Effects of the Temperature-Dependent Behavior of the Gap-Filling PDMS on the Response of a Capacitive MEMS to the Electrostatic Actuation

In recent years, researchers have shown interest in using elastomers with high dielectric constant and good elasticity in capacitive MEMS. This paper aims to investigate how the performance of capacitive sensors/actuators is affected by the temperature-dependent behavior of gap-filling Polydimethylsiloxane (PDMS). As a case study, a model is created, consisting of a proof mass with two attached flexible microbeams parallel to a stationary electrode, under electrostatic actuation. The actuation is directly proportional to the temperature-dependent dielectric constant. To reduce resistance stiffness, the bulk PDMS was assumed to have porosity, resulting in a nonlinear displacement-dependent Young’s modulus. The system’s static and dynamic responses were obtained by solving the governing nonlinear equations using Galerkin-based numerical procedures. Additionally, a physically gradient-descent-based learning method was used to predict the nonlinear frequency response of the system. The results have shown that using PDMS instead of an air gap significantly reduces the required actuation voltage, although this difference is less pronounced at higher temperatures. In addition, the inclusion of PDMS alters the resonance behavior of the system and also reducing the temperature diminishes the nonlinear softening behavior of the system under specific bias and AC voltages.