The Effect of Shear Flow on the Helfrich Interaction in Lyotropic Lamellar Systems

TL;DR

This paper investigates how shear flow influences the Helfrich interaction in lyotropic lamellar systems, revealing flow-induced anisotropic tension effects that alter membrane fluctuations and can trigger instabilities leading to multilamellar vesicle formation.

Contribution

It introduces a model for shear-induced anisotropic tension affecting Helfrich interactions and predicts potential instabilities in non-permeable membranes.

Findings

Shear flow reduces membrane fluctuations and modifies the compression modulus.

Flow can induce undulatory instabilities in certain membranes.

Potential link between flow-induced instabilities and vesicle transitions.

Abstract

We study the effect of shear flow on the entropic Helfrich interaction in lyotropic surfactant smectic fluids. Arguing that flow induces an effective anisotropic surface tension in bilayers due to a combination of intermonolayer friction, bilayer collisions and convection, we calculate the reduction in fluctuations and hence the renormalised change in effective compression modulus and steady-state layer spacing. We demonstrate that non-permeable or slowly permeating membranes can be susceptible to a undulatory instability of the Helfrich-Hurault type, and speculate that such an instability could be one source of a transition to multilamellar vesicles.