THESIS
2006
xvii, 146 leaves : ill. ; 30 cm
Abstract
A novel high-throughput technology approach for the design and fabrication of a capillary electrophoresis microsystem integrated with sub-micron pillar arrays is developed in this work. Featuring a dual-photolithography step, the technology replaces the commonly used complicated fabrication process based on electron-beam lithography by a sequence of projection and contact photolithography. In this manner, the time needed for the sub-micron pillar pattern generation is dramatically shortened and a high flexibility in the integration of different pillar patterns into various microsystems is ensured. Combining with an in-house-developed deep-reactive-ion-etching recipe, very high aspect-ratio sub-micron pillars embedded in a standard microfluidic device can be obtained to facilitate device...[
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A novel high-throughput technology approach for the design and fabrication of a capillary electrophoresis microsystem integrated with sub-micron pillar arrays is developed in this work. Featuring a dual-photolithography step, the technology replaces the commonly used complicated fabrication process based on electron-beam lithography by a sequence of projection and contact photolithography. In this manner, the time needed for the sub-micron pillar pattern generation is dramatically shortened and a high flexibility in the integration of different pillar patterns into various microsystems is ensured. Combining with an in-house-developed deep-reactive-ion-etching recipe, very high aspect-ratio sub-micron pillars embedded in a standard microfluidic device can be obtained to facilitate device operation.
The influence of the embedded sub-micron pillars inside microchannels on DNA electrokinetics is studied. The pillars were experimentally identified to affect DNA motion patterns and numerically verified to re-distribute the electric field arrangement, leading to a variation in the measured DNA migration velocity inside different pillar arrays.
The developed capillary electrophoresis microsystem is successfully applied for DNA separations with merely a free buffer solution, as well as various DNA electrophoretic velocity measurements. A nonlinear dependence of DNA electrophoretic velocity on electric field strength is observed. This is due to distinct molecular DNA behaviours under varying field strengths. Electrophoretic velocity dependence on DNA size is also examined. Small DNA molecules are observed to pass through the pillar array in an almost unperturbed manner, resulting in a large migration velocity in electric fields of varying strengths. Migration velocities of medium-sized DNA and large DNA are more complicated and their relative speed is field dependent, similar to the “band inversion” phenomenon in conventional gel electrophoresis. Electrophoretic velocity dependence on pillar spacing is investigated as well. In the cases of large spacing, the DNA velocity decreases with increasing pillar spacing, due to the electric field re-distribution caused by the embedded pillars. On the other hand, when pillars are closely packed, additional entropy effect emerges and the resultant DNA velocity is a complex product of different effects. Correlation of the experimental results to electrophoresis models suggests that DNA electrokinetic behaviour in a capillary electrophoresis microsystem integrated with sub-micron pillar arrays is more appropriately described by the Biased Reptation with Fluctuations model.
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