Piezoelectric Layered Structure with Conductive Polymer Composites as a Waveguide Layer: Swelling Monitoring Based on the Propagation of Love-Type Wave

Conductive polymer composites (CPCs), characterized by adjustable material parameters and specific responsiveness to external stimuli, exhibit potential utility as waveguide layers on surface acoustic wave (SAW) devices for monitoring applications. In this study, we examine the effect of swelling on the propagation of Love-type waves by subjecting a layered structure composed of a 36° Y-X lithium tantalate (LT) substrate and CPC waveguide layer. Love-type waves are first identified, and the propagation characteristics are analyzed by simulation and experimental comparison on polydimethylsiloxane (PDMS)-based CPC waveguide layers, which are filled with different acetylene carbon black (ACB) mass fractions. The influence of Love-type wave propagation after being subjected to a chemical medium is further explored. The results show that the characteristic frequency shifts of the SAW device are related to the observed swelling response of the ACB/PDMS CPCs. The experimental results are in agreement with simulations, and the frequency shifts with waveguide layer thickness variation are theoretically verified. This study illustrates the use of CPCs as a waveguide layer to modulate the propagation of Love-type waves and explores their application prospects for swelling monitoring.