Nematohydrodynamics for Colloidal Self-Assembly and Transport Phenomena

TL;DR

This paper investigates how nematic liquid crystal interactions influence colloidal particle dynamics in microfluidic channels, revealing elastic forces that affect particle movement, aggregation, and potential separation techniques.

Contribution

It introduces a comprehensive analysis of nematic-elastic interactions in microfluidics, highlighting their impact on particle behavior and potential for particle separation.

Findings

Elastic interactions cause size-based particle separation.

Nematic forces induce particle aggregation and reorientation.

Director orientation transitions depend on anchoring strength and particle size.

Abstract

We study colloidal particles in a nematic-liquid-crystal-filled microfluidic channel and show how elastic interactions between the particle and the channel wall lead to different particle dynamics compared with conventional microfluidics. For a static particle, in the absence of a flow field, the director orientation on the particle surface undergoes a rapid transition from uniform to homeotropic anchoring as a function of the anchoring strength and the particle size. In the presence of a flow field, in addition to fluid viscous stresses on the particle, nematic-induced elastic stresses are exerted as a result of the anchoring conditions. The resulting forces are shown to offer the possibility of size-based separation of individual particles. For multi-particle systems, the nematic forces induce inter-particle attraction induces particle attraction, following which the particles aggregate and reorientate. These results illustrate how coupled nematic-hydrodynamic effects can affect the mobility and spatial reorganization of colloidal particles in microfluidic applications.