High-throughput design and fabrication of an integrated microsystem with high aspect-ratio sub-micron pillar arrays for free-solution micro capillary electrophoresis

Abstract

A new technology approach for the design, fabrication and application of an integrated free-solution capillary electrophoresis microsystem is presented. Combining the advantages of projection, contact photolithography and deep-reactive-ion-etching, this approach allows fast and flexible formation of micron-sized channels integrated with extremely high aspect-ratio (>50:1) sub-micron pillar arrays on a silicon substrate. Utilizing fluorescence video microscopy, free-solution DNA separation has been demonstrated. Furthermore, the detailed DNA molecular interaction with the pillars inside the microsystem can be analysed. In comparison with the previously reported fabrication technologies, such as electron beam lithography, the newly presented technology approach offers a significant improvement in fabrication time and design flexibility; both are highly desirable not only for potential commercialization of the free-solution electrophoresis microsystem in applications such as lab-on-a-chip but also for systematic studies of micro-scale DNA kinetics.

Electrophoretic collision of a DNA molecule with a small elliptical obstacle

“…Following release, the DNA relaxes back to the coiled form in preparation for the next collision event. The post collision process forms the basis for a number of microfluidic and nanofluidic separation devices [4][5][6][7][8], since the nominal unhooking time scales linearly with molecular weight [2].…”

Experimental study of the effect of disorder on DNA dynamics in post arrays during electrophoresis

“…Two dimensional arrays of micron-sized cylindrical posts are proven to rapidly separate long DNA under a dc electric field [1][2][3][4][5][6][7][8]. While the application of a dc electric field using the standard separation matrices (polyacrylamide or agarose gels) fails to produce a size dependent mobility for long DNA ( > ∼ 10 kbp) [9], the increased pore size of microfabricated arrays results in a size dependent mobility for long DNA.…”

Tilted post arrays for separating long DNA

“…3 Unfortunately, due to the slow migration of long DNA in the net direction of the applied field, pulsed field separations take hours to days to achieve a baseline separation; 3 this time is compared to minutes needed to separate long DNA in post arrays. [4][5][6] Regular arrays of micro-and nano-sized posts, fabricated by semiconductor methods, have been the subject of substantial experimental work [6][7][8][9][10][11][12][13][14][15][16][17][18][19] using a wide variety of materials, post sizes, and post spacing. In addition to microfabricated arrays with perfectly ordered features, results also exist for self-assembled magnetic beads, 4,5,20 which form quasihexagonal arrays, microfabricated arrays with intentional disorder, 21 and nanowire-based posts.…”