Flexoelectric switching in cholesteric blue phases

TL;DR

This study uses computer simulations to explore how flexoelectric blue phases respond to electric fields, revealing phase transitions, metastable states, and effects of confinement relevant to advanced liquid crystal materials.

Contribution

It demonstrates the field-induced transitions and metastability in flexoelectric blue phases, highlighting effects of confinement and anchoring on their switching behavior.

Findings

Bulk transition from blue phase I to a disclination array along the field

Inability of the system to revert to original blue phase after field removal

Stabilization of new structures under confinement, including disclination loops and splayed patterns

Abstract

We present computer simulations of the response of a flexoelectric blue phase network, either in bulk or under confinement, to an applied field. We find a transition in the bulk between the blue phase I disclination network and a parallel array of disclinations along the direction of the applied field. Upon switching off the field, the system is unable to reconstruct the original blue phase but gets stuck in a metastable phase. Blue phase II is comparatively much less affected by the field. In confined samples, the anchoring at the walls and the geometry of the device lead to the stabilisation of further structures, including field-aligned disclination loops, splayed nematic patterns, and yet more metastable states. Our results are relevant to the understanding of the switching dynamics for a class of new, "superstable", blue phases which are composed of bimesogenic liquid crystals, as these materials combine anomalously large flexoelectric coefficients, and low or near-zero dielectric anisotropy.