Ultra-soft textured substrates

Droplets deposited on soft elastomers or gels with elastic moduli ~ 1 – 10 kPa induce a micron-scale elastic deformation at the contact line. This significantly modifies the wetting properties of the solid - for example, a droplet deposited on an inclined soft surface will slide downward driven by its weight at velocities orders of magnitude less than a droplet on a similarly inclined rigid solid. Here, we confine the contact between water and a soft silicone gel to micrometric patches by texturing the solid, inducing superhydrophobicity for materials with elastic moduli as low as 3 kPa. The coupling between surface texture and surface compliance strongly influences the behavior of the droplet at both macro- and micro- scales, leading to a giant speed up during descent, and potentially affecting the stability of the Cassie state.