Surface Elastic Constants of a Soft Solid

TL;DR

This paper measures surface-elastic constants of a soft solid using microscopic observations, enabling prediction of surface stresses under various deformations in the linear-elastic regime.

Contribution

It introduces a method to quantify surface elastic constants of a soft solid through contact-line geometry analysis, which was previously obscured by bulk stresses.

Findings

Two surface-elastic constants measured for a soft polymer gel.

Surface stress dependence on strain characterized.

Method allows prediction of surface stresses for general deformations.

Abstract

Solid interfaces have intrinsic elasticity. However, in most experiments, this is obscured by bulk stresses. Through microscopic observations of the contact-line geometry of a partially wetting droplet on an anisotropically stretched substrate, we measure two surface-elastic constants that quantify the linear dependence of the surface stress of a soft polymer gel on its strain. With these two parameters, one can predict surface stresses for general deformations of the material in the linear-elastic limit.