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11 July 2002 Vertical electrostatic actuator with extended digital range via tailored topology
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We describe the design, fabrication, and testing of an electrostatic vertical actuator that exhibits a range of motion that covers the entire initial gap between the actuator and substrate and provides controllable digital output motion. This is obtained by spatially tailoring the electrode arrangement and the stiffness characteristics of the microstructure to control the voltage-deflection characteristics. The concept is based on the electrostatic pull down of bimaterial beams, via a series of electrodes attached to the beams by flexures with tailored stiffness characteristics. The range of travel of the actuator is defined by the post-release deformed shape of the bilayer beams, and can be controlled by a post-release heat-treat process combined with a tailored actuator topology (material distribution and geometry, including spatial geometrical patterning of the individual layers of the bilayer beams). Not only does this allow an increase in the range of travel to cover the entire initial gap, but it also permits digital control of the tip of the actuator which can be designed to yield linear displacement - pull in step characteristics. We fabricated these actuators using the MUMPs surface micromachining process, and packaged them in-house. We measured, using an interferometric microscope, full field deformed shapes of the actuator at each pull in step. The measurements compare well with companion simulation results, both qualitatively and quantitatively.
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Yanhang Zhang and Martin L. Dunn "Vertical electrostatic actuator with extended digital range via tailored topology", Proc. SPIE 4700, Smart Structures and Materials 2002: Smart Electronics, MEMS, and Nanotechnology, (11 July 2002);

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