Studies on micro flow sensor for ultra high speed flow and ultra low speed flow

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The results of our studies are listed below.1. Fabrication of wing type micro flow sensors for ultra high speed flow measurementsRectangular wing supported by 4 fine beams located in a microchannel was designed. The micro structures were fabricated using selective etching method of the highly boron doped p+ layr and Si-to-glass anodic bonding method. The sensor consists of 4 wafers of glass-Si-Si-glass and the micro channel was formed in the 2 Si wafers. The displacement of the wing caused by the lift force under gas flow is measured by the laser interferometric displacement sensor. Many types of wing having different sizes of the chord, length etc.was fabricated and tested. The aspect ratio, ratio between the length and the chord, is important for characterization of the sensor. The relationship between the displacement and flow speed was measured using compressed air as the gas flow. The wing having high aspect ratio shows high sensitivity. The residual stress, however, reduce the sensitivity of the sensor. We are going to improve the structure and fabrication process.2. Design of thermal micro flow sensor for ultra low speed flow measurementMicro flow sensor consists of two micro resistor heater/thermal sensor having very small thermal copacitance was designed. It is now on fabrication using the same methods of wing type micro flow sensor.3. Characterization of fluidics in microchannelVarious kinds of micro channels were fabricated and their flow characteristics were measured. The results were very useful for the designing of micro flow devices and micro total analysis systems.4. Low temperature anodic bonding methodTo reduce the residual stress coused by the anodic bonding, anodic bonding using lithium-aluminosilicate glass-ceramic was studied. The bonding tenperature can be reduced to 60C (conventionally 400C) with the glass ceramic. The bonding method is also very useful for packaging of the microsensors and the assemblying of the micro total analysis systems.