Abstract-Electrostatic, comb-drive actuators have been designed for applications requiring displacements of up to 150 µm in less than 1 msec. A nonlinear model of the actuator relates the resonant frequency and the maximum stable deflection to the actuator dimensions. A suite of experiments that were carried out on DRIE, single-crystal silicon, comb-drive actuators confirm the validity of the model. Four actuator design improvements were implemented. First, a folded-flexure suspension consisting of two folded beams rather than four and a U-shaped shuttle allowed the actuator area to be cut in half without degrading its performance. Second, the comb teeth were designed with linearly increasing lengths to reduce side instability by a factor of two. Third, the folded-flexure suspensions were fabricated in an initially bent configuration, improving the suspension stiffness ratio and reducing side instability by an additional factor of 30. Finally, additional actuation range was achieved using a launch and capture actuation scheme in which the actuator was allowed to swing backward after full forward deflection; the shuttle was captured and held using the backs of the comb banks as high-force, parallel-plate actuators.

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Thermal actuation of integrated valve structures is attractive due to the relative simplicity of the actuator design, the moderate activation time possible, the relatively low total power required, and the ability to fully integrate the actuator with the flow control component. Of the many thermal actuation schemes, the use of bimetallic elements is preferred, particularly when a low cost, fully integrated structure is desired. Bimetallic structures allow both normally-open and normally-closed valves by varying the boundary conditions at the support for the actuator, which is difficult to achieve with many alternate technologies. One such valve has been designed to provide fully proportional control of flows in the range of 0-150 cc min-1 at input pressures between 1 and 50 PSIG. The valves are batch fabricated using silicon micromachining techniques. By combining these valves with pressure or flow sensing elements, closed loop pressure or flow control is easily accomplished.

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