Development of microfluidic devices for biological analyses and energy applications.

摘要

Microfluidics deals with the behavior and manipulation of fluids within geometrically constrained structures with dimensions of typically sub-micrometer scale. Such a small microfluidic system can be easily customized by applying micro-/nanofabrication methods, and its ability to function with small inputs of sample and energy may lead to the development of fundamentally new analysis platforms with significantly superior performance compared to traditional ones. The main goal of this dissertation work was to understand some unique microfluidic features and apply the acquired knowledge to developing novel devices that improve our ability to perform biological analyses and designing more efficient portable electrical power sources. More specifically, this dissertation research has been focused in three major areas which involve designing microfluidic pumps, developing chip-based enzyme-linked immunosorbent assays (ELISAs) and exploiting nanofluidic transport phenomenon to generate electrical energy. The use of external pumps for implementing pressure-driven separation on microfluidic systems often leads to poor performance due to limited dynamic control over the transport of fluid and analyte samples. To address this issue, we fabricated a micro-pump inside of the device and demonstrated chromatographic separations under pressure-driven conditions using the integrated micro-pump. The application of microfluidic approaches to enhancing the sensitivity of enzyme-linked immunosorbent assays (ELISA) is another research area that we have investigated. ELISA is the standard laboratory technique employed in bio-medical fields for the identification and quantitation of particular antigens or antibodies. By utilizing a microfluidic platform, we were able to significantly improve its performance through pre-concentration of analyte molecules in a nanoliter-sized detection region. Reduction in sample volume requirement for this assay was also accomplished in a different project by assaying multiple target molecules in a single channel using the same enzyme label/substrate. In addition, while fluorescence measurements are most commonly used for quantitating microfluidic assays, we developed a new device that allowed absorbance measurement in an ELISA process using a commercial plate reader. The small optical path length for these measurements was increased by fabricating mirror layers on the device that reflected the incident light multiple times inside the channel. As the last microfluidic ELISA application, we explored the possibility of employing a commercial desktop scanner for quantitating the ELISA signal. Our findings may lead to realize portable and more affordable assay platforms. The final microfluidic research area that we have studied is the generation of electrical power through the use of fluid flow in a micro-/nanoscale channel. While the basic concept behind such a device has been previously demonstrated, we have looked at the possibility of realizing higher energy efficiencies using micro-/nanochannel junctions and capillary flows.