Formation of self-organized gradient stripes on precast poly(methyl methacrylate) films

A "wire-on-film" template has been developed to construct surface gradient patterns on precast poly(methyl methacrylate) films. Solvent evaporation around a Cu wire leads to the formation of self-organized gradient stripes, with the longitudinal direction of the stripes being parallel to the axis of the Cu wire. Both the spatial wavelength and the amplitude of the stripes near the Cu wire decrease with a decrease of the distance to the center of the Cu wire. The amplitude of the stripes varies linearly with the spatial wavelength for the experimental conditions used, which is a function of the diameter of the Cu wires and the film thickness. Using two parallel copper wires, we demonstrate the possibility of controlling the characteristics of the gradient stripes. A featureless zone is formed between the copper wires, the size of which is dependent on the distance between two wires and the diameter of the copper wires. The results of this study provide a simple method to fabricate gradient gratings on polymer films in an economical and efficient way.