Gas sensor array based on surface acoustic wave devices for vapors detection and analysis

We have developed a new electronic nose based on a gas sensor array to detect organic vapors. The gas sensor array is based on 2×2 non-continuously working oscillators equipped with differently polymer-coated surface acoustic wave (SAW) sensors. The SAW detection system which is employed to detect various organic molecules in a static system was prepared using 99.8 MHz two-port SAW resonators and a computer for signal acquisition and data process. This gas sensor array system consists of SAW sensors, polymers with different polarity and function groups, and signal readout electronics. We select the appropriate coating materials on to the SAW crystal (LiNbO₃) for organic vapors, e.g. poly(4-vinylphenol), poly(vinyl acetate), poly-ethylene-glycol, poly-styrene-co-maleic, anhydride, polystyrene and poly-sulfone. In this study, we focus on the detection of vapors like methanol, ethanol, isopropyl alcohol (IPA), acetone, amine, and trimethylamine (TMA). Finally, we get the good result of tree-view from the two-way hierarchical clustering analysis after comparing the correlation between the 6 coating materials and 6 organic vapors. These organic vapors could be clearly distinguished by the tree-view. Furthermore, the SAW detection system can distinguish unknown gas or mixed gas by the database of pattern recognition in the future.