Polymer translocation through a nanopore under a pulling force

TL;DR

This study uses Langevin dynamics simulations to analyze how polymer translocation time depends on chain length and pulling force, revealing different regimes and scaling behaviors for wide and narrow pores.

Contribution

It provides a detailed characterization of translocation dynamics under pulling force, including scaling laws and regime transitions, which were not fully understood before.

Findings

Translocation time scales as N^2 with chain length.

Translocation velocity scales as N^{-1}.

Different force regimes exhibit distinct scaling laws for translocation time.

Abstract

We investigate polymer translocation through a nanopore under a pulling force using Langevin dynamics simulations. We concentrate on the influence of the chain length $N$ and the pulling force $F$ on the translocation time $\tau$. The distribution of $\tau$ is symmetric and narrow for strong $F$. We find that $\tau\sim N^{2}$ and translocation velocity $v\sim N^{-1}$ for both moderate and strong $F$. For infinitely wide pores, three regimes are observed for $\tau$ as a function of $F$. With increasing $F$, $\tau$ is independent of $F$ for weak $F$, and then $\tau\sim F^{-2+\nu^{-1}}$ for moderate $F$, where $\nu$ is the Flory exponent, which finally crosses over to $\tau\sim F^{-1}$ for strong force. For narrow pores, even for moderate force $\tau\sim F^{-1}$. Finally, the waiting time, for monomer $s$ and monomer $s+1$ to exit the pore, has a maximum for $s$ close to the end of the chain, in contrast to the case where polymer is driven by an external force within the pore.