a method of forming a relief pattern on the surface of a substrate comprises the steps of providing a substrate , coating a thin layer of polymeric material onto the substrate , drying the polymeric material to leave residual lateral stress within the material , bringing a patterned stamp into contact with the polymeric material and applying pressure to the stamp such that the polymeric material ruptures patternwise and dewets at the surface of the substrate to form openings in the polymeric layer according to the pattern on the stamp .