Structure formation of surfactant membranes under shear flow

TL;DR

This study uses numerical simulations to explore how surfactant membranes form and transform under shear flow, revealing various structures and instabilities that depend on shear rate and membrane volume fraction.

Contribution

It introduces a meshless-membrane model combined with particle-based hydrodynamics to simulate shear-induced structure formation in surfactant-water mixtures.

Findings

Low shear rates produce vesicles and lamellae.

High shear rates cause undulation instability and rolled structures.

Simulated structures match experimental scattering data.

Abstract

Shear-flow-induced structure formation in surfactant-water mixtures is investigated numerically using a meshless-membrane model in combination with a particle-based hydrodynamics simulation approach for the solvent. At low shear rates, uni-lamellar vesicles and planar lamellae structures are formed at small and large membrane volume fractions, respectively. At high shear rates, lamellar states exhibit an undulation instability, leading to rolled or cylindrical membrane shapes oriented in the flow direction. The spatial symmetry and structure factor of this rolled state agree with those of intermediate states during lamellar-to-onion transition measured by time-resolved scatting experiments. Structural evolution in time exhibits a moderate dependence on the initial condition.