A system for the dynamic characterization of microstructures

This article describes a fully automated measurement system designed to evaluate the dynamic characteristics of micromechanical structures (millimeter dimensions), To validate the system, vibration measurements have been carried on two structures-a micromachined silicon cantilever and bridge-and the results are presented, Out-of-plane measurements show that for the cantilever, both the mode shapes and resonant frequencies agree with beam theory predictions, However, for the bridge structure, tension due to boron doping causes a change from beam-like behavior and a more complex model is required, Mode-shapes natural frequencies and modal damping are determined from data obtained by vibrating the structures using a piezoelectric mounting system and deriving the transfer function between the piezodrive voltage and beam vibrational velocity.