Phase‐Separation‐Induced Micropatterned Polymer Surfaces and Their Applications

We report a route to fabricate micropatterned polymer films with micro‐ or nanometer‐scale surface concavities by spreading polymer solutions on a non‐solvent surface. The route is simple, versatile, highly efficient, low‐cost, and easily accessible. The concavity density of the patterned films is tuned from 10⁶ to 10⁹ features cm^–2, and the concavity size is controlled in the range from several micrometers to less than 100 nm, by changing the film‐forming parameters including the polymer concentration, the temperature of the non‐solvent and the interactions between polymer, solvent, and non‐solvent. We further demonstrate that these concavity‐patterned films have significantly enhanced hydrophobicity, owing to the existence of the surface concavities, and their hydrophobicity could be controlled by the concavity density. These films have been used as templates to successfully fabricate convex‐patterned polymer films, inorganic TiO₂ microparticles, and NaCl nanocrystals. Their other potential applications are also discussed.