| Abstract
| - We study the problem of a field-driven polymer chain of N monomers of size a collidingwith a finite-sized obstacle of radius R in the presence of thermal noise. We show that there are twodifferent mechanisms for chain release from the obstacle: “unhooking” and “rolling off”. The unhookingmechanism is characterized by strong stretching of the chains at release and an unhooking time whichscales with chain length. In contrast, the “rolling-off” mechanism does not impose strong stretching onthe chain conformation and is dependent not upon the size of the chain, but rather upon the size of theobstacle. Thus, macroscopic mobility in an array of small, widely spaced posts provides an opportunity toseparate chains according to their size, while chain mobility in an array of large circular obstacles providesinformation on the size of the obstacles. While important at small time scales, diffusion does not contributesignificantly to the release kinetics from circular obstacles of any size R when the dimensionless fieldstrength, defined as β = Eλa/(kBT) where λ is charge density and E is field strength, is βN > a/R.
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