Swelling cholesteric liquid crystal shells to direct colloids at the interface

TL;DR

This paper demonstrates how osmotic swelling of cholesteric liquid crystal shells can direct colloidal assembly into stable, defect-mapped patterns by controlling the interplay of surface and bulk energies, highlighting the role of kinetic pathways.

Contribution

It introduces a dynamic method to control colloidal assembly on cholesteric shells via swelling, enabling the formation of defect-stabilized, patterned colloidal structures.

Findings

Colloidal particles can be repositioned from surface to defect regions during swelling.

Particle mobility decreases as they transition to defect regions.

Stable colloidal patterns map topological defects in cholesterics.

Abstract

Cholesteric liquid crystals can exhibit spatial patterns in molecular alignment at interfaces that can be exploited for particle assembly. These patterns emerge from the competition between bulk and surface energies, tunable with the system geometry. In this work, we use the osmotic swelling of cholesteric double emulsions to assemble colloidal particles through a pathway-dependent process. Particles can be repositioned from a surface-mediated to an elasticity-mediated state through dynamically thinning the cholesteric shell at a rate comparable to that of colloidal adsorption. By tuning the balance between surface and bulk energies with the system geometry, colloidal assemblies on the cholesteric interface can be molded by the underlying elastic field to form linear aggregates. The transition of adsorbed particles from surface regions with homeotropic anchoring to defect regions is accompanied by a reduction in particle mobility. The arrested assemblies subsequently map out and stabilize topological defects. These results demonstrate the kinetic arrest of interfacial particles within definable patterns by regulating the energetic frustration within cholesterics. This work highlights the importance of kinetic pathways for particle assembly in liquid crystals, of relevance to optical and energy applications.