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Over the past 15 years, research in the field of microfluidics has rapidly gained popularity. By seeking to miniaturize and automate separation-based analysis, microfluidic research seeks to improve current methods through decreased cost, analysis time, and sources of contamination. My work has focused on developing a novel fabrication method, based on standard microfabrication techniques, to create thin-film microfluidic devices. This microfabrication format makes it possible to generate devices that provide high efficiencies, enable mass fabrication, and provide a platform capable of integrating the microfluidic and electronic components necessary for a micro-total analysis system (μ-TAS). Device fabrication combines the processes of photolithography, thermal evaporation, plasma enhanced chemical vapor deposition (PECVD), and wet chemical etching to ultimately provide hollow-core channels. When these microcapillaries are filled with buffer and potentials are applied across them, control of the flow in the channels can be established. By designing intersecting microchannels having an offset “T†geometry, I have been able to inject and electrophoretically separate three fluorescently labeled amino acids and obtain efficiencies of over 2500 theoretical plates. Through the addition of commercially available electroosmotic flow reducing coatings, I have been able to improve the separation of these amino acids, decreasing the run time by approximately 6 fold and increasing the efficiency by as much as 10 fold. Through the use of these coatings I have also been able to carry out electrophoretic separations of three peptides. My most recent work has focused on the polymerization of acrylamide gels in these channels. A method for the selective placement of a gel has been developed using a prepolymer solution with a light-sensitive initiator. Further work to adjust the polymer pore size and interface with ampholyte-containing gels should allow methods such as capillary gel electrophoresis (CGE), preconcentration, and two dimensional (isolectric focusing and CGE) separations to be performed. The development of gel-based analysis methods, along with other fluidic and electrical capacities, should move thin-film microdevices toward the realization of the lab-on-a-chip concept. |
