“…A SAW device with high sensitivity, fast response and low cost can be used in kinds of applications [1,2] such as indoor air measurement, food product quality control, environmental monitoring [3,4], military applications, and national security. Comparing with other microsensors such as potentiometric charge sensitive devices, thermally based detectors, and chemiresistors [5,6], an electronic nose device has higher sensitivity, smaller size and cheaper cost. The advantage of high sensitivity results from the fact that surface acoustic waves are mostly confined to the piezoelectric substrate surface within one or two wavelengths and thus are very sensitive to changes of sensitive film properties such as the surface electrical conductivity, elastic moduli, mass, and permittivity when exposed to target gases.…”