Motion by Stopping: Rectifying Brownian Motion of Non-spherical Particles

TL;DR

This paper demonstrates that non-spherical particles in non-equilibrium conditions can exhibit directed, controllable motion through a novel stopping mechanism, challenging traditional symmetry assumptions in Brownian motion.

Contribution

It introduces a new method to induce directed motion in non-spherical particles by periodic stopping, supported by simulations and analytical models.

Findings

Directed motion achieved without ratchet potentials or temperature gradients.

Particle shape controls the direction of motion via tensorial Minkowski functionals.

Motion can occur against fluid drift in non-equilibrium conditions.

Abstract

We show that Brownian motion is spatially not symmetric for mesoscopic particles embedded in a fluid if the particle is not in thermal equilibrium and its shape is not spherical. In view of applications on molecular motors in biological cells, we sustain non-equilibrium by stopping a non-spherical particle at periodic sites along a filament. Molecular dynamics simulations in a Lennard-Jones fluid demonstrate that directed motion is possible without a ratchet potential or temperature gradients if the asymmetric non-equilibrium relaxation process is hindered by external stopping. Analytic calculations in the ideal gas limit show that motion even against a fluid drift is possible and that the direction of motion can be controlled by the shape of the particle, which is completely characterized by tensorial Minkowski functionals.