Fig. 1.

Spontaneous surface patterning via reversible creasing instability. (A) The procedure of patterning consists of three steps: (i) coating substrate with a polyurethane elastomer film; (ii) unidirectional swelling of the geometrically constrained polyurethane film in a solution containing poly(ethyl methacrylate)/fluorodecyl POSS in Asahiklin solvent, leading to creases formed on the surface; and (iii) withdrawing the sample from the coating solution resulting in a PEMA/POSS coating to the exposed regions, and evaporation of Asahiklin solvent causing the polyurethane film to deswell, which leads to unfolding of the creases and exposure of the uncoated self-contact regions. (B) Optical micrographs showing creases observed on the polyurethane film surface (Upper) and a patterned surface via reversible creasing (Lower). (C) A fluorine element intensity line profile by EDS showing the deposition of hydrophobic fluorodecyl POSS molecules on the exposed regions. (Scale bar, 100 μm.)