Surface modification of halogenated polymers. 9. Etching of polytetrafluoroethylene with the scanning electrochemical microscope

A polytetrafluoroethylene (PTFE) surface can be patterned along carbonized stripes by a scanning tip maintained at a constant tip/surface distance and biased at the reduction potential of a redox mediator (E0 < −2.10 V/SCE). The dimensions of the etched stripes are correlated to the scan rate, the charge passed through the circuit, and the electrode radius. The expansion of the PTFE carbonization is governed by an in-depth diffusive process. It proceeds along a hemi-cylinder of hemi-elliptic section, the lateral expansion being much easier than the in-depth one. The contrast between the hydrophilic etched stripes and the hydrophobic virgin surface should find applications for microfabrication on perfluorinated surfaces.