Gas sensor based on nonlinear coupled AlN-piezoelectric micromachined resonators

This paper reports a novel Aluminium-Nitride (AlN)-based piezoelectric micromachined gas sensor relying on thermal energy dissipation (heating or cooling) of an electrically heated weakly coupled resonator. The coupled MEMS resonator, consisting of a bridge and cantilever resonators mechanically coupled, was driven by applying AC voltage to an AlN-piezoelectric layer coated on the clamped-clamped beam. The frequency and the velocity spectra are studied with a laser Doppler vibrometer. The buckling behaviour of the devices under high electrothermal voltage was analyzed. Moreover, two modes veering phenomena were observed and discussed. Sensing performance for two operation points before and after the buckling point was explored experimentally for increasing concentrations of Helium. The results yield different directions of frequency shift with 3.123%/kHz and 1.089%/kHz slope respectively, showing the great potential for high-performance gas sensing.