MEMS resonant sensors for detection of gasoline vapor

This work demonstrates detection of organic vapors in the air using micromechanical resonators Fully silicon thermally actuated resonators with piezoresistive readout have been utilized to detect presence of gasoline vapor in air. The resonators have been fabricated using a single mask process on SOI substrates and have resonant frequencies in the sub-MHz to a few MHz range. Using a thin arbitrary polymer coating as the absorbent layer, frequency shifts in the order of 200 ppm were measured for the resonators upon exposure to gasoline vapor. This is equivalent to ~10 nm absorbed gasoline thickness. Measured response time constants are around 4 minutes. Faster and more sensitive responses are expected to be achievable using more appropriate absorbent layers and optimized resonator designs.