Comparison of hydrophilization effect by various gas atmospheric plasma

Summary form only given. Atmospheric pressure plasma devices provide some advantages in industrial fields because they don´t require vacuum equipment. Recently, many types of atmospheric pressure plasma sources have been developed, such as capacitive coupled glow discharge, corona source and plasma jet such as plasma burret. In particular, atmospheric plasma jet sources have been attracted attention because of its usefulness for surface treatment or sterilization. However, conventional plasma jet sources have some limitations in the plasma gas spaces and problem of irradiation damage for target surface such as thermal or electric discharge damage. In our research group, damage-free multi-gas atmospheric plasma jet source was developed. The plasma source can generate stable atmospheric plasma jet with helium, argon, oxygen, neon, nitrogen, carbon dioxide, air and their mixed gases. This plasma source is damage-free which means low temperature of the flowing plasma gas and no risk of discharge damage to the target materials. Therefore, it is possible to be applied for not only plastic or silicon wafer but other every material such as paper, textile, metal, bio material and also human skin. The plasma source is very small and light weight. It is 83 mm long and 160 g. We used this plasma source for hydrophilization of polyimide film. Polyimide materials have been widely used as thermal control materials and flexible substrates for light weight, high power solar cells because of their high strength, low density, temperature stability, excellent insulation properties, ultraviolet stability and infrared transparency. Polyimide film was irradiated with 5 L/min of helium, argon, oxygen, nitrogen and air gas plasma. As a result, nitrogen plasma is most effective in hydrophilization, and water contact angle decreased from 70° to 30° on processing speed of 500 mm/sec. This processing speed is 10 times faster than air plasma´s processing speed which is fast pr- viously. In addition, hydrophilization effect of polyimide film sustained a month after. Surface chemical compositions for polyimide surface were characterized by X-ray photoelectron spectroscopy after plasma irradiation. As a result, oxygen-containing chemical bonds were increased by oxygen plasma and nitrogen plasma.