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

•Wafer level vacuum packaged flexural resonators are fabricated.•The MEMS are employed as strain sensor fort structural material by exploiting their mechanical resonance frequency dependence on strain.•High strain resolution of 150pε and strain sensitivity around 164Hz/με on steel is reached in tensile and compressive regime for a measurement time of 315ms.•The readout of strain sensor is realized on Printed Circuit Board in which a microcontroller-based reciprocal frequency counter is integrated. 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.