Solvent vapor-assisted imprinting of polymer films coated on curved surfaces with flexible PVA stamps

We report a simple yet robust and reproducible technique to create surface patterns with submicrometer scale resolution on polymer films coated on nonplanar and curved surfaces at room temperature, without applying any external pressure. The imprinting is achieved by using a flexible, patterned polyvinyl alcohol (PVA) stamp in a controlled solvent vapor atmosphere, where the patterned foil comes in adhesive contact with a swollen and softened polymer film. The stamp bends along the contours of the curved surface to make a complete contact with a soft and swollen viscoelastic polymer film to make an imprint. The soft surface of the film then deforms on the length scale of each structure on the stamp to make a conformal contact, forming a negative replica of the stamp pattern on the film surface. The flexible PVA stamp is later dissolved in water after the patterning process is complete. It is shown that the technique is portable across a variety of polymer coatings, substrates, and geometries. Further, we also show that the same technique can be employed to create complex 2-D microstructures on nonplanar surfaces by multiple imprintings