Rheology of an inverted cholesteric droplet under shear flow

TL;DR

This study uses lattice Boltzmann simulations to explore how an inverted cholesteric droplet's rheological behavior varies under shear flow, revealing non-Newtonian to Newtonian-like transitions influenced by shear rate, anchoring, and chirality.

Contribution

It provides new insights into the complex rheological responses of cholesteric droplets under shear, highlighting the roles of shear rate, anchoring strength, and chirality in their dynamics.

Findings

Non-Newtonian behavior at low shear and weak anchoring.

Newtonian-like response at high shear and strong anchoring.

Flow profiles and defect dynamics significantly influence rheology.

Abstract

The dynamics of a quasi two-dimensional isotropic droplet in a cholesteric liquid crystal medium under symmetric shear flow is studied by lattice Boltzmann simulations. We consider a geometry in which the flow direction is along the axis of the cholesteric, as this setup exhibits a significant viscoelastic response to external stress. We find that the dynamics depends upon the magnitude of the shear rate, the anchoring strength of the liquid crystal at the droplet interface and the chirality. While for low shear rate and weak interface anchoring the system shows a non-Newtonian behavior, a Newtonian-like response is observed at high shear rate and strong interface anchoring. This is investigated both by estimating the secondary flow profile, namely a flow emerging along the out-of-plane direction (absent in fully Newtonian fluids, such as water), and by monitoring defect formation and dynamics which alter significantly the rheological response of the system.