An experimental study for characterization of size-dependence in microstructures via electrostatic pull-in instability technique

This paper experimentally investigates the size-dependent effective Young's modulus E eff of aluminum (Al) clamped-clamped microbeams using the electrostatic pull-in instability technique. This study presents an experimental characterization of the so-called “length scale parameter” in couple stress theory and surface elasticity. E eff is retrieved from the measured pull-in voltage, of the clamped-clamped beams with different dimensions, via an electromechanically coupled equation. Measurement results show a strong size dependence of E eff for the Al beams in small sizes. The Young's modulus increases monotonously as the beams become thinner. The experimental observations are consistent with the published modeling results of the size effects, in which couple stress theory and surface elasticity theory are taken into consideration. The presented experimental method has substantial advantages such as precise adjustable magnitude of the non-contacting force and a lower cost over the other approaches used for characterization of micro-/nanoelectromechanical systems. This simple and reproducible method can be extended for characterization of various materials with different sizes and boundary conditions.