Surface tension and the strain-dependent topography of soft solids

TL;DR

This paper investigates the unexpected increase in small-scale surface topography of soft silicone gels when stretched, revealing a complex interplay between bulk deformation and surface tension effects.

Contribution

It introduces a quantitative, small-strain analysis explaining the counter-intuitive topography growth due to strain-dependent surface tension in soft solids.

Findings

Surface topography increases with stretch in silicone gels.

The response is nearly linear and explained by a small-strain analysis.

Surface tension varies with deformation, affecting surface features.

Abstract

When stretched in one direction, most solids shrink in the transverse directions. In soft silicone gels, however, we observe that small-scale topographical features grow upon stretching. A quantitative analysis of the topography shows that this counter-intuitive response is nearly linear, allowing us to tackle it through a small-strain analysis. We find that the surprising increase of small-scale topography with stretch is due to a delicate interplay of the bulk and surface responses to strain. Specifically, we find that surface tension changes as the material is deformed. This response is expected on general grounds for solid materials, but challenges the standard description of gel- and elastomer-surfaces.