Mechanically switchable wetting on wrinkled elastomers with dual-scale roughness

We report the fabrication of a new superhydrophobic surface with dual-scale roughness by coating silica nanoparticles on a poly(dimethylsiloxane) (PDMS) elastomer bilayer film with micro-scaled ripples. The wetting behavior of the surface can be reversibly tuned by applying a mechanical strain, which induces the change in micro-scale roughness determined by the ripples. The dual-scale roughness promotes the wetting transition of the final dual-structure surface from Wenzel region into the Cassie region, thus, reducing the sliding angle at least three times in comparison to that from the surfaces with single-scale roughness (either from the nanoparticle film or the wrinkled PDMS film). In addition, three-times and fast-response tunability of the sliding angle by applying mechanical strain on this dual-roughness surface is demonstrated.