Two-dimensional FEM analysis of pressure wave generation mechanisms in TSM liquid sensors

Due to benefits like high sensitivity, small size, and cost-effective fabrication, acoustic wave sensors have gained considerable importance. For sensing tasks in liquid media, thickness-shear mode (TSM) resonators are commonly utilized devices, as they ideally do not lead to an unwanted excitation of pressure waves in the liquid. However, due to the finite lateral extension of the resonator, spurious pressure waves are radiated into the adjacent liquid. These pressure waves are largely undamped, which can lead to disturbing interference effects if they are reflected by objects in the vicinity of the sensor. To gain insight into the associated phenomena, we recently performed a 3D finite element (FE) analysis where different excitation mechanisms were identified. However, due to the numerical complexity, these phenomena cannot be accurately studied in a 3D FE-analysis. In this paper we present a more extensive 2D model, which allows us to investigate these effects in depth.