Atmospheric-Pressure Plasma Reduction of Metal Cation-Containing Polymer Films to Produce Electrically Conductive Nanocomposites by an Electrodiffusion Mechanism

We describe an atmospheric-pressure plasma process for the reduction of metal cation-containing polymer films to form electrically conductive patterns. Thin films of poly(acrylic) acid (PAA) containing silver ions (Ag⁺) were prepared by mixing the polymer with silver nitrate (AgNO₃) in solution to produce a cross-linked precipitate, homogenizing, and depositing onto a substrate by doctor’s blade. Exposing the Ag–PAA films to a scanning microplasma resulted in reduction of the bulk dispersed Ag⁺ in a desired pattern at the film surface. The processed films were characterized by scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and current–voltage measurements. The resistances of the patterned features were found to depend on the thickness of the films, the microplasma scan rate, residual solvent in the film, and electric field created between the microplasma and the substrate. Together these results show that the formation of conductive features occurs via an electrodiffusion process where Ag⁺ diffuses from the film bulk to the surface to be reduced by the microplasma.