ELECTROSTATIC CURVED ELECTRODE ACTUATORS

This paper presents the design and performance of an electrostatic act uator consisting of a laterally compliant cantilever beam and a fixed curved electrode, both suspended above a ground plane, A theoretical d escription of the static behavior of the cantilever as it is pulled in to contact with the rigid fixed-electrode structure is given, Two mode ls are presented: a simplified semi-analytical model based on energy m ethods, and fully three-dimensional (3-D) coupled electromechanical nu merical simulations using CoSolve-EM, The two models are in qualitativ e agreement with each other, and predict stable actuator behavior when the beam deflection becomes constrained by the curved electrode geome try before electrostatic pull-in can occur, The pull-in behavior depen ds on the shape of the curved electrode, Test devices have been fabric ated by polysilicon surface micromachining techniques, Experimental re sults confirm the basic theoretical results, Stable behavior with rela tively large displacements and forces can be generated by these curved electrode actuators, Depending on the design, or as a result of geome trical imperfections, regions of unstable (pull-in) deflection behavio r are also observed.