Instability of stretched and twisted soap films in a cylinder

TL;DR

This paper investigates the instability of soap films confined in cylinders when stretched or twisted, revealing a critical aspect ratio beyond which the film breaks down, supported by analysis, simulations, and experiments.

Contribution

It provides a simple analytical framework to predict the critical aspect ratio of soap films under stretching and twisting, validated by experiments and simulations.

Findings

Critical aspect ratio decreases with increasing twist.

Instability occurs due to surface-tension-driven mechanisms.

Analysis matches experimental and simulation results.

Abstract

A soap film, or a flexible membrane without bending and torsional stiffness, that is confined in a cylinder is shown to be susceptible to a surface-tension-driven instability when it is stretched or twisted. This leads to its breakdown and places an upper limit on the aspect ratio of such structures. A simple analysis confirms the values for the critical aspect ratio of the stretched film found in both simulations and experiments on soap films, and this threshold decreases with increasing twist of the film.