Algorithms for the real-time analysis of SAW chemical sensor array data

SAW chemical sensors are surface acoustic wave devices that have been coated with a thin layer of chemoselective material, e.g. a functionalized polymer. The SAW chemical sensor is sensitive to mass and physical changes in the properties of the coating. The chemoselective polymer is tailored for gas(es) of interest and acts as a sponge to concentrate gas at the surface of the SAW device. During operation, a wave is directed across the surface of the SAW device, and when the polymer coating sorbs gaseous molecules, the velocity of the surface acoustic wave is perturbed. The sorption of a gas is readily detected by monitoring the oscillating frequency of the device. Although no single SAW device is selective to a single compound, arrays of SAW sensors can be used in conjunction with pattern recognition techniques to detect and identify a wide variety of gases. The prototype SAW sensor system described in this paper is called the SAWRHINO. The SAWRHRINO includes two temperature-controlled 3-SAW sensor arrays with an automated dual gas sampling system.