Localized electrosynthesis of polypyrrole by application of short voltage pulses.

By the application of short voltage pulses to a tool electrode in close proximity to a substrate electrode, the electro-polymerization of pyrrole in aqueous solution was locally confined with down to micrometer precision. Depending on the pulse parameters polypyrrole towers with up to 100 microm height and about 50 microm diameter were fabricated on the substrate. The spatial confinement of the electro-polymerization reaction is explained by the local charging behavior of the double layer capacitance during voltage pulses of only 100 ns to 10 micros duration. Additionally, the 3D morphology of the polymer patterns is influenced by the diffusion of the educts and intermediate reaction products in the gap between the tool electrode and the substrate. Proper choice of the tool substrate distance and the pulse to pause ratio of the pulse trains allows the deposition of structures whose morphologies vary from fiber-like to cauliflower-like and compact.