Director alignment at the nematic-isotropic interface: elastic anisotropy and active anchoring

TL;DR

This study explores how elastic anisotropy influences active anchoring in nematic interfaces, revealing that active anchoring generally dominates over elastic effects except at very low activity levels, affecting interfacial alignment and active length scales.

Contribution

It introduces a multiphase hydrodynamic model incorporating elastic anisotropy to analyze the competition between passive and active anchoring in nematic interfaces.

Findings

Active anchoring dominates at higher activities.

Elastic anisotropy alters the active length scale.

Interfaces remain static at very low activity.

Abstract

Activity in nematics drives interfacial flows that lead to preferential alignment that is tangential or planar for extensile systems (pushers) and perpendicular or homeotropic for contractile ones (pullers). This alignment is known as active anchoring and has been reported for a number of systems and described using active nematic hydrodynamic theories. The latter are based on the one-elastic constant approximation, i.e., they assume elastic isotropy of the underlying passive nematic. Real nematics, however, have different elastic constants, which lead to interfacial anchoring. In this paper, we consider elastic anisotropy in multiphase and multicomponent hydrodynamic models of active nematics and investigate the competition between the interfacial alignment driven by the elastic anisotropy of the passive nematic and the active anchoring. We start by considering systems with translational invariance to analyze the alignment at flat interfaces and, then, consider two-dimensional systems and active nematic droplets. We investigate the competition of the two types of anchoring over a wide range of the other parameters that characterize the system. The results of the simulations reveal that the active anchoring dominates except at very low activities, when the interfaces are static. In addition, we found that the elastic anisotropy does not affect the dynamics but changes the active length that becomes anisotropic.