Control of droplet size and spacing in micrometer-sized polymeric dewetting patterns

When a polymer solution is cast on a flat substrate and the solvent is allowed to evaporate, dewetting might take place. Instead of a continuous film, the polymer forms micrometer-sized droplets. By controlling the solvent casting process with the help of a roller apparatus, the size and spacing of the polymer droplets can be adjusted. We investigated the effect of polymer concentration and roller speed on the pattern dimensions and found that higher concentrations lead to larger polymer droplets (from 1 to 11 microm), whereas faster roller speeds lead to a wider interdroplet spacing (from 4 to 130 microm).