Thin-film-bulk-acoustic-resonator gas sensor for the detection of organophosphate vapor detection

A novel design of an organophosphate vapor sensor based on a thin film bulk acoustic resonator (TFBAR) is presented. The TFBAR device is consisted of an AlN piezoelectric stack and a Mo/AlN Bragg reflector. Poly (vinylidene fluoride) (PVDF) is coated on the surface of the piezoelectric stack as the special sensitive layer. The concentration of the target gas can be analyzed by measuring the resonant frequency. Adsorption of organophosphate compounds onto the PVDF can increase its mass, and the frequency proportionally goes down. The results show that the TFBAR sensor can yield a rapid, sensitive, reversible and reproducible response to dimethyl methyl phosphonate (a stimulant of sarin) vapor. The gas sensitivity of the proposed sensor is 220 kHz ppm^-1 in the the vapor concentration range of 2-30 ppm. This study proves that using the chemical functionalized thin film bulk acoustic resonator to detect the trace hazardous gas is feasible.