The Shape of Inflated Vesicles

TL;DR

This study investigates the shape and scaling properties of self-avoiding fluid vesicles under pressure, revealing a first-order transition and variable fractal shapes characterized by a new scaling exponent.

Contribution

It introduces a detailed analysis of vesicle conformations under pressure, identifying a first-order transition and a novel scaling exponent for inflated vesicle shapes.

Findings

First-order transition from collapsed to inflated phase.

Identification of a new scaling exponent =0.787.

Continuous variation of vesicle shapes with pressure.

Abstract

The conformation and scaling properties of self-avoiding fluid vesicles with zero extrinsic bending rigidity subject to an internal pressure increment $\Delta p>0$ are studied using Monte Carlo methods and scaling arguments. With increasing pressure, there is a first-order transition from a collapsed branched polymer phase to an extended inflated phase. The scaling behavior of the radius of gyration, the asphericities, and several other quantities characterizing the average shape of a vesicle are studied in detail. In the inflated phase, continuously variable fractal shapes are found to be controlled by the scaling variable $x=\Delta p N^{3\nu/2}$ (or equivalently, $y = {<V>}/ N^{3\nu/2}$), where $N$ is the number of monomers in the vesicle and $V$ the enclosed volume. The scaling behavior in the inflated phase is described by a new exponent $\nu=0.787\pm 0.02$.