Fabrication and characterization of a micromachined passive valve

This paper describes the structure, fabrication and detailed characterization of a polycrystalline silicon passive microvalve. The microvalves were fabricated utilizing micromachining techniques, and automated measurement systems were developed for device characterization. The valves were successfully characterized to determine the effect of dimensions on fluid flow rate and valve deflection. Methanol, deionized water and nitrogen were used for fluid flow tests, and nitrogen gas was used in the deflection measurements. The ratio of reverse to forward flow rates of methanol was found to be less than 3% at a pressure of 11 kPa. The measured data are in good agreement with a first-order model for the device taking into account applied pressure, valve plate deflection and the resistance of the inlet hole. Using nitrogen gas, analysis of the device was extended to measure the valve plate deflection as a function of inlet pressure. Valve plate deflections of up to 15.3 mum were recorded at 31 kPa. The nitrogen gas flow characteristics differ significantly from the liquid flow characteristics due to the compressible nature of the fluid, but agree well with the theoretical flow for gases.