can produce the light intensity of 14 mW/cm². The present photoresist resolution for the maskless UV exposure and the mask aligner are 1 µm and 2 µm, respectively. The minimal developer has minimized its consumption of developing agents. Due to the surface tension, a volume of developing agent is kept on the wafer surface for slowly spinning to stimulate the developing process. The developing time is 20% saved from that of the conventional puddle development.

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To minimize the damage caused by slope failure, knowledge of the increase in water content in mountain soil is important; however the current technology for monitoring this is insufficient. In this study, an EC sensor chip with an insulation layer with increased thickness, designed to reduce leakage current, was fabricated. Utilizing the chip, a wireless sensor terminal was constructed for long term continuous monitoring of the water content in mountain soil. The usefulness of the EC sensor for predicting slope failure was confirmed.

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