We have developed a microreactor for Polymerase Chain Reaction (PCR) by means of microfabrication technologies. The microreactor has been constructed to amplify DNAs, which was much faster than a conventional apparatus. Its size was 30×16mm, in which a reaction chamber with 10mm square and 300 μm depth was constracted. It was found that this microreactor requires only 20 minutes to perform 40 cycles of a shuttle PCR, 3 times faster than conventional apparatus.

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Dielectrophoresis (DEP) refers to the motion of particles that results from the interaction between a non-uniform external field and the induced dipole moment. Under an extremely high field-gradient created in microfabricated electrode systems, objects with molecular dimensions, such as DNA, can be attracted and trapped. Since the DEP force is stronger for large objects, biomolecules can be separated by the difference in their molecular size. In this paper, the electric field-flow separator, which we call DEP chromatography, is developed and tested. The device consists of a microelectrode array for dielectrophoretic trapping of biomolecules, which is covered by a lid having a microfabricated fluid passage. Water solutions of λ-DNA (48.5kbp) and an oligonucleotide (22 nucleotides) are fed to the device, separately or as a mixture. Under the field strength of 1MV/m at IMHz, λ-DNA is collected onto the electrode array, while the oligonucleotide is not, thus enabling the separation between λ-DNA and the oligonucleotide. During the experiment, dependence of the DEP collection on the molecular concentration is observed. The interpretation for this phenomenon is the aggregate formation at high molecular concentrations due to the attractive force between induced dipole moments on the molecules.

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We have examined the LIGA process for the microfabrication of capillary array electrophoresis (CAE) chip using synchrotron radiation lithography in polymethylmethacrylate (PMMA) substrates and developed novel type microfabricated CAE chip. Laser-induced fluorescence detection system for the CAE chip has been constructed by the modification of laser confocal fluorescence microscopy. DNA molecules labeled by intercalating fluorescent dye were detected during migrating in the array of microchannels and conformational dynamics of single DNA molecule in microchannels filled with linear polyacrylamide under electric field was observed by this system to elucidate the separation mechanism of DNA and to optimize the separation conditions for DNA analysis. Based on this observation, we demonstrated that linear polyacrylamide is suitable for the rapid separation of large DNA fragments less than 166 kbp by microfabricated CAE chip without pulsed electric field.

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We have developed a new method for cleaning flow-through cells by using microbubbles and ultrasonic (US) standing waves. A standing wave generated by US transducers at 1 MHz was used to trap microbubbles at node positions of the sound pressure. We were also able to control the microbubbles' positions spatially through frequency modulation. We found that these microbubbles were very effective for washing microbeads out of flow-through cells, particularly when frequency-modulated US irradiation was used. The proposed method promises to be very useful for cleaning the flow-through cells in small analytical instruments.

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To realize integrated multi-step Micro Total Analysis Systems (μTAS), pneumatic manipulation of reagent droplets is a promising scheme. In this scheme, passive vent valves are required for positioning and mixing of the droplets. This paper presents a novel microstructure named Hydrophobic Microcapillary Vent (HMCV). An array of hydrophobic microcapillaries allows air passing through it, whereas it stops liquid by negative capillary action. Test structures have been fabricated by molding technique of silicone elastomer. Positioning and mixing functions of droplets with pL-nL volume are demonstrated.

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Microchips for capillary electrophoresis have been fabricated in small size on quartz glass substrates. Microchannels with smooth sidewalls are etched by applying adopted etching condition. To fabricate quartz glass chips, we applied a novel bonding method with dilute hydrofluoric acid solution. Using fabricated microchips, we show that they permit to perform quantitative sample injection (several 10pl or less), effective separation (the number of theoretical plates is over 2, 500) and high speed analysis (_??_30 sec). In order to improve the detection sensotivity of UV absorbance method, we have developped the chips which have optical slit, and confirmed that the absorbance unit was improved about ten times.

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A concept of new micro capillary array chip for DNA analysis was proposed and it was fabricated by deep X-ray lithography technology. The chip was made of PMMA and it contains 20 micro channels with width of 50μm, depth of 100μm and space between channels of 10 to 50μm. As an technique to control an inclination angle of a micro channel side wall, a newly developed moving mask LIGA (M²LIGA) technology was proposed. The side wall inclination angle was successfully controlled between 90 to 70 degree by varying a diameter of a mask movement.

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Advanced micro sensors for ultrasonic imaging, pressure, acceleration, angular rate and atomic force have been realized based on silicon bulk-micromachining. Novel techniques as deep Reactive Ion Etching (RIE), XeF₂ silicon etching have been developed for precise micromachining and applied for the sensors. The deep RIE of silicon has been applied for electrostatic microactuators. Parallel electrodes in a packaged glasssilicon structure enable electrostatic force balancing servo sensors, resonant sensors and electrostatically levitating micromotors. Nano-machining based on the Scanning Tunneling Microscopy (STM) technology have been also developed to fabricate extremely small structures.

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It is well known that the human auditory system has acute sensitivity to AM-FM components of sounds. We are aiming to obtain an appropriate structure and algorithm underlying this, and realize it as an imbedded function of future auditory sensors. In this paper, we introduce a logarithmic differential decomposition of subband signals into basis waveforms, and show 1) AM and FM are expressed as a real part and an imaginary part of these signals, 2) the basis waveform is uniquely characterized by the corresponding zero, 3) the basis waveforms are asymptotically orthogonal each other, and hence, 4)the zeros sequence can be optimally extracted using the matched filtering of the AM-FM components by the basis waveform.

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A new amperometric mode of operation of bipolar magnetotransistor (AMOBMT) is studied both theoretically and experimentally. This mode is achieved without reverse-biasing of the collector junctions and by using the current between the two ‘floating’ collectors as an information signal. The output current is a linear and anti-symmetrical function of the applied magnetic field. AMOBMT has some advantages with respect to the conventional mode of operation of bipolar magnetotransistor which utilizes reverse-biasing of the collector junctions.

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