Mechanochemical Active Ratchet

TL;DR

This paper presents a mechanism for controlling the direction of nanoswimmers using a ratchet potential, transforming velocity fluctuations into a net current, with implications for nanoscale motor design.

Contribution

It introduces a thermodynamically consistent model showing how chemical-mechanical coupling in active particles can be harnessed for directed motion using ratchet potentials.

Findings

Net current depends on ratchet amplitude and periodicity.

Transverse force can trigger directed motion.

Model emphasizes importance of chemical reaction modeling in active matter.

Abstract

Self-propelled nanoparticles moving through liquids offer the possibility of creating advanced applications where such nanoswimmers can operate as artificial molecular-sized motors. Achieving control over the motion of nanoswimmers is a crucial aspect for their reliable functioning. While the directionality of micron-sized swimmers can be controlled with great precision, steering nano-sized active particles poses a real challenge. One of the reasons is the existence of large fluctuations of active velocity at the nanoscale. Here, we describe a mechanism that, in the presence of a ratchet potential, transforms these fluctuations into a net current of active nanoparticles. We demonstrate the effect using a generic model of self-propulsion powered by chemical reactions. The net motion along the easy direction of the ratchet potential arises from the coupling of chemical and mechanical processes and is triggered by a constant, transverse to the ratchet, force. The current magnitude sensitively depends on the amplitude and the periodicity of the ratchet potential and the strength of the transverse force. Our results highlight the importance of thermodynamically consistent modeling of chemical reactions in active matter at the nanoscale and suggest new ways of controlling dynamics in such systems.