(379h) Active Motion of Liquid Crystal-in-Liquid Crystal Emulsions

We report on active motion of thermotropic nematic liquid crystal (LCs) droplets dispersed in a continuous nematic phase of a lyotropic chromonic LC (disodium cromoglycate (DSCG)). The continuous phase of DSCG contains surfactant dissolved at a concentration above its critical micellar concentration, resulting in active motion of the LC droplets via interfacial Marangoni flows. In contrast to passive diffusion experiments where the mean square displacements of the LC droplets are greatest in the direction parallel to the DSCG director, we observed largely unidirectional propulsion of active LC droplets in the direction perpendicular to the DSCG director. The unidirectional active motion differs also from past studies of active droplet motion in isotropic continuous phases, for which the direction of propulsion is random. We explain the unidirectional active motion in terms of anisotropic van der Waals interactions that couple the orientation of the LC droplets to the DSCG director. In addition, we quantify the time scale for reorientation of the LC droplet as a function of its size. The unusual dependence of the reorientation time scale with size is explained by the coupling between nematic order and convective flow inside the LC droplets.