Confined Brownian ratchets

TL;DR

This paper investigates how confinement influences Brownian ratchets, revealing cooperative effects that enable directed transport and potential applications in nanoscale device engineering.

Contribution

It introduces a unified analysis of confined Brownian ratchets using an entropic potential framework, highlighting novel cooperative rectification mechanisms.

Findings

Confinement induces strong cooperativity between ratchet mechanisms and entropic bias.

Net transport can occur even when individual mechanisms do not produce rectification.

The results suggest new methods for controlling nanoscale transport and segregation.

Abstract

We analyze the dynamics of Brownian ratchets in a confined environment. The motion of the particles is described by a Fick-Jakobs kinetic equation in which the presence of boundaries is modeled by means of an entropic potential. The cases of a flashing ratchet, a two-state model and a ratchet under the influence of a temperature gradient are analyzed in detail. We show the emergence of a strong cooperativity between the inherent rectification of the ratchet mechanism and the entropic bias of the fluctuations caused by spatial confinement. Net particle transport may take place in situations where none of those mechanisms leads to rectification when acting individually. The combined rectification mechanisms may lead to bidirectional transport and to new routes to segregation phenomena. Confined Brownian ratchets (CBR) could be used to control transport in mesostructures and to engineer new and more efficient devices for transport at the nanoscale.