Synthesis of Electro-Statically Actuated MEMS
This chapter presents a synthesis methodology for electrostatically driven microelectromechanical systems. It addresses issues of simulation, sensitivity analysis and optimization. As an application of the general methodology, design of variable gap comb drives (shape motors) is presented. Direct simulation of the electrostatic field is carried out by the exterior, indirect boundary element method and shape sensitivities are obtained by the direct differentiation approach. The inverse problem determines the shapes of fingers of a comb drive such that the driving force is a desired function of its travel distance. Commercially available optimization codes are used to solve the synthesis problems. Numerical results are presented for shape motors that produce linear, quadratic or cubic force profiles. Based on the design, a cubic motor was fabricated using the SCREAM process. The driving forces were measured and the results were compared with the theoretical predictions.
KeywordsDesign Variable Boundary Element Method Finite Difference Method Moving Finger Force Profile
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