Surface-adsorption-induced polymer translocation through a nanopore: Effects of the adsorption strength and the surface corrugation

The surface corrugation plays an important role in single polymer diffusion on attractive surfaces. However, its effect on dynamics of surface adsorption-induced polymer translocation through a nanopore is not clear. Using three-dimensional Langevin dynamics simulations, we investigate the dynamics of a flexible polymer chain translocation through a nanopore induced by the selective adsorption of translocated segments onto the trans side of the membrane. The translocation probability $P_{trans}$ increases monotonically, while the mean translocation time $\tau$ has a minimum as a function of the adsorption strength $\varepsilon$, which are explained from the perspective of the effective driving force for the translocation. With the surface being smoother, $\tau$ as well as the scaling exponent $\alpha$ of $\tau$ with the chain length $N$ decreases. Finally, we show that the distributions of the translocation time are non-Gaussian even for strong adsorption at a moderate surface corrugation. A nearly Gaussian distribution of the translocation time is observed only for the smoothest surface we studied.

Figure 1

Schematic representation of a polymer chain of length $N=64$ (a) translocation through a nanopore induced by the selective adsorption of chain segments on the $trans$ side of the membrane (b) adsorbed on the $trans$ side of the membrane just after the translocation.

Figure 2

The translocation probability $P_{trans}$ as a function of the adsorption strength $\varepsilon$ for two different chain lengths $N=64$ and 128.

Figure 3

The mean translocation time $\tau$ as a function of the adsorption strength $\varepsilon$ for two different chain lengths $N=64$ and 128.

Figure 4

The chain length dependence of the mean translocation time $\tau , \tau \sim N^{\alpha }$, at different adsorption strengths.

Figure 5

Influence of the surface corrugation ${\sigma }_{\text{sp}}$ on the mean translocation time $\tau$ for chains of different lengths. The inset shows the dependence of the chain surface diffusion coefficient $D$ on ${\sigma }_{\text{sp}}$. Here, the adsorption strength is kept at $\varepsilon =3.0$.

Figure 6

The scaling behaviors of $\tau \sim N^{\alpha }$ for different surface corrugations ${\sigma }_{\text{sp}}$. The extracted scaling exponent $\alpha$ as a function of ${\sigma }_{\text{sp}}$ is plotted in the inset. Here, the adsorption strength is kept at $\varepsilon =3.0$.

Figure 7

Distributions of the translocation time normalized by their average value $t/\tau$ under (a) different adsorption strengths $\varepsilon$ and (b) different surface corrugations ${\sigma }_{\text{sp}}$. Here, the chain of length is $N=64$.