CPIP Seminar: Shaping nanoparticle assemblies at the interface of liquid crystal shells.
Liquid crystals can exhibit spatial patterns in molecular alignment at interfaces that can be reconfigured by external stimuli. This property of anisotropic fluids provides a valuable tool for patterning nanoparticles adsorbed at fluid interfaces, of importance for optical and energy applications. Colloidal particles at the cholesteric liquid crystal interface have been reported to localize either near bulk defects or in regions of favorable surface anchoring. In this work, we demonstrate that both types of ordering can be achieved within the same system. We investigate nanoparticle ordering at the interface of a cholesteric liquid crystal shell in water. The cholesteric stripe patterns on the shell surface are varied in time by thinning the shell thickness via osmotic swelling. By changing these patterns after particle adsorption, particle assemblies on the shell surface can be molded by the underlying elastic fluid to aggregate along discrete lines. The transition of adsorbed particles from surface regions with homeotropic anchoring to regions near defects is accompanied by a reduction in particle mobility. The arrested particle assemblies subsequently prevent topological defects from annealing. These results reveal how liquid crystals can direct the kinetic arrest of interfacial nanoparticles within specific, micron-sized regions by tuning the assembly pathway. Our methods further provide a new approach for mapping out and stabilizing defects in liquid crystals.