Polymer-coated surface acoustic wave sensor array for low concentration NH3 detection

Surface acoustic wave sensors are famous for its low cost, high resolution, and quick response time. In this paper, the SAW gas sensor for detecting low concentration of NH₃ was presented. The gas sensor array is composed of 2×2 non-continuously working oscillators equipped with one reference SAW sensor and three SAW sensors coated with different polymers. To improve the selectivity and sensitivity, ten kinds of polymers with special functional group were coated on the sensing area as the sensing film. The gas recognition database was established by collecting and normalizing the results of interplay between polymers and target gas. The miniaturized SAW chip was developed for low cost and portability, more capacities of polymer-coated SAW sensors mounted on a limited region of sensor array chip. The PNVP-coated miniaturized SAW sensor has been successfully developed to detecting low concentration ammonia of 16 ppm. Compared with the original SAW sensor, the miniaturized SAW sensor coated with PNVP film shows larger frequency shift but similar performance for low concentration of NH₃ detection after normalizing the results of interaction between polymer and ammonia.