Giant Negative Mobility of Janus Particles in a Corrugated Channel

TL;DR

This study uses numerical simulations to explore how elliptic Janus particles move in narrow, rough channels, revealing conditions for giant negative mobility where particles drift against an applied force, enabling efficient control.

Contribution

It introduces the concept of giant negative mobility in Janus particles within rough channels, demonstrating how channel roughness and particle shape influence transport behavior.

Findings

Prolate particles exhibit long ballistic diffusion transients.

Oblate particles show zero diffusion in smooth channels.

Prolate particles can drift against external drive, achieving giant negative mobility.

Abstract

We numerically simulate the transport of elliptic Janus particles along narrow two-dimensional channels with reflecting walls. The self-propulsion velocity of the particle is oriented along either their major (prolate) or minor axis (oblate). In smooth channels, we observe long diffusion transients: ballistic for prolate particles and zero-diffusion for oblate particles. Placed in a rough channel, prolate particles tend to drift against an applied drive by tumbling over the wall protrusions; for appropriate aspect ratios, the modulus of their negative mobility grows exceedingly large (giant negative mobility). This suggests that a small external drive suffices to efficiently direct self-propulsion of rod-like Janus particles in rough channels.