Guided waves propagating in a piezoelectric plate immersed in a conductive fluid

In this paper, a theoretical and experimental study on a leaky Lamb wave (LLW) propagating in a piezoelectric plate loaded by a dielectric/conductive fluid is presented. The analysis is based on a partial wave analysis for the piezoelectric plate, taking into account the mass and dielectric/conductive loading of the fluid. Based on theory, dispersion curves, presented in the form of reflection coefficient minima, can be obtained for an X-cut LiNbO₃ plate immersed in a fluid with various levels of conductivity. Commonly used as a measure in chemical micro-sensors, the frequency shift of LLW modes induced by the change of fluid conductivity was also calculated to see if it matched theoretical predictions. Our results show that our theoretical calculations verify our experimental study, which applied bulk wave ultrasound transducers to measure the frequency shift for various levels of fluid conductivity.