Fluid-powered rotary gears and micro-flow channels

Micromechanical rotary gear trains and single rotors have been made from polysilicon and silicon nitride using surface micromachining techniques. The gear diameters range from 60 to 1600 mu m. The movable structures have been integrated with selectively encapsulated surface-micromachined flow channels and on-wafer gaskets, making it possible to use fluidic actuation as the driving force for flowmeters and gear trains. This selective encapsulation is achieved in the course of microstructure fabrication and is not a subsequent capping or wafer bonding process. The authors have demonstrated long-term actuation of a single rotor operated at 3750 rpm, obtaining over 4 million continuous rotations in a 19-hour test. The rotor motion was detected optically, using an inexpensive phototransistor. Fluid actuation combined with optical detection results in a system useful for hazardous environments where high voltages or electrical leakages cannot be tolerated.<
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