Polyaniline-Coated Surface Acoustic Wave Sensor for Humidity Detection

In this paper, a polyaniline (PANI)-coated Surface Acoustic Wave (SAW) sensor was developed for humidity detection. Based on the coupling-of-modes (COM) simulation, 150 MHz two-port SAW resonators with low insertion loss and high Q factor were designed and fabricated on the ST-X quartz substrate with Al strips. Dual-resonator oscillator was built for gas sensing, and it was composed of a reference SAW resonator and a PANI-coated one. Large sensor response and good repeatability were observed in the sensor experiment. The effect of the PANI thickness on sensor response was also investigated.