Effect of solvent viscosity on driven translocation of a semi-flexible chain through a nano-pore

Department of Physics, University of Central Florida - Orlando, FL 32816-2385, USA

Received: 18 October 2017
Accepted: 27 April 2018

Abstract

We study the effect of the solvent viscosity on the translocation dynamics of a semi-flexible polymer through a nano-pore. We use Langevin dynamics (LD) simulation in two dimensions (2D) and demonstrate that at low viscosity a stiffer chain translocates through a nano-pore faster compared to a more flexible chain and that the order of this translocation time is reversed in the high-viscosity regime. Our simulation data shows a non-monotonic dependence of the mean first passage time (MFPT) on solvent viscosity resulting in a minimum in the MFPT at a particular value of the solvent viscosity. The qualitative behavior of the MFPT of the translocating chain above and below this minimum is different. We have found that the value of the solvent viscosity corresponding to this minimum in MFPT depends on chain stiffness, chain length, applied external bias, and pore radius. We provide physically motivating arguments based on the tension propagation (TP) theory of Sakaue and draw an analogy with the Kramers turnover effect for the non-monotonic dependence of MPFT on viscosity.