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For on-site evaluation of the quality of foods, microdevices are very attractive. We have particularly focused on the development of devices directed to the diagnosis of bovine subclinical mastitis and freshness of foods. Electrochemical techniques are useful for this purpose. Also, novel microfluidic techniques have been developed to facilitate processing of solutions. Recent progress of our researches on devices directed to food analysis will be introduced.

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This paper shows the fabrication of a fluidic device for measuring of membrane potential changes of multiple cells. The device is composed of poly(methyl methacrylate) (PMMA) and a silicon substrate that has needle-shaped structures for electrodes. The electrodes are for “two-electrode voltage clamping method” that can measure ion flows across cell membrane using an amplifier and two electrodes inserted into a cell. In this device, Xenopus laevis oocytes can be arrayed automatically in the fluidic channel and penetrated by electrode structures at the same time. To construct the fluidic device integrated with electrodes, we simulated and calculated the fluid behavior for oocytes array and investigated the flow rate for electrodes insertion into oocytes.

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In this study, we propose a simple observation method of the shape and molecular orientation of the chromosomes extracted from cells for a sample-to-analysis system in clinical diagnosis. The proposed technique is composed of total preparation technique such as cell immobilization, chromosomes extraction, stretching, suspension and analysis using a disposable microchip controlled by centrifugal force only. It is experimentally confirmed that the chip having two kinds of microstructures arranged concentrically on a chip immobilizes cells and stretches chromosomes extracted from the immobilized cells.

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A measurement method of surface texture of objects using active touching of a tactile sensor which has inclined micro-cantilevers with strain gauge film on Si has been reviewed. The fabricated tactile sensors have an ability of detecting roughness of more than ∼20μm, and they can detect striped pattern on the Japanese banknote. Various kinds of blank paper which have different properties including hardness, friction coefficient, and surface roughness were identified using output from the fabricated tactile sensor. The feature quantities which depend on paper properties were defined from the resistance change by pushing, moving, and stopping of the sensor. The papers were classified in four clusters by principal component analysis of defined feature quantities.

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This paper presents a novel QCM (quartz crystal microbalance) sensor for detecting interactions between membrane proteins and their ligands using liposomes derived from human cells. First, liposomes having BCR (B-cell receptor) were derived directly from cell membranes by stimulating human lymphocyte cells, Ramos, with NaB (sodium butyrate). Next, the liposomes were separated from the cells by filtration and micronized by sonication. Then, the liposomes were immobilized on the surface of a QCM sensor chip using cell-anchoring molecules. Several experiments demonstrated that ligand detection is achieved by frequency reduction with application of the antibody against BCR.

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Particulate contamination on a wafer is the most crucial problem for wafer bonding, which is one of key process technologies for MEMS (Micro Electro Mechanical Systems). To address the problem, physical assists such as megasonic agitation is generally employed, but acoustic agitation often causes damage to fragile MEMS structures. In this study, several cleaning methods were compared in terms of both particle removal efficiency (PRE) and damage to the fragile MEMS structures. Conventional immersion type cleaning or ultrasonic cleaning cannot remove small particles efficiently, while atomized water jet spray (2-fluid jet spray) cleaning with pressurized nitrogen gas can effectively remove particles without damage to cantilever structures in a short time. Megasonic cleaning with de-ionized water can remove the particles, but it damages the cantilever structures at a same time. In contrast, megasonic cleaning with surfactant dissolved water or diluted ammonia/H₂O₂ water can effectively remove particles even at a low physical energy, which causes no damage to the structures.

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Local ambient gas control technologies for atmospheric pressure plasma processes using a new curtain gas structure have been developed. The local ambient gas control was studied theoretically and experimentally. Safe and clean process conditions (reactive gas leakage below 0.1 vol.% and air contamination below 10ppm) were achieved in open air. H₂ plasma was generated with H₂ concentrations above the explosive limit (4.1% in air) successfully. As an application, Cu reduction and SiO₂ etching were demonstrated. These results indicate that our local ambient gas control technologies have adequate potential for atmospheric pressure plasma processes.

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In this paper, we propose a high-accuracy spray coating method for obtaining the thick photoresist over 200μm. A multi-layered coating method with thin photoresist layers is applied in order to achieve a thick photoresist. We evaluated the waviness and the reproducibility of the thickness of the photoresist coated on a flat substrate. The multi-layered spray coating method with the edge cover achieves high accuracy thickness of the photoresist with covering wide-range of the target thickness.

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