Surface Acoustic Wave Sensor for Protein Characterization: Fabrication, Modeling and Simulation

This thesis investigates the usage of surface acoustic wave (SAW) devices as sensors in the determination of viscosity of Newtonian fluids such as Bovine Serum Albumin (BSA). Specifically, conductance and susceptance data of the SAW device in the presence of Bovine Serum Albumin and other liquids, comprising of proteins in small quantities (~35 nL). A two-port SAW device (320 MHz) was fabricated and tested with different concentrations of a water-miscible BSA in deionized water (DI water) and glycerol. The study examines several designs and type of substrates. There is a strong correlation of the measured sensor data to the corresponding computer simulations. A Finite Element Model (FEM) of the Two-Port Surface Acoustic Device is used to simulate the Sensor characteristics. COMSOL Multiphysics Modeling and simulation of surface acoustic wave devices are also utilized for protein characterization. The models predict how the presence of fluid in the groove lowers the resonance frequency. The SAW Sensor simulation detects changes in the viscosity of a protein using thermoviscous acoustic - piezoelectric interactions. The model accurately predicts the behavior of the SAW and fluid interactions. Rigorous analysis of viscosity and resultant variations in conductance, susceptance, and admittance, as a function of Protein concentration and morphology, establish SAW sensors as significant characterization devices. New drug discovery and development is costly; of all compounds investigated for use in humans, only small fractions are approved for treatments. The pharmaceutical industry has started switching from molecular drugs to protein-based drugs due to high specificity, enhanced efficacy, affinity, solubility, and low toxicity. Novel proteins in elevated concentrations are very expensive to produce. On the other hand, their solution properties, especially the viscosity is very critical to the stability, processing, manufacturing, and delivery of such drugs.