TitleOptical whispering-gallery mode spectroscopy for the study of molecule adsorption and desorption
NameHuang, Lei (author), Guo, Zhixiong (chair), Rossmann, Tobias (internal member), Tse, Stephen D (internal member), Jiang, Wei (outside member), Rutgers University, Graduate School - New Brunswick,
SubjectMechanical and Aerospace Engineering,
DescriptionSensing applications utilizing whispering gallery mode (WGM) excited in circularly shaped microresonators were investigated. Complete theoretical analyses of were carried out. A WGM coupling system and its fabrication procedures were developed and characterized to produce high quality WGM resonances. The WGM spectral shift induced by the refractive index change in a nanostructured silica coating was experimentally investigated in response to environmental humidity changes. Following the experimental studies, label-free detection of biomolecules using an optical whispering-gallery mode sensor in a microelectrofluidic channel was simulated via the finite element method. The adsorption process of the analyte molecules on the microsensor head surface was monitored by the resonance frequency shifts. Frequency shift caused by temperature variation due to Joule was analyzed to be not comparable to that induced by the analyte deposition. The induced shifts were found to behave in a manner similar to Langmuir-like adsorption kinetics. A correlation of the frequency shift, the analyte concentration in the solution, and the applied voltage gradient was obtained, in which an excellent linear relationship between the frequency shift and the analyte concentration was revealed and an exponent relationship between the applied voltage gradient and the resonance frequency shift was illustrated, indicating the applied voltage enhances the shift in an extremely dilute solution. The applied voltage gradient was found to affect the adsorption capability; and thus, the sensor sensitivity. Simulated detection of extremely low protein concentration to the pico Molar level was carried out. The optical WGM micro resonator with integrated functions of the optical sensing and nanofiltration embedded in a microelectrofluidic system was proposed and studied afterwards. The filtration process and anlyte concentration were traced by measuring the WGM resonance frequency shift. The applied voltage gradient was found to influence the filtration capability through its effect on adsorption and desorption processes. The higher order of WGM was found to be able to provide a higher sensitivity as comparing with lower ones.
NoteIncludes bibliographical references
Noteby Lei Huang
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.