Modelling of the mass sensitivity of the Love wave device in thepresence of a viscous liquid

Abstract

This paper describes a new theoretical model for the analysis of themass sensitivity of the Love wave device. We use this model along withcalculations from perturbation theory to calculate sensitivity. The model isbased on Love wave propagation in an isotropic, non-piezoelectric quartzsubstrate over-layered by a silica waveguiding layer and immersed in aviscous liquid. The analysis considers power flow in the three-layered system,comprising the quartz substrate, the silica over-layer and the viscous liquid.The model fully accounts for the first time for the power that flows throughthe liquid phase and assesses its effect on mass sensitivity. Mass sensitivityvalues were obtained by determining the displacement field throughout theviscous liquid and the Love waveguide device. The resulting velocity field wasused to generate a number of trial functions that had solutions assumingstress and strain continuity at the boundaries, and the complex dispersionrelation was evaluated numerically. The resulting wavevector k and propagationconstant β values were used to calculate the power in both the Love wavedevice and the liquid layer and the velocity amplitude at the surface. Themodel predicts that the mass sensitivity of the Love wave device will increasein the presence of a viscous solution due to power flow into the liquid.