Dynamic response of MEMS sensor near fundamental and higher-order frequencies

We present a theoretical and experimental investigations into the dynamic response of initially curved microbeams (arches) near their fundamental as well as higher-order frequencies. A reduced-order model based on a nonlinear Euler-Bernoulli beam model is utilized. The model accounts for the electrostatic bias on the microbeam and its geometric nonlinearities (mid-plane stretching and initial curvature). Simulation results are presented showing the combined effect of the nonlinear electrostatic force and the initial curvature in triggering the so-called snap-through instability of the investigated microbeams. For the experimental part, two micromachined initally curved beams made of polysilicon were subjected to DC and AC harmonic loads. Several experimental data are shown demonstrating softening and hardening behaviors of the considered structures near their first and third natural frequencies, respectively, as well as a possible dynamic snap-through motion.