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theses

Optical scatter imaging (OSI), which combines light scattering spectroscopy with microscopic imaging, offers an alternative and efficient way for non-invasive and dynamic study of particle and cell morphology with high signal throughput in real time. A variable diameter iris as a Fourier spatial filter allows the OSI microscope to generate images that encode the intensity ratio of wide-to-narrow angle scatter (OSIR, optical scatter imaging ratio) at each pixel. One part of this study focused on designing and constructing a miniaturized OSI microscope setup adopting reflectance mode with Fourier filtering based on original OSI setup. Recently, the ZnO nanostructure-modified quartz crystal microbalance (ZnOnano-QCM) biosensor has been receiving increasing attention for its dynamic and noninvasive cellular monitoring properties. The goal in this part of the study is to design an optical imaging modality that can be combined with the ZnOnano-QCM biosensor. The second part of the study is focused on evaluating the performance of this miniaturized OSI microscope setup. Our results demonstrate a compact OSI microscopy system which was build using aspheric lenses, a LED light source, and a low-budget CCD camera. The results show that the microscope aperture of our OSI setup had an NA of 0.55 corresponding to a spatial resolution of 0.6µm, the magnification was 8X, and the field of view was 596 x 446µm. Theoretical simulations of the forward scattered and the backscattered OSIR show that the backscatter OSIR fluctuates more as a function of particle size compared with the forward scatter OSIR which varies monotonically as a function of sphere diameter. When samples were mounted on non-reflective matte black metal slides, the backscattered OSIR of onion cells and microspheres were measured and the experimental data demonstrate that the measured OSIR agrees well with theoretical predictions for microspheres with diameter between 0.7µm and 1.8µm. Onion cell dark-field images on the matte black slides were of good quality and compared well with bright field images collected on a standard phase microscope. However, when samples were mounted on glass or in an aqueous medium with a spatial filter, the acquisition of clear dark-field images of live endothelial cells failed since the spatial filter could not block the specular reflection perfectly. As such, the OSI microscope that was developed provides a proof-of-principle for conducting the OSIR measurement in reflectance mode. However, further improvements are needed to eliminate the background due to specular reflection in samples.

ETD_8494

M.S.

Includes bibliographical references

by Jiawei He

doi:10.7282/T3SJ1PR8

ETD graduate

The author owns the copyright to this work.