Electroosmotically enabled Electrorheological Effects in a Planar Nematic Crystal Flow

TL;DR

This paper develops a fundamental theory for electroosmotic effects in nematic liquid crystals, analyzing director configurations and flow behavior influenced by electrical double layers at interfaces, with implications for understanding modified flow rheology.

Contribution

It introduces a coupled theoretical framework based on free energy principles to describe potential and director distributions in nematic LCs with induced electrical double layers.

Findings

Multiple stable director configurations identified.

Electroosmotic flow features characterized.

Spontaneous electrorheological effects observed.

Abstract

Study of electrokinetics of nematic liquid crystals (LCs) with dissolved impurities hold utmost importance in understanding director distribution characteristics and modified flow rheology. However, no concrete theory for the non-uniform potential and ionic species distribution, due to an induced electrical double layer (EDL) at the LC-substrate interface, derived from fundamental principles have been put forward in this regard. In this work, we have developed coupled governing equations from fundamental free energy considerations for the potential distribution and the director configuration of the nematic LC within the induced electrical double layer which is generated due to certain physico-chemical interactions at the LC-substrate interface. With these considerations, an electroosmotically-enabled nematodynamics for a particular LC, namely, MBBA, with strong planar anchoring at the boundaries is studied. We obtained multiple solution for director configuration, which is an integral characteristics of nematic flow solutions, and investigated for the most stable solution employing an entropic analysis. We finally proceed to depicts the electroosmotic flow features of the nematic LC wherein we focused on the spontaneous development of the electrorheological effect and the resulting elastic description of the nematic LC for the most stable solution obtained.