Switching hydrodynamics in multi-domain, twisted nematic, liquid crystal devices

TL;DR

This paper investigates the switching dynamics of multi-domain twisted nematic liquid crystal devices, focusing on disclination line behavior and proposing design improvements for faster switching speeds.

Contribution

It provides a numerical analysis of disclination dynamics in two- and four-domain devices, explaining switching behaviors and suggesting improved device designs.

Findings

Disclination line motion governs switching speed.

Two-domain devices switch off slowly due to disclination dynamics.

Proposed design modifications improve switching performance.

Abstract

We study the switching dynamics in two-domain and four-domain twisted nematic liquid crystal devices. The equilibrium configuration of these devices involves the coexistence of regions characterised by different handedness of the inherent director twist. At the boundaries between these regions there are typically disclinations lines. The dynamics of the disclination lines controls the properties, and in particular the switching speed, of the devices. We describe their motion using a numerical solution of the Beris-Edwards equations of liquid crystal hydrodynamics. Hence we are able to explain why a conventional two-domain device switches off slowly and to propose a device design which circumvents this problem. We also explain the patterns of disclination creation and annihilation that lead to switching in the four-domain twisted nematic device.