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8 January 2007 Investigation of vertical displacement thermal actuators
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In this paper, we present design, modeling, fabrication, testing techniques and experimental verification for a bi-directional thermal actuator. The actuation principle is based on the asymmetrical thermal expansion of pseudo-bimorph microstructures due to the difference in the electrical resistance of two stacked poly-silicon layers. Bi-directional actuation is achieved depending upon the application of currents on either the top or bottom layers. Various designs were fabricated using the commercial foundry process PolyMUMPS and characterized with a reflective microscope and an optical profiler. Previous demonstrated designs had a limited vertical displacement due to the mechanical limitation imposed by the flexural lengths of the actuator arms. We proposed a new design allowing an increase of the maximum displacement by 85% with the same input voltage of 7V. The flexure arm is incorporated in the top silicon layer such that the torsion forces on the flexural arms are minimized. This enables larger deflection of the actuator arm without significant increase in the temperature. Different device configurations have been designed and tested. The temperature distributions on the actuator arms and displacements of the actuators at various conditions were analyzed using finite-element analysis and verified experimentally. We will discuss the design configuration, testing techniques and practical issues. The potential applications of the out-of-plane actuators include flow sensors, variable capacitors, resistive sensors, optical switches and RF switches.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Naresh Dhaubanjar, Smitha M. N. Rao, Hsu Lun-Chen, Matthew Luquire, Dan Popa, Mu Chiao, Harry Stephanou, and J.- C. Chiao "Investigation of vertical displacement thermal actuators", Proc. SPIE 6414, Smart Structures, Devices, and Systems III, 641420 (8 January 2007);

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