A liquid sensor based on a shear horizontal saw device

Publisher Website
Google Scholar
Abstract
The surface acoustic wave (SAW) changes its propagation characteristic if the region above the propagation surface is altered. This phenomenon can be used for realization of an SAW sensor. The Rayleigh mode known as a general SAW can be used as a gas phase sensor. If, however, the propagation surface is loaded with liquid, a longitudinal wave is radiated into the liquid and the Rayleigh wave decays. Hence, this wave cannot be used for a liquid sensor.To realize a liquid sensor, the SH mode must be used in which the particle displacement is normal to the propagation direction and parallel to the propagation surface. It has been reported that the SAWs propagating on piezoelectric crystals such as 36° rotated Y‐cut X propagation LiTaO3and X‐cut 150° propagation LiTaO3are SH‐mode SAWs (SH‐SAW).In this paper, it is found theoretically and experimentally that the shear horizontal‐ (SH‐) SAW devices using these piezoelectric crystal cannot only detect the mechanical effects such as the viscosity of the liquid and the mass loading in the liquid but also the electrical effects such as the permittivity and conductivity of the liquid. By way of comparison with other liquid sensors using high‐frequency ultrasonic devices, the characteristics of the SH‐SAW sensors are clarified.

This publication has 10 references indexed in Scilit: