Toroidal membrane vesicles in spherical confinement

TL;DR

This study explores the equilibrium shapes and topological transitions of toroidal fluid membrane vesicles confined within spherical containers, revealing how size and shape influence membrane morphology and energetics.

Contribution

It provides a detailed phase diagram of toroidal vesicle shapes in spherical confinement and analyzes conditions favoring topology changes.

Findings

Shape transitions depend on scaled area and volume.

Contact with the sphere occurs at specific size thresholds.

Topology change is energetically favored under certain conditions.

Abstract

We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically.