Liquid crystal microfluidics: surface, elastic and viscous interactions at microscales

The hydrodynamic properties of nematic liquid crystals are characterized by a complex mutual coupling between flow, viscosity, and nematic order. While the flow behaviour of nematic bulk samples is well known, corresponding studies in microfluidic settings are still at an early stage. The presence of the four confining channel walls – and in particular the nature of the surface anchoring of the nematic order on the walls – adds new phenomena to the already rich and multifaceted flow behaviour. We present an overview of recent studies focusing on the microfluidics of nematic liquid crystals. Particular topics are the functionalization of the channel walls for defined surface anchoring conditions and the resulting structures of the nematic director field, the controlling and tuning of the flow velocity profile and director field configuration and resulting opto-fluidic applications, and the behaviour of topological defects in the flowing nematic and their application for a guided colloidal transport.