DESIGN AND ANALYSIS OF A RAYLEIGH SAW RESONATOR FOR GAS DETECTING APPLICATIONS

Polymer coated gas-phase sensors using the classical Rayleigh-type surface acoustic wave (RSAW) mode showed higher sensitivity and larger dynamic range compared to bulk acoustic wave (BAW) sensors, being widely used in a variety of sensor systems for chemical and biological gas detection. Using Comsol Multiphysics software, we investigated a 2D finite element model of a Surface Acoustic Wave (SAW) gas sensor, which consists of an interdigitated transducer (IDT) etched onto a piezoelectric LiNbO3 substrate and covered with a thin Poly Isobutylene (PIB) film. We selected for this study a sensor with two IDT structure types: bi-directional and single phase unidirectional transducer and we computed the deformed shape plot of the resonance and anti-resonance SAW mode. The variation of electrical potential and total displacement as a function of structure depth (y coordinate) was also obtained. The sensor's sensitivity was evaluated by exposing the PIB film to various CH2Cl2 (Dichloromethane) concentrations.