Swelling Cholesteric Liquid Crystal Shells to Direct the Assembly of Particles at the Interface

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.

Fluorescence Recovery after Photobleaching in Colloidal Science: Introduction and Application

“…(e) Liquid crystals. Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

“…FRAP shows that the interface is fluid. Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

Anyonic defect braiding and spontaneous chiral symmetry breaking in dihedral liquid crystals

“…4a, right and Movie 5). Such chiral textures are reminiscent of spiral patterns that have recently been observed theoretically and experimentally in cholesteric LCs [46,47]. However, the latter arise from chiral mi-croscopic interactions, while spiral texture patterns in our system arise from a spontaneous symmetry breaking among isotropically interacting achiral particles.…”

Helfrich-Hurault elastic instabilities driven by geometrical frustration

“…The shell thickness can also be varied post-production through osmotic swelling or deswelling, accomplished by changing the concentration of a solute, such as salt or sugar, in the surrounding aqueous phases (Darmon et al, 2016b;Lopez-Leon et al, 2011b;Seč et al, 2012a;Tran et al, 2017;Tu and Lee, 2012). Osmotically swelling the liquid crystal shells is useful for observing the temporal evolution of thickness-or curvature-dependent phenomena (Darmon et al, 2016b;Durey et al, 2020b;Lopez-Leon et al, 2011b;Tran and Bishop, 2020;Urbanski et al, 2017).…”