A surface acoustic wave/polymer gas sensor for use in a hybrid oscillator circuit

Abstract

Polymer coated surface acoustic wave (SAW) microsensors were used to detect low concentrations of hydrocarbon based gases. SAW sensors are known to be highly sensitive and can be incorporated in oscillator circuits for commercial applications. In this work, HFDA photosensitive and non-photosensitive polyimides were tested for sensitivity, repeatability, and selectivity using both SAW phase and frequency methods. Both polyimides were highly sensitive to water and methyl-ethyl-ketone (MEK) and had some sensitivity to n-octane, iso-octane, and n-heptane. The photosensitive HFDA polyimide showed significandy larger responses to gas sorption than the non-photosensitive polyimide and also had an increase in response of up to four times as it was aged.