Spreading and absorption of a drop on a swelling surface

Abstract

When a drop is placed on a surface it fully wets, it usually spreads until the height of the drop is comparable to the size of a single fluid molecule. However, when some fluid is absorbed by the substrate, the drop will first spread to a given radius before receding and eventually disappearing completely. In this study, we consider the spreading and absorption of a silicone oil drop on a swelling elastomeric substrate. We observe that the maximal radius of the drop does not depend on the fluid viscosity and can be predicted from the droplet volume and material properties. We rationalize our observations with a scaling analysis and a model coupling the spreading to a linear poroelastic description of the elastomer.