Gas sensor application of piezoelectric cantilever nanobalance; Electrical signal read-out

We have fabricated piezoelectric microcantilever transducer for a miniaturized gas sensor, to detect environmental gas molecules, i.e., volatile organic compound (VOC). The microcantilever consist of Pb(Zr, Ti)O-3 (PZT) capacitors and SiNx layer as an actuating and a supporting layer respectively. The fundamental resonant frequency of microcantilever was in the range of 17 similar to 29 kHz. To measure the gas sensitivity, the microcantilever surface was coated with polymethylmetacrylate (PMMA), which is known to have sensibility for primary alcohols. The resonant frequency shift of the microcantilever was measured by complex impedance analysis, which only uses electrical signal output from the microcantilever. As the vapor concentration of the alcohol (ethanol or methanol) increased, the resonant frequency of microcantilever was linearly shifted toward the lower frequency range. The gas sensitivity of microcantilever was 0.03 Hz/ppm for methanol vapor.