A new type of silicon MEMS valve array for micro-fluidic control is described. The device consists of parallel arrays of electrostatically actuated, bi-stable mechanical micro-valves for precision flow control. Five characteristics make these micro-fluidic systems unique. First, they consist of large numbers of simple valves, working cooperatively to achieve precise linear control of flow. Second, they operate using low power, binary electrostatic actuation. Third, they are designed for use in either gases or liquids. Fourth, they are fabricated using conventional silicon micro-machining processes. And finally, they are inherently scalable over a wide range of precision levels and flow rates. Devices were fabricated with 5 micron gaps between the actuator and underlying substrate, with three different actuator sizes — 300 by 300 microns, 400 by 400 microns and 500 by 500 microns. Air-flow tests on fabricated 25-element-array devices have demonstrated the linear relationship between flow rate and number of valves open, indicating flow rates per valve as high as 5.7 ml/min at 10 kPa pressure. The experiments also revealed the strong coupling between the fluid mechanics and mechanical behavior of the valve. An incompressible, continuum-based flow model was developed using lubrication theory. The model was capable of capturing the effects of actuator deflections as large as 5 microns, and predicting flow rates within 10 percent over a range of pressure differentials from 2 to 18 kPa.

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