Controlling motile disclinations in a thick nematogenic material with an electric field

Amit Kumar Bhattacharjee

doi:10.1038/s41598-018-19891-0

Abstract

Manipulating topological disclination networks that arise in a symmetry-breaking phase transformation in widely varied systems including anisotropic materials can potentially lead to the design of novel materials like conductive microwires, self-assembled resonators, and active anisotropic matter. However, progress in this direction is hindered by a lack of control of the kinetics and microstructure due to inherent complexity arising from competing energy and topology. We have studied thermal and electrokinetic effects on disclinations in a three-dimensional nonabsorbing nematic material with a positive and negative sign of the dielectric anisotropy. The electric flux lines are highly nonuniform in uniaxial media after an electric field below the Fréedericksz threshold is switched on, and the kinetics of the disclination lines is slowed down. In biaxial media, depending on the sign of the dielectric anisotropy, apart from the slowing down of the disclination kinetics, a nonuniform electric field filters out disclinations of different topology by inducing a kinetic asymmetry. These results enhance the current understanding of forced disclination networks and establish the presented method, which we call fluctuating electronematics, as a potentially useful tool for designing materials with novel properties in silico.

Highlights

Topological singularities such as points, lines and walls are ubiquitous in phases with broken symmetry
It is interesting to examine whether locally uniform and nonuniform electric field can lead to a time-dilated kinetics of the disclination network[13], and, how the anisotropy of the nematic orientation embedded in the dielectric tensor leads to nonuniformity in the local electric field
By investigating beyond the uniform field assumption[27], in this article, we have developed a fluctuating electronematics method based on the thermal description of the Ginzburg-Landau-de Gennes (GLdG) theory, with the physical control over the role of each forcing to accurately describe thermal and electrokinetic phenomena in three dimensional nematic liquid crystals (NLC) media

Summary

Introduction

Topological singularities such as points, lines and walls are ubiquitous in phases with broken symmetry. Of complexity, (a) free from numerical artifacts of the traditional methods[23], accounts for (b) local nonuniformity in electric field and (c) equilibrium thermal fluctuations by respecting physical laws, (d) guarantees zero-trace property of the orientation tensor and (e) incorporates anisotropic elasticity to probe beyond the single diffusion (one elastic constant) approximation[23].

Results

Conclusion