Opposite translocation of long and short oligomers through a nanopore

TL;DR

This paper models the translocation of elongated particles like DNA through nanopores, revealing that particle length influences the direction of movement due to complex electrohydrodynamic effects, with potential control via a gate electrode.

Contribution

It introduces a detailed potential energy landscape model showing how particle length affects translocation direction in nanopores, including control mechanisms.

Findings

Net potential energy difference can be opposite for short and long particles.

Thermal noise causes biased diffusion in opposite directions.

Gate electrodes can control the length at which transport reverses.

Abstract

We consider elongated cylindrical particles, modeling e.g. DNA fragments or nano-rods, while translocating under the action of an externally applied voltage through a solid state nanopore. Particular emphasis is put on the concomitant potential energy landscape, encountered by the particle on its passage through the pore due to the complex interplay of various electrohydrodynamic effects beyond the realm of small Debye lengths. We find that the net potential energy difference across the membrane may be of opposite sign for short and long particles of equal diameters and charge densities (e.g. oligomers). Thermal noise thus leads to biased diffusion through the pore into opposite directions. By means of an additional membrane gate electrode it is even possible to control the specific particle length at which this transport inversion occurs.