Shear-induced structural transitions in confined nematic soft interfaces

Abstract

Research on aqueous-interfaced liquid crystals (LCs) offered valuable outcomes leading to successful applications in sensing and actuation systems. The forward leap of the promising findings in stagnant LC systems will be achieved by the integration of LCs into automated flow systems. In fundamental microfluidics studies, the structural transitions of LC were induced by external fields; yet they were constrained to hard-interfaced flow confinements. In this study, we investigate the structural transitions in flowing nematic LCs confined in microfluidic channels with accessible, stable LC-aqueous soft interfaces. We demonstrate in experiments and in simulations that the applied bulk and interfacial shear significantly transform the director configurations of the nematic LC, due to the anchoring properties at the soft interface. The director profiles, as well as the topology, are influenced substantially by the mechanical stresses induced at the vicinity of the aqueous interfaces depending on the interfacial anchoring conditions, bulk nematic directors, and the direction of the shear. The experimental observations presented herein will guide the ongoing research on the flow of LC in microenvironments and are likely to open new horizons in the development of autonomous platforms including more complex LC phases.