Drop spreading on soft textiles*

In many situations, drops spread on soft and porous substrates, such as paper, wood or woven fabrics. Here, we consider model systems to characterize the coupling between spreading, absorption and deformation of the substrate. When a wetting drop is deposited on a mesh, it does not fully spreads but adopts a compact shape that conforms to the underlying fibrous structure. The drop reaches a maximum radius that increases with decreasing porosity, and is given by a balance between the surface energy gained by wetting the material and the cost of energy associated with the creation of liquid- air interfaces. When the mesh is soft, its elements may deform and collapse due to capillary forces. Furthermore, on a poroelastic mesh, this spreading is coupled with a fast absorption that leads to strong out-of-plane deformations of the thin substrate. We characterize this spreading and swelling dynamics and show that it strongly depends on the geometry of the meshes, in particular on the anisotropy of the pattern.