Topological defect-propelled swimming of nematic colloids

TL;DR

This paper demonstrates how topological defects in nematic fluids can be harnessed to propel colloidal particles, using experiments and simulations to control and analyze their swimming behavior and interactions.

Contribution

It introduces a novel mechanism for active propulsion of colloids via topological defect dynamics in nematic fluids, combining experimental and numerical approaches.

Findings

Defect-driven colloidal swimming can be controlled by magnetic rotation.

Swimmers exhibit anisotropic pair interactions influenced by defect topology.

The work links topological defect dynamics to biomimetic active matter design.

Abstract

Non-equilibrium dynamics of topological defects can be used as a fundamental propulsion mechanism in microscopic active matter. Here, we demonstrate swimming of topological defect-propelled colloidal particles in (passive) nematic fluids through experiments and numerical simulations. Dynamic swim strokes of the topological defects are driven by colloidal rotation in an external magnetic field, causing periodic defect rearrangement which propels the particles. The swimming velocity is determined by the colloid's angular velocity, sense of rotation and defect polarity. By controlling them we can locomote the particles along different trajectories. We demonstrate scattering -- that is, the effective pair interactions -- of two of our defect-propelled swimmers, which we show is highly anisotropic and depends on the microscopic structure of the defect stroke, including the local defect topology and polarity. More generally, this work aims to develop biomimetic active matter based on the underlying relevance of topology.