Hierarchy of models for electrostatic comb-drive actuators in electrolytes

Abstract

Electrostatic comb-drive actuators in electrolytes have many potential applications, the most popular of which is characterizing the mechanical properties of biological structures at small scales. Maximizing the utility of these devices for such applications requires a model capable of accurately predicting their behavior. The current state of the art model of these actuators assumes (i) that the native oxide is a pure dielectric, (ii) that the ion concentration of the bulk electrolyte is constant, and (iii) that the Stern layer can be neglected compared to the oxide layer. This model captures the general behavior of the electrostatic actuator in electrolytes, but has limited accuracy. We propose a hierarchy of models that addresses the suitability of these assumptions separately and in concert. We find that the model which removes assumptions (i) and (ii) is sufficient to accurately predict the displacement of a comb-drive actuator in electrolytes.