Fabrication of high-resolution strain sensors based on wafer-level vacuum packaged MEMS resonators

Abstract

The paper reports on the fabrication and characterization of high-resolution strain sensors for structural materials based on Silicon On Insulator flexural resonators manufactured by polysilicon Low-Pressure Chemical Vapour Deposition vacuum packaging. The sensors present sensitivity of 164Hz/με and strain resolution limit of 150pε on steel for a measurement time of 315ms, in both tensile and compressive strain regimes. The readout of the sensor is implemented with a transimpedance oscillator circuit implemented on Printed Circuit Board, in which a microcontroller-based reciprocal frequency counter is integrated. The performance of the sensors on steel are investigated for measurement bandwidths from 1.5 to 500Hz and a comparison with conventional metal strain gauges is proposed.