Dielectric barrier discharge generated from the liquid electrolyte

Summary form only given. The water plasmas generated by atmospheric discharges have already demonstrated their potencial also for surface modification of polymer materials and are emerging as a very flexible concept to generate selective functionalized polymer surface. We have developed a novel type of surface dielectric barrier discharge generating thin layers of visually diffuse plasmas along the treated polzmer polymer using water-based electrolyte as a electrodes. This technique has been designed particularly to achieve uniform treatment of outer or inner suface of polymeric tubes and other hollow bodies (e.g. tubes, containers, flasks, catethers). Especially the treatment of inner surface of tubes is a serious challenge for atmospheric pressure plasma processing. In our work we focused on functionaliyation of polzmeric surface, grafting with biocompatible materials and increasing novel properties. The discharge was energized by a sinusoidal alternating current and high voltage power supply with 15-20 kV amplitude and 25-30 kHz frequency. In our experiments PTFE tube (outer diameter - 8mm) was inserted vertically into water-based electrolyte (5% solution of oxalic acid) and filled by the same solution. Both electrically insulated volumes of solution serve as a liquid electrodes. The surface dielectric barrier discharge is always generated from the contact line of the lower liquid surface with dielectric wall of PTFE tube, so in principle the simple control the level of inner or outer surface liquid can change the location of inner and/or outer plasma treatment. During the plasma treatment the tube was moved vertically up. The diffuse plasma layer was generated in ambient air with an unspecified content of water and electrolyte molecules evaporated by the discharge. After treatment the strong and stable hzdrophylic treatment was observed. This was exemplified by the permanent surface oxidation and replacement of a high fraction of the surface determined by XPS.