Electrically powered locomotion of dual-nature colloid-hedgehog and colloid-umbilic topological and elastic dipoles in liquid crystals

TL;DR

This paper demonstrates electrically powered locomotion of colloids in liquid crystals by exploiting their elastic distortions and defect structures, enabling controlled movement through oscillating electric fields.

Contribution

It introduces a novel method to induce and control colloidal motion in liquid crystals using electric fields that manipulate topological defects and elastic distortions.

Findings

Electric fields induce non-reciprocal deformations around colloids.

Oscillating fields cause directed colloid movement.

Reversible defect and distortion dynamics enable controllable locomotion.

Abstract

Colloidal particles in liquid crystals tend to induce topological defects and distortions of the molecular alignment within the surrounding anisotropic host medium, which results in elasticity-mediated interactions not accessible to their counterparts within isotropic fluid hosts. Such particle-induced coronae of perturbed nematic order are highly responsive to external electric fields, even when the uniformly aligned host medium away from particles exhibits no response to fields below the realignment threshold. Here we harness the non-reciprocal nature of these facile electric responses to demonstrate colloidal locomotion. Oscillations of electric field prompt repetitive deformations of the corona of dipolar elastic distortions around the colloidal inclusions, which at appropriately designed electric driving synchronize the displacement directions. We observe the colloid-hedgehog dipole accompanied by an umbilical defect in the tilt directionality field (c-field), along with the texture of elastic distortions that evolves with changing applied voltage. The temporal out-of-equilibrium evolution of the director and c-field distortions around particles upon turning voltage on and off is not invariant upon reversal of time, prompting lateral translations and interactions that markedly differ from what is accessible to these colloids under equilibrium conditions. Our findings may lead to both technological and fundamental science applications of nematic colloids as both model reconfigurable colloidal systems and as mesostructured materials with pre-designed temporal evolution of structure and composition.