Closed-Form Model for Laterally Driven Electrostatic Combs With or Without Overlap

Abstract

This letter presents a closed-form model for laterally-driven electrostatic combs with zero or negative overlap (disengaged combs). In this case, capacitance is determined by the fringing fields between the tips of the fingers, resulting in a complex dependence on position and on the ratio of finger width to gap. We propose a single analytical formula which accurately captures these effects for a wide range of geometries and is valid in the better-known large overlap case. Our model relies on conformal mapping techniques. We first derive an analytical formula in the case of comb fingers with infinitesimal width compared to the gap. This formula is then adjusted to account for finite finger width by fitting with numerical simulations. The resulting model is validated through a comparison to experimental measurements taken from literature. [2026-0045]