Interfacial properties and the response of the thickness-shear-mode acoustic wave sensor in liquids

The behavior of the piezoelectric acoustic wave sensor of the thickness-shear-mode type in various liquids has been characterized by the network analysis method. Models for this system based only on bulk liquid parameters fail to explain the behavior of the device with respect to series resonant frequency. Use of sensors with controlled surface free energy of the metal electrodes has been employed to demonstrate the importance of the liquid-solid interface in determining the response of the device. The contribution of the effects of surface roughness on the sensor response is discussed. Additionally, a previously-published four-layer model is successful in predicting the trends in values for the series resonant frequency for a set of mixed water-methanol solutions. © 1993 American Chemical Society.