Flow-induced currents in nanotubes: a Brownian dynamics approach

TL;DR

This study uses Brownian dynamics simulations to explore how flow fields induce unidirectional drift in particles within nanotube-like channels, revealing dependencies on shear rate, channel width, and particle interactions.

Contribution

It introduces a numerical approach to analyze flow-induced currents in nanotubes, highlighting how flow conditions and particle interactions influence particle drift and fluctuations.

Findings

Flow induces unidirectional drift in confined particles.

Drift velocity depends on shear rate and channel width.

Reversing interspecies interactions affects flow-rate thresholds and fluctuations.

Abstract

Motivated by recent experiments [Science {\bf 299}, 1042 (2003)] reporting that carbon nanotubes immersed in a flowing fluid displayed an electric current and voltage, we numerically study the behaviour of a collection of Brownian particles in a channel, in the presence of a flow field applied on similar but slower particles in a wide chamber in contact with the channel. For a suitable range of shear rates, we find that the flow field induces a unidirectional drift in the confined particles, and is stronger for narrower channels. The average drift velocity initially rises with increasing shear rate, then shows saturation for a while, thereafter starts decreasing, in qualitative agreement with recent theoretical studies [Phys. Rev. B {\bf 70}, 205423 (2004)] based on Brownian drag and ``loss of grip''. Interestingly, if the sign of the interspecies interaction is reversed, the direction of the induced drift remains the same, but the flow-rate at which loss of grip occurs is lower, and the level of fluctuations is higher.