Surface acoustic wave (SAW) devices find uses in a plethora of applications including
but not limited to chemical, biological sensing, and microfluidic actuation. The primary aim of
this dissertation is to develop a SAW biosensor, capable of simultaneous detection of target
biomarkers in fluid media at concentrations of picogram/ml to nanogram/ml levels and removal
of non-specific proteins from sensor surface using the process of acoustic streaming, for potential
chemical sensing, medical, and clinical diagnostic applications. The focus is on the development
of three dimensional finite element structural and fluid-structure interaction models to study wave
propagation and acoustic actuation of fluids in a SAW biosensor. This work represents a
significant improvement in understanding fluid flow over SAW devices, over the currently
available continuum model of Nyborg. The developed methodology includes use of a novel
substrate, namely, Langasite coupled with various combinations of novel multidirectional
interdigital transducer (IDT) configurations such as orthogonal, focused IDTs as well as sensor
surface modifications, such as micro-cavities. The current approach exploits the capability of the
anisotropic piezoelectric crystal to launch waves of different characteristics in different
directions, which can be put to the multiple uses including but not limited to sensing via
shear
horizontal waves and biofouling elimination via
Rayleigh wave induced acoustic streaming.
Orthogonal IDTs gives rise to constructive interference, thereby enhancing the magnitudes of
device displacements and fluid velocities. The net effect is an increase in device sensitivity and
acoustic streaming intensity. The use of micro-cavities in the delay path provides a synergistic
effect, thereby further enhancing the device sensitivity and streaming intensity. Focused IDTs are
found to enhance the device displacements and fluid velocities, while focusing the device
displacements and fluid motion at the device focal point, thereby enhancing the SAW device
biosensing performance. The work presented in this dissertation has widespread and immediate
use for enhancing sensor sensitivity and analyte discrimination capabilities as well as biofouling
removal in medical diagnostic applications of SAW sensors. This work also has a broad relevance
to the sensing of multiple biomarkers in medical applications as well as other technologies
utilizing these devices such as microfluidic actuation.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-4901 |
| Date | 01 October 2009 |
| Creators | Singh, Reetu |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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