Modeling a piezoelectric TSM sensor to study kinetics of multi-layer biosensing structure

Most of the biological processes are surface mediated; but limited techniques are available to study interfacial biological processes. These techniques exhibit significant limitation due to their low sensitivity and selectivity, and poor temporal resolution. We are studying a novel measurement technique which utilizes piezoelectric thickness shear mode (TSM) sensor for the study of interfacial biological processes in real time. A typical real-life biological system is a multi-layer system comprising of several biological surfaces or interfaces. This multi-layer sensing structure loaded on piezoelectric TSM sensor has been simulated based on Mason´s model, which represents each layer as T-network of acoustic and electrical impedances. Each layer is described by its mechanical properties (stiffness, viscosity, density) and geometrical properties (thickness). These properties can be varied for a variety of material parameters which represent broad range of biologically relevant operation conditions. Our model predicts the changes in the total impedance of the sensor system, which is related to the resonance frequency and amplitude of the sensor. In turn, these changes can be related to the ongoing biological processes. The study shows three different processes simulating interfacial phenomena and gelation (solidification) of materials