Elastocapillary adhesion of a soft cap on a rigid sphere.

We study the capillary adhesion of a spherical elastic cap on a rigid sphere of a different radius. Caps of small area accommodate the combination of flexural and in-plane strains induced by the mismatch in curvature, and fully adhere to the sphere. Conversely, wider caps delaminate and exhibit only partial contact. We determine the maximum size of the cap enabling full adhesion and describe its dependence on experimental parameters through a balance of stretching and adhesion energies. Beyond the maximum size, complex adhesion patterns such as blisters, bubbles or star shapes are observed. We rationalize these different states in configuration diagrams where stretching, bending and adhesion energies are compared through two dimensionless parameters.

Marangoni Bursting: Evaporation-Induced Emulsification of Binary Mixtures on a Liquid Layer.

Adjusting the wetting properties of water through the addition of a miscible liquid is commonly used in a wide variety of industrial processes involving interfaces. We investigate experimentally the evolution of a drop of water and volatile alcohol deposited on a bath of oil: The drop spreads and spontaneously fragments into a myriad of minute droplets whose size strongly depends on the initial concentration of alcohol. Marangoni flows induced by the evaporation of alcohol play a key role in the overall phenomenon. The intricate coupling of hydrodynamics, wetting, and evaporation is well captured by analytical scaling laws. Our scenario is confirmed by experiments involving other combinations of liquids that also lead to this fascinating phenomenon.