Viral nematics in confined geometries

TL;DR

This paper theoretically investigates how nematic liquid crystals, modeled after rod-like viruses, form various stable and unstable configurations within confined circular and annular geometries, emphasizing the role of defects and surface anchoring.

Contribution

It provides an analytical framework showing boundary defects are more stable than bulk defects and explores symmetry breaking in nematic textures under confinement without fitting parameters.

Findings

Bulk defects are unstable compared to boundary defects.

Nematic textures with boundary defects are stable in annular geometries.

Symmetry breaking mechanisms lead to specific nematic textures.

Abstract

Motivated by recent experiments on the rod-like virus bacteriophage fd, confined to circular and annular domains, we present a theoretical study of structural transitions in these geometries. Using the continuum theory of nematic liquid crystals, we examine the competition between bulk elasticity and surface anchoring, mediated by the formation of topological defects. We show analytically that bulk defects are unstable with respect to defects sitting at the boundary. Moreover, in case of an annulus, whose topology does not require the presence of topological defects, under weak anchoring conditions we find that nematic textures with boundary defects are stable compared to the defect free configurations. Thus our simple approach, with no fitting parameters, suggests a possible symmetry breaking mechanism responsible for the formation of one-, two- and three-fold textures under annular confinement.