Micro-nano 3D printing of electronically conductive polymers as a new process for achieving higher electronic conductivities

We have already reported multi-photon excitation of tris(2,2′-bipyridyl)ruthenium complex [Ru(bpy) ₃ ²⁺ ] by femtosecond pulse laser with near infrared wavelength as the light sources, the multi-photon sensitized polymerization of pyrrole and the 3D printing (photo-fabrication) system of polypyrrole (PPy) by 3D scanning of the laser focal point. In the present study, the 3D printing of PPy into a Nafion sheet was carried out to evaluate the electronic conductivity of the product micro-structures formed by multi-photon sensitized polymerization. When the PPy straight line structure was drawn in the direction of the optical axis (vertical), relatively higher conductivity values (Max 410 Scm⁻¹) were obtained in the fully-doped state. The values of over 10² Scm⁻¹ indicated the Drude model of electrical conduction, therefore, the micro-structures would be applied to a metamaterial. On the other hand, 1 or 2 orders of magnitude lower conductivity values were obtained from the crooked line structures drawn in the vertical and horizontal directions. This difference in the conductivity would be affected by the distorted cross section of the PPy deposition and the electrically overlapping of each deposition particle.