Numerical Analyses of a SAW Gas Sensor in a Non-Steady State

This document describes numerical analyses performed on a SAW gas sensor in a non-steady state. Our work involved predicting SAW velocity changes in relation to the surface electrical conductivity of the sensing layer. We found that the conductivity of the rough sensing layer (above a piezoelectric waveguide or quartz) is determined by the diffused gas molecule concentration profile inside it. Specifically, we present numerical results for the DMMP gas concentration profile (CAS Number 756-79-6) within an (RR)-P3HT layer during the non-steady state recovery step. The core of these investigations was to understand thin film interaction with target gases in a SAW sensor configuration, using the diffusion equation for polymers. The outcomes of these numerical analyses provide valuable insights for selecting sensor design conditions, including the sensor layer's morphology, thickness, operating temperature, and type. The numerical results, generated using Python code, are then elaborated upon and examined.