Mesoscale Structure of Chiral Nematic Shells

TL;DR

This study uses the Landau-de Gennes method to analyze how chirality and shell geometry influence defect structures in nematic liquid crystal shells, revealing phase transitions and potential sensor applications.

Contribution

It provides a detailed phase diagram of defect structures in chiral nematic shells and explores the effects of thickness heterogeneity and chirality on defect positions.

Findings

Identification of phase transitions between defect structures

Chirality influences defect positions and shell behavior

Thickness heterogeneity affects core positioning

Abstract

There is considerable interest in understanding and controlling topological defects in nematic liquid crystals (LCs). Confinement, in the form of droplets, has been particularly effective in that regard. Here, we employ the Landau-de Gennes method to explore the geometrical frustration of nematic order in shell geometries, and focus on chiral materials. By varying the chirality and thickness in uniform shells, we construct a phase diagram that includes tetravalent structures, bipolar structures (BS), bent structures and radial spherical structures (RSS). It is found that, in uniform shells, the BS-to-RSS structural transition, in response to both chirality and shell geometry, is accompanied by an abrupt change of defect positions, implying a potential use for chiral nematic shells as sensors. Moreover, we investigate thickness heterogeneity in shells and demonstrate that non-chiral and chiral nematic shells exhibit distinct equilibrium positions of their inner core that are governed by shell chirality c.