Hydrogel menisci: Shape, interaction, and instability

Abstract

The interface of a soft hydrogel is easily deformed when it is in contact with particles, droplets or cells. Here we compute the intricate shapes of hydrogel menisci due to the indentation of point particles. The analysis is based on a free energy formulation, by which we also assess the interaction laws between neighbouring particles on hydrogel interfaces, similar to the "Cheerios effect". It is shown how the meniscus formed around the particles results from a competition between surface tension, elasticity and hydrostatic pressure inside the gel. We provide a detailed overview of the various scaling laws, which are governed by a characteristic shear modulus $G^{\ast }=\sqrt{\gamma \rho g}$ that is based on surface tension $\gamma$ and gravity $\rho g$. Stiffer materials exhibit a solid-like response while softer materials are more liquid-like. The importance of $G^{\ast }$ is further illustrated by examining the Rayleigh-Taylor instability of soft hydrogels.

7 pages, 3 figures

References in corpus (4)

• Elastocapillarity: Surface Tension and the Mechanics of Soft Solids
• Gravity driven instability in elastic solids
• Elasto-capillary interaction of particles on the surfaces of ultra-soft gels: a novel route to study self-assembly and soft lubrication
• Elastic Cheerios effect: self-assembly of cylinders on a soft solid

Cited by in corpus (3)

• Printing wet-on-wet: attraction and repulsion of drops on a viscous film
• How capillarity affects the propagation of elastic waves in soft gels
• Ordering of adsorbed rigid rods mediated by the Boussinesq interaction on a soft substrate