Radio-frequency microelectromechanical systems (RF MEMS) are widely used for contact actuators and capacitative switches, and involve metal-dielectric contact. Proper understanding of structure-electrostatics interaction is necessary to prevent failure of these systems. In these devices, the structure is activated by an electrostatic force, whose magnitude changes as the gap closes. Accurate modeling of fluid-structure-electrostatics interaction is important to determine device dynamical behavior, and ultimately, device lifetime. It is advantageous to model fluid and structural mechanics and electrostatics within a single comprehensive numerical framework to facilitate coupling between them. In this paper, we extend a cell-based finite volume approach popularly used to simulate fluid flow to characterize structure-electrostatics interactions. The method employs fully-implicit second order finite volume discretization of the integral conservation equations governing elastic solid mechanics and electrostatics, and uses arbitrary convex polyhedral meshes. The electrostatic actuation is treated as a surface force, and is directly added to the force balance for the control volume. The resulting set of algebraic equations is solved using a biconjugate gradient stabilized (BCGSTAB) solver. Results are presented in this paper for a fixed-fixed beam under electrostatic actuation.
Low voltage RF MEMS variable capacitor with linear C-V response