Biopolymer filtration in corrugated nanochannels
  We examine pressure-driven non-equilibrium transport of linear, circular and star polymers through a nanochannel containing a rectangular pit with full hydrodynamic interactions and thermal fluctuations. We demonstrate that with sufficiently small pressure differences, there is contour length-dependent entropic trapping of the polymer in the pit when the pit and the polymer sizes are compatible. This is due to competition between flow and chain relaxation in the pit, which leads to a non-monotonic dependence of the polymer mobility on its size and should aid in the design of nanofiltration devices based on the polymer size and shape. 
Santtu T.T. Ollila, Colin Denniston, Mikko Karttunen, Tapio   Ala-Nissila
cond-mat.soft