Project VII: DNA trapping in counter-rotating flow

In this study, we find a method for trapping DNA molecules using counter-rotating vortices. Our studies predict that the conformation of trapped DNA molecules may be controlled by the flow rate.

At low Peclet number, the DNA molecules are able to extend into the vortices and stretch nearly 100%. At higher Peclet number, the DNA molecules become completely trapped in a small area, allowing extraction.

The physical mechanism behind different trapped DNA conformations depends on the DNA conformation as it enters the stagnation zone. At higher Pe, DNA molecules are compressed as they enter the stagnation zone, leading to nearly complete trapping. At lower Pe, DNA molecules are able to extend out of the stagnation zone as they become trapped.

[1] J.K. Kreft, Y.-L. Chen, and H.-C. Chang, Physical Review E, 77, 030801(R) (2007).