How capillarity affects the propagation of elastic waves in soft gels

TL;DR

This study investigates how capillarity influences elastic wave propagation on soft gel surfaces, revealing that capillarity significantly affects wave behavior at smaller scales than previously thought, with results supported by theoretical and experimental agreement.

Contribution

The paper provides a detailed experimental and theoretical analysis of capillarity's role in elastic wave dispersion on soft gels, highlighting its importance at small wavenumbers.

Findings

Capillarity affects wave dispersion at smaller scales than expected.

Multiple wave modes are observed at the gel surface.

Theoretical predictions align well with experimental data.

Abstract

Elastic waves propagating at the interface of soft solids can be altered by the presence of external forces such as capillarity or gravity. We measure the dispersion relation of waves at the free surface of agarose gels with great accuracy, revealing the existence of multiple modes as well as an apparent dispersion. We disentangle the role of capillarity and elasticity by considering the 3D nature of mechanical waves, achieving quantitative agreement between theoretical predictions and experiments. Notably, our results show that capillarity plays an important role for wavenumbers much smaller than expected from balancing elastic and capillary forces. We further confirm the efficiency of our approach by including the effect of gravity in our predictions and quantitatively comparing it to experiments.