Switching dynamics in cholesteric blue phases

TL;DR

This study numerically investigates the switching behavior and hydrodynamics of blue phase I and II in cholesteric liquid crystals under electric fields, revealing different regimes and metastability related to disclination network reorganization.

Contribution

It provides new insights into the dynamic switching processes and stability of blue phases in liquid crystals, including effects of boundary conditions and field orientation.

Findings

Blue phases exhibit three distinct regimes under electric fields.

BPII can recover its structure after field removal, unlike BPI.

Switching involves significant reorganization of disclination networks.

Abstract

Blue phases are networks of disclination lines, which occur in cholesteric liquid crystals near the transition to the isotropic phase. They have recently been used for the new generation of fast switching liquid crystal displays. Here we study numerically the steady states and switching hydrodynamics of blue phase I (BPI) and blue phase II (BPII) cells subjected to an electric field. When the field is on, there are three regimes: for very weak fields (and strong anchoring at the boundaries) the blue phases are almost unaffected, for intermediate fields the disclinations twist (for BPI) and unzip (for BPII), whereas for very large voltages the network dissolves in the bulk of the cell. Interestingly, we find that a BPII cell can recover its original structure when the field is switched off, whereas a BPI cell is found to be trapped more easily into metastable configurations. The kinetic pathways followed during switching on and off entails dramatic reorganisation of the disclination networks. We also discuss the effect of changing the director field anchoring at the boundary planes and of varying the direction of the applied field.