Elastocapillary lifting and encapsulation of water by a triangular elastic film under gravity

TL;DR

This study explores how thin elastic triangular films can encapsulate water through a balance of surface, gravitational, and bending energies, revealing conditions for stable encapsulation.

Contribution

It introduces a physical criterion for water encapsulation by elastic films based on energy competition, supported by systematic experiments with varying film parameters.

Findings

Encapsulation occurs at a narrow parameter region where elastocapillary, elastogravity, and capillary length scales intersect.

Three distinct morphologies observed: folding, recoiling, and encapsulation.

Encapsulation is governed by a balance of bending, capillary, and gravitational energies.

Abstract

We investigate the encapsulation of water by a thin elastic film as a minimal model of elastocapillary self-folding with fluid transport. An equilateral triangular polydimethylsiloxane film is lifted quasi-statically from a water surface, while its side length and thickness are systematically varied. Depending on these parameters, the film exhibits three distinct morphologies: folding, recoiling, and liquid encapsulation. We show that the observed morphology is selected by the competition between surface energy, gravitational energy of the liquid, and bending energy of the film. In particular, encapsulation occurs in a narrow parameter region corresponding to the intersection of the elastocapillary, elastogravity, and capillary length scales. This result provides a simple physical criterion for liquid encapsulation by elastic films, based on the balance of bending, capillary, and gravitational energies.