The Response of Micro-scale Devices Subject to High-g Impact Stimuli

Recent advances in MEMS fabrication technology have resulted in a proliferation of microscale mechanical devices, some of which are applied in environments with severe levels of shock. The objective of this paper is to investigate the use of experimental and simulation methods in quantifying the behaviour of representative MEMS devices subject to high-g impact stimuli. Representative micro-cantilevers were analyzed under vibration and shock in order to determine the mechanical properties of single crystal silicon. The characteristic dimensions of the beams were of 100μm in height/width with beam lengths ranging from 5-7mm. Controlled vibration and shock tests were carried out on a modified Hopkinson pressure bar and a vibration table. The experimental approach allowed non-invasive in-situ monitoring of the micro-cantilevers upon impact through Laser Doppler Vibrometry (LDV) and high-speed imaging (HSI). An investigation of the shock response of representative micro-cantilever beams indicates that orientation plays a significant role in their sensitivity to shock due to the planarity of the fabrication technique. Finite element analysis in conjunction with in-situ HSI proved to be a viable non-invasive inverse technique to determine the loci and amplitude of tensile stress within generic micro-scale devices.