Mesoscopic Simulation of Electrohydrodynamic Patterns in Positive and Negative Nematic Liquid Crystals

TL;DR

This study uses fully nonlinear simulation to analyze electrohydrodynamic convection patterns in positive and negative nematic liquid crystals, revealing differences in flow dynamics and potential applications in microfluidics.

Contribution

It introduces a modified stochastic rotational model to simulate nonlinear electrohydrodynamic patterns in both types of nematic liquid crystals, advancing beyond previous weakly nonlinear analyses.

Findings

Similar optical convection patterns in reflected polarized light for both LC types

Different flow field driving areas for positive and negative nematic LCs

Potential applications in nematic colloidal transportation in microfluidics

Abstract

For the first time the electrohydrodynamic convection (EHC) of nematic liquid crystals is studied via fully nonlinear simulation. As a system of rich pattern-formation the EHC is mostly studied with negative nematic liquid crystals experimentally, and sometimes with the help of theoretical instability analysis in the linear regime. Up to now there is only weakly nonlinear simulation for a step beyond the emergence of steady convection rolls. In this work we modify the liquid crystal stochastic rotational model (LC SRD) [Lee et al., J. Chem. Phys., 2015, 142, 164110] to incorporate the field alignment mechanism for positive and negative nematic liquid crystals. The convection patterns and their flow dynamics in the presence of external electric field are studied. Our results predict the similar optical convection patterns in the reflected polarized light when one uses positive and negative types of nematic liquid crystals. However in the emerged flow fields, surprisingly, the driving areas of convection rolls are different for different types of LCs. Their application for nematic colloidal transportation in microfluidics is discussed.