A chemical surface acoustic wave(SAW) sensor array for sensing different concentration of NH3

Surface acoustic wave (SAW) sensor is generally known as high-resolution mass-sensitive transducers. We developed a novel SAW sensing array based on 2 × 2 non-continuously working oscillators equipped with differently coated SAW sensors, respectively, which is used to analyze organic compound gases. The sensing array consisting of four two-port SAW resonator sensors with a fundamental frequency at 99.8 MHz was fabricated on LiNbO₃ substrate. Four different polymers were coated on the surface of sensing regions. The gas sensing array was put into 10L reaction chamber with temperature and humidity controllable environment. The frequency outputs from each sensor were used to compare with the frequency from a reference device for eliminating the environmental effects. The results suggest that frequency shift of the designed gas sensor array changes with different concentration of the target gas(NH₃).