Paper MN-TuM12
Theoretical and Experimental Investigation of Electrostatically Actuated Bistable Micro and Nano Structures

Tuesday, October 21, 2008, 11:40 am, Room 206

In this work, theoretical and experimental study of initially curved electrostatically actuated micro and nanobeams with clamped ends was performed. Due to unique combination of non-monotonous stiffness-deflection dependence typical for mechanically bistable structures and of nonlinear electrostatic force abundant in micro and nano systems the structure exhibits sequential snap-through buckling and electrostatic pull-in instability as well as multiple stable configurations at the same voltage (bistability). Reduced order Galerkin and consistently constructed lumped models were built and verified by numerical analysis and experimentally. The minimal initial elevation required for appearance of the bistability in the electrostatically actuated beam is smaller than in the case of an uniform deflection independent loading; closed form approximation of this elevation was evaluated. The devices were fabricated from silicon on insulator (SOI) wafer using deep reactive ion etching and in-plane responses were characterized by means of optical and Scanning Electron microscopy (SEM). In addition, out-of-plane moving nano scale devices made of a intrinsically pre-stressed polysilicon were fabricated and characterized. Characterization inside a SEM was found to be a useful experimental approach providing stable operational in-vacuo conditions while higher magnification improves the quality of data processing. Model results obtained for the actual dimensions of the device were in good agreement with the experimental data. Designs incorporating bistable beams have clear functional advantages and may result in improved performance of switches, capacitive based sensors and MEMS/NEMS based nonvolatile memory devices.