Stretchable Superhydrophobicity from Monolithic, Three-Dimensional Hierarchical Wrinkles.

We report the design of three-dimensional (3D) hierarchical wrinkle substrates that can maintain their superhydrophobicity even after being repeatedly stretched. Monolithic poly(dimethysiloxane) with multiscale features showed wetting properties characteristic of static superhydrophobicity with water contact angles (>160°) and very low contact angle hysteresis (<5°). To examine how superhydrophobicity was maintained as the substrate was stretched, we investigated the dynamic wetting behavior of bouncing and splashing upon droplet impact with the surface. On hierarchical wrinkles consisting of three different length scales, superhydrophobic bouncing was observed. The substrate remained superhydrophobic up to 100% stretching with no structural defects after 1000 cycles of stretching and releasing. Stretchable superhydrophobicity was possible because of the monolithic nature of the hierarchical wrinkles as well as partial preservation of nanoscale structures under stretching.