Design and analysis of planar and lattice electrostatic comb drive actuators

Abstract

This paper presents an analysis of the electrostatic forces that act on a laterally driven comb drive actuator, in order to provide a clear understanding of the actuator geometry and its effects on system performance. Contrary to more familiar models, we provide a proper breakdown of the forces acting on a lateral comb drive structure by examining the electric field induced in a single actuator finger. Our results demonstrate the asymmetric nature of the forces, and its consequences. To counter these effects, we propose a novel actuator design which employs an out-of-plane interdigitated comb lattice. The simulation results comparing the new lattice design to the traditional planar comb drive actuator reveal a 66% increase in lateral actuation force, a 40% increase in change in capacitance per unit displacement, in addition to superior rectilinear stability under torsional forces.