Current in a three-dimensional periodic tube with unbiased forces

TL;DR

This paper investigates how Brownian particles move in a three-dimensional asymmetric periodic tube under unbiased forces, revealing how entropic barriers, tube shape asymmetry, and thermal noise influence net current and transport efficiency.

Contribution

It introduces a comprehensive analysis of particle transport in 3D asymmetric tubes considering entropic barriers and unbiased forces, highlighting conditions for current optimization and reversal.

Findings

Net current can be induced by tube shape asymmetry and force asymmetry.

Thermal noise can enhance transport, showing a peaked dependence on temperature.

Optimal bottleneck radius maximizes particle current.

Abstract

Transport of a Brownian particle moving along the axis of a three-dimensional asymmetric periodic tube is investigated in the presence of asymmetric unbiased forces. The reduction of the coordinates may involve not only the appearance of entropic barrier but also the effective diffusion coefficient. It is found that in the presence of entropic barrier, the asymmetry of the tube shape and the asymmetry of the unbiased forces are the two ways of inducing a net current. The current is a peaked function of temperature which indicates that the thermal noise may facilitate the transport even in the presence of entropic barrier. There exists an optimized radius at the bottleneck at which the current takes its maximum value. Competition between the two opposite driving factors may induce current reversal.