Viscoelasticity of two-layer-vesicles in solution

TL;DR

This paper investigates the dynamic shape relaxation and viscoelastic properties of two-layer vesicles in solution, revealing how gap size influences relaxation modes and shear response, with implications for understanding complex fluid behavior.

Contribution

It introduces a detailed analysis of shape relaxation modes and viscoelasticity in two-layer vesicles, highlighting the impact of bilayer gap on relaxation dynamics and shear response.

Findings

Fast and slow relaxation modes depend on bilayer gap size.

Complex viscosity is dominated by the fast mode at small gaps.

Crossover gap depends on bilayer interactions, enabling amplitude switching observations.

Abstract

The dynamic shape relaxation of the two-layer-vesicle is calculated. In additional to the undulation relaxation where the two bilayers move in the same direction, the squeezing mode appears when the gap between the two bilayers is small. At large gap, the inner vesicle relaxes much faster, whereas the slow mode is mainly due to the outer layer relaxation. We have calculated the viscoelasticity of the dilute two-layer-vesicle suspension. It is found that for small gap, the applied shear drives the undulation mode strongly while the slow squeezing mode is not much excited. In this limit the complex viscosity is dominated by the fast mode contribution. On the other hand, the slow mode is strongly driven by shear for larger gap. We have determined the crossover gap which depends on the interaction between the two bilayers. For a series of samples where the gap is changed systematically, it is possible to observe the two amplitude switchings.