Generation and propagation of solitary waves in nematic liquid crystals

TL;DR

This study combines theory, simulations, and experiments to understand how solitary waves form and travel in nematic liquid crystals under AC electric fields, revealing key conditions for soliton generation.

Contribution

It introduces a comprehensive approach to identify conditions for soliton creation in nematic liquid crystals without electrostatic interactions, supported by experimental validation.

Findings

Solitary waves exhibit 'butterfly' or 'bullet' shapes traveling perpendicular to the electric field.

Solitons propagate over long distances without shape loss.

Key conditions include surface imperfections, elastic constant differences, and negative dielectric anisotropy.

Abstract

Solitons in nematic liquid crystals offer intriguing opportunities for transport and sensing in microfluidic systems. Little is known about the elementary conditions that are needed to create solitons in nematic materials. In this work, theory, simulations and experiments are used to study the generation and propagation of solitary waves (or "solitons") in nematic liquid crystals upon the application of an alternating current (AC) electric field. We find that these solitary waves exhibit "butterfly"-like or "bullet"-like structures that travel in the direction perpendicular to the applied electric field. Such structures propagate over long distances without losing their initial shape. The theoretical model adopted here serves to identify some of the key requirements that are needed to generate solitons in the absence of electrostatic interactions. These include surface imperfections that introduce a twist in the director, unequal elastic constants, and negative anisotropic dielectric permittivity. The results of simulations are shown to be in good agreement with our own experimental observations, serving to establish the validity of the theoretical concepts advanced in this work.