| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 106 === Many studies have used constant-cross section microchannels with hexagonal post array to separate large DNA fragments. However, it can only achieve a good separation at very low electric field due to the “channeling effect” at high field. To avoid this problem, we combined a divergent channel with post arrays for separating DNA. It was found that a stretched but curved polymer will experience a normal force pushing toward its center of the curvature. Thus, as a stretched DNA passing through a divergent channel, it will migrate towards the curved side wall due to the normal force effect. More importantly, the magnitude of the normal force is related to the length of the DNA. Therefore, we hope to exploit the molecular size dependent normal force to separate DNA.
We used T4 (165.6 kbp) and λ-DNA (48.5 kbp) as the model DNA, and performed experiments with either continuous sample injection or batch sample injection. We recorded both the arrival time of DNA and DNA distribution at the end of the channel. For continuous injection, T4 DNA is subjected to a strong normal force and concentrated at both sides of the channel. Smaller λ-DNA is less affected by the normal force and therefore distributed much more evenly. In this case, the sorting efficiency of T4 DNA can reach 0.57. In the experiments with batch injection, the electrophoresis pathway of T4 DNA was almost completely along the side walls of the channel and the separation efficiency was further increased to 0.85. Because a micro-channel with post arrays can separate DNA in the direction parallel to electric field and a diverging channel can separate DNA in the direction perpendicular to the electric field, our device which combines divergence and post arrays can achieve two-dimensional separation.
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