Date of Award
Summer 2005
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Electrical and Computer Engineering
First Advisor
Schneider, Susan
Second Advisor
Josse, Fabien
Third Advisor
Hossenlopp, Jeanne
Abstract
The use of polymer-coated acoustic wave devices for the detection and identification of analytes in aqueous environments is commonly used in the implementation of chemical and biochemical sensors. The design and analysis of these types of sensors require an appropriate characterization of the chemically sensitive coating. This characterization relies on information about the viscoelastic properties of the polymer films and subsequent changes upon exposure to environmental factors, such as liquid contact. In this thesis, the use of the thickness-shear mode (TSM) quartz resonator is proposed for the rapid characterization of the polymer, poly(isobutylene) (PIB), under various conditions including; exposure to air, DI water and varying concentrations of analytes. The electromechanical behavior of the TSM resonator can be modeled as an equivalent circuit. This equivalent circuit model can be described with a few lumped elements (resistance, capacitance and inductance), and simulates the electrical characteristics of the TSM resonator over a range of frequencies near resonance. This model can explicitly relate the lumped elements in the circuit to physical properties of the TSM, as well as the surface loading (liquid load and/or viscoelastic film). The electrical responses of the PIB-coated device were examined at the device's fundamental frequency of 9-MHz. The thickness shear mode (TSM) resonators were coated with different thickness values of the PIB polymer, and a network analyzer was used to operate the device and measure the admittance responses near resonance as a function of thickness. The PIB coatings were exposed to DI water and then varying concentrations of aqueous solutions of ethyl benzene and toluene, in each case the admittance spectra were measured and analyzed. A general model that incorporates a diverse set of single-component loads including the viscoelastic media and fluids resulting in a non-linear relationship between the total surface mechanical impedance and the changes in the characteristic mechanical impedance of the film and the fluid was used to extract the viscoelastic property, the shear modulus G (= G' + jG"), where G' is the storage modulus and G" is the loss modulus, of the polymer film. The analysis and extraction of the viscoelastic properties, G' and G", of the Pill films in contact with air showed good agreement with published values under comparable conditions. The extraction of the viscoelastic properties in DI water showed trends which are in agreement with the nature of polymer; in terms of it's interaction and stability in water. The extracted viscoelastic changes of the Pm polymer upon analyte sorption in the liquid phase showed that thicker film experience greater variations in G' and G".
Recommended Citation
Amu, Ohiorenuan Jude, "Characterization of Poly(isobutylene) (PIB) in a Aqueous Environment Using Thickness-Shear Mode (TSM) Resonators" (2005). Master's Theses (1922-2009) Access restricted to Marquette Campus. 3924.
https://epublications.marquette.edu/theses/3924