DEVELOPMENT OF AN ANALYTICAL MICROSYSTEM FOR ORGANIC GAS-DETECTION BASED ON SURFACE-ACOUSTIC-WAVE RESONATORS

Modified Surface Acoustic Wave (SAW) devices can be used as highly sen sitive detectors for gases: coated with a selective sorptive layer, th ey serve as a frequency determining element of an oscillator circuit. To perform a quantitative analysis of organic gas mixtures with polyme r coatings as sensitive membranes, it is necessary to use an array of several SAW sensors with sensitivities towards various gaseous compone nts and a subsequent pattern recognition of the sensor responses. An a utomatic working, self purging and compact analytical microsystem has been developed for organic gas detection. As the central component it contains an array of nine commercially available SAW resonators workin g at frequency of 433.92 MHz. Eight sensor oscillators, one common ref erence oscillator for temperature compensation and circuits for freque ncy mixing are mounted within a compact radial housing (diameter 108 m m). A selection of polymers has been made to detect a broad variety of gaseous organic analytes. Of particular interest have been hydrocarbo ns, halogenated hydrocarbons and aromatic compounds. Initial experimen ts with these analytes have been carried out to proof the selection an d to optimize the combination of polymer coatings. With the compact se nsor configuration a very fast response time in the range of seconds i s obtained for qualitative determination of the analytes.