ABSTRACT
The feasibility of applying surface acoustic wave (SAW) piezoelectric crystal technology to the measurement of subnanogram levels of particles and parts-per-million levels of surfur dioxide has been demonstrated. Mass sensitivity comparisons of a 158-MHz SAW piezoelectric microbalance and a conventional 10-MHz quartz crystal microbalance (QCM) showed that the SAW crystal was 266 times more sensitive. The application of the SAW device in mass-measuring instruments has been principally in the area of chemical sensing, in which a reactive coating applied to the surface of a SAW device responds specifically to a given gas through a mass change which, in turn, results in a frequency change. The SAW device used in these investigations was purchased from Microsensor Systems, Inc. (Fairfax, VA). The mass sensitivity comparison was made between the SAW crystal and a conventional 10-MHz QCM instrument in a side-by-side comparison.
