Influence of Capillary Flow on Self-Organization of Water Droplets in Nematic Liquid Crystal

Abstract

The results of studying the motion of isotropic liquid drops in a homeotropic layer of liquid crystal Е7 with long-lived instabilities induced by a damped shear flow that occurs when a flat capillary is filled due to the action of capillary forces (capillary flow). An intense flow of nematics with initial homeotropic orientation leads to the appearance of orientational instabilities. In the experiments, a liquid-crystal cell with a variable gap (from 60 to 100 μm) was used. The object of the study was a 10:1 emulsion "liquid crystal – isotropic liquid". It was found that drops of isotropic liquid form various types of spatial structures. In particular, chains of drops in the region of strong deformations of LC orientation (for example, at the boundaries of the existence of long-lived regions with a changed orientation) were observed. In addition, an increased concentration of isotropic droplets occurred in the region separating the sections of the liquid crystal under the action of an electric field and in the absence of its action. Based on the analysis of microscopic images, the velocity of mutual motion of two isolated drops was determined. It made possible to estimate the interaction force between the drops (Fa = 5.6 pN) that was caused by the distortions of orientational structure in the vicinity of the drops. The results obtained are discussed within the existing theory of liquid crystals.