Development of a preconcentration unit for a SAW sensor micro array and its use for indoor air quality monitoring

A new surface acoustic wave (SAW) sensor system for continuous monitoring of air quality was developed. The system employs a miniaturized array of eight polymer coated SAW sensors, a preconcentration unit (‘trap’), and methods of pattern recognition. Care was taken to minimize both the response times of the sensors and the gas volume of the sensor array. Thus, a small trap with low heat capacity can be used, resulting in low power consumption and rapid thermal desorption. The capabilities of the system are demonstrated by successful discrimination of closely related aromatic compounds (BTXE) in the low- and sub-ppm ranges. Design considerations are made with particular emphasis on the necessities arising from the interplay between sensors, coatings, trap, gas fluidics, and pattern recognition software.