Acoustic plate mode devices as liquid phase sensors

Acoustic plate mode devices (APMs) which show considerable promise as sensors of liquid properties and solution species, and as probes of the solid-liquid interface are described. Their sensitivity to a variety of parameters including viscosity, dielectric coefficient, ionic conductivity, and changes in surface mass and mechanical properties allow a variety of sensors to be constructed. At the same time, the relative magnitude of each of these effects must be considered at all times to properly interpret experimental results. The experimentally determined mass sensitivity of the 158-MHz APM in 0.19 mm thick ST-quartz, 44 cm/sup 2//g, is about one-third of the 97 MHz SAW mass sensitivity, but nevertheless allows accurate measurement of fractional monolayer mass changes at the solid/solution interface.<>