Versatile approach for the fabrication of functional wrinkled polymer surfaces

A simple and versatile approach to obtaining patterned surfaces via wrinkle formation with variable dimensions and functionality is described. The method consists of the simultaneous heating and irradiation with UV light of a photosensitive monomer solution confined between two substrates with variable spacer thicknesses. Under these conditions, the system is photo-cross-linked, producing a rapid volume contraction while capillary forces attempt to maintain the contact between the monomer mixture and the cover. As a result of these two interacting forces, surface wrinkles were formed. Several parameters play a key role in the formation and final characteristics (amplitude and period) of the wrinkles generated, including the formulation of the photosensitive solution (e.g., the composition of the monomer mixture) and preparation conditions (e.g., temperature employed, irradiation time, and film thickness). Finally, in addition, the possibility of modifying the surface chemical composition of these wrinkled surfaces was investigated. For this purpose, either hydrophilic or hydrophobic comonomers were included in the photosensitive mixture. The resulting surface chemical composition could be finely tuned as was demonstrated by significant variations in the wettability of the structured surfaces, between 56° and 104°, when hydrophilic and hydrophobic monomers were incorporated, respectively.