Doctor of Philosophy

dissertationThis dissertation describes the integration of a microfluidic flow cell array (MFCA) with surface plasmon resonance microscopy (SPRM) and the application of MFCASPRM system for microarray analysis of biomolecule interactions. The design and construction of a SPR microscope with a sensing area that is compatible with the fluidics footprint of the MFCA is described first. Antibody-antibody interactions are used as the model system to demonstrate the capability of the integrated MFCA-SPRM for in situ microarray fabrication and analysis. Impacts of physicochemical parameters, such as reactant concentrations, reaction constants and the flow rate, on the performance of the MFCA-SPRM are investigated by experiments and modeling. Optimized experimental conditions will support the future application of the MFCA-SPRM. Statistical analysis of microarray data (24 micro spots) shows that the spot-to-spot coefficient of variation is within 15%. Major sources of signal variance are from the deviation of light incident angle, heterogeneous sensing surface and the mass transport. Next, a proof-of-principle experiment demonstrates the potential of the MFCA-SPRM system for immunogenicity assays of Daclizumab to analyze anti-drug antibodies (ADA) from serum samples. Daclizumab is a monoclonal antibody drug for treatment of multiple sclerosis patients. Biotinylated-Daclizumab immobilized on a streptavidin monolayer is used to assess the presence of ADA in serum samples of three patients with multiple sclerosis. The result shows that the sample from a patient without the treatment of Daclizumab generates the highest SPR signal. In the future, more samples are required to generate statistically significant data to evaluate the immunogenicity of Daclizumab. Matrix-assisted laser desorption/ionization mass spectrometer (MALDI MS) is an ideal tool to be combined with SPR for protein analysis. An antibody microarray created by MFCA and coupled to MS is utilized to demonstrate the potential of microarray analysis with SPR-MS. Finally, we apply MFCA-SPRM system for characterization of in situ immobilized vesicles on solid surfaces. Hydrophilicity of surface, vesicle size and composition are investigated as factors that affect the structure of vesicles adsorbed on surfaces. A model for the calculation of the surface area of the bilayer is proposed to correlate the SPR response with vesicle structures at the surface

Effects of Chirality and Coherence on Light Scattering

In the first part of this dissertation, we study the light scattering properties of particles with chiral structures. Special attention is paid to the dinoflagellates, known for their circular polarization effects and as a causative agent of the red tide. Based on experimental observations and previous works, we build a helical plywood liquid crystal model for the nucleus of dinoflagellates, and apply the Discrete Dipole Approximation (DDA) method to investigate the light scattering properties of dinoflagellates. The backscattering signals display strong sensitivity to the wavelength of the incident beam, and they are most prominent when the wavelength matches the pitch of the chromatic helix. Our results indicates a promising means to monitor and detect the specific species of dinoflagellates. In the second part of the dissertation, we investigate the the problem of light scattering when the incident light has finite coherence length. The conventional Lorenz-Mie theory and DDA method are generalized to include a partially spatially coherent source. The formalism is applied to atmospheric particles such as water droplets and hexagonal ice crystals. Given that the solar source is partially coherent, our results have practical implications in remote sensing. Using the same technique, we also study the effects of incoherence on particle characterization using digital holographic microscopy. We show that holography is rather robust against incoherence and demonstrate the possibility of retrieving the coherence length of the illumination

Device-free Localization using Received Signal Strength Measurements in Radio Frequency Network

Device-free localization (DFL) based on the received signal strength (RSS) measurements of radio frequency (RF)links is the method using RSS variation due to the presence of the target to localize the target without attaching any device. The majority of DFL methods utilize the fact the link will experience great attenuation when obstructed. Thus that localization accuracy depends on the model which describes the relationship between RSS loss caused by obstruction and the position of the target. The existing models is too rough to explain some phenomenon observed in the experiment measurements. In this paper, we propose a new model based on diffraction theory in which the target is modeled as a cylinder instead of a point mass. The proposed model can will greatly fits the experiment measurements and well explain the cases like link crossing and walking along the link line. Because the measurement model is nonlinear, particle filtering tracing is used to recursively give the approximate Bayesian estimation of the position. The posterior Cramer-Rao lower bound (PCRLB) of proposed tracking method is also derived. The results of field experiments with 8 radio sensors and a monitored area of 3.5m 3.5m show that the tracking error of proposed model is improved by at least 36 percent in the single target case and 25 percent in the two targets case compared to other models.Comment: This paper has been withdrawn by the author due to some mistake