Gravity-Induced Shape Transformations of Vesicles

TL;DR

This paper theoretically investigates how vesicles with higher-density liquid contents deform under gravity, revealing size-dependent shape transformations, stability of non-axisymmetric forms, and effects of osmotic deflation, relevant for experimental observations.

Contribution

It provides a detailed theoretical analysis of gravity-induced shape changes in vesicles, including stability and collapse mechanisms, which were not comprehensively understood before.

Findings

Large vesicles exhibit stable, non-axisymmetric shapes under gravity.

Osmotic deflation causes vesicles to revert to axisymmetric shapes and collapse.

Size-dependent gravitational energy influences vesicle morphology and phase behavior.

Abstract

We theoretically study the behavior of vesicles filled with a liquid of higher density than the surrounding medium, a technique frequently used in experiments. In the presence of gravity, these vesicles sink to the bottom of the container, and eventually adhere even on non - attractive substrates. The strong size-dependence of the gravitational energy makes large parts of the phase diagram accessible to experiments even for small density differences. For relatively large volume, non-axisymmetric bound shapes are explicitly calculated and shown to be stable. Osmotic deflation of such a vesicle leads back to axisymmetric shapes, and, finally, to a collapsed state of the vesicle.