A semi-numerical model of a lateral field excited piezoelectric fluid sensor

The utilization of piezoelectric discs excited by lateral fields (LFE) for liquid phase sensing was first proposed by Vig in 1998. Since then, experimental investigations showed that LFE resonators show unique differences compared to common thickness field excited (TFE) resonators when used for liquid sensing. Due to the various modes of oscillation excited by LFE, the impedance spectrum cannot be properly calculated by one dimensional analysis, mostly sufficient for TFE. In our contribution, the interaction of piezoelectric disc and sample liquid, which is not fully manageable in an analytical way or too comprehensive for FEM, is modeled in a full-wave fashion by means of a semi-numerical method in the spectral domain (wavenumbers). The simulation results - shown for AT cut quartz and lithium niobate - enable a detailed analysis of the associated modes and their interaction with the liquid and qualitatively reproduce experimental data given in the literature.