Phase behavior of a nematic liquid crystal in contact with a chemically and geometrically structured substrate

TL;DR

This study explores how a nematic liquid crystal's phase behavior is influenced by chemically and geometrically patterned substrates, revealing complex phase diagrams and bistability relevant for device applications.

Contribution

It provides a detailed analysis of phase transitions and stability in nematic liquid crystals on structured surfaces, combining chemical and geometric effects within the Frank--Oseen model.

Findings

Rich phase diagrams with homeotropic, planar, and tilted textures

Groove depth and anchoring strength significantly affect phase transitions

Demonstrates bistability in a nematic device configuration

Abstract

A nematic liquid crystal in contact with a grating surface possessing an alternating stripe pattern of locally homeotropic and planar anchoring is studied within the Frank--Oseen model. The combination of both chemical and geometrical surface pattern leads to rich phase diagrams, involving a homeotropic, a planar, and a tilted nematic texture. The effect of the groove depth and the anchoring strengths on the location and the order of phase transitions between different nematic textures is studied. A zenithally bistable nematic device is investigated by confining a nematic liquid crystal between the patterned grating surface and a flat substrate with strong homeotropic anchoring.