We performed open-air plasma treatment of polytetrafluoroethylene (PTFE) at atmospheric pressure to increase the adhesion strength between PTFE and an Ag metal film formed from Ag ink. Coloration of the PTFE surface occurred during 600 s treatment with Ar plasma. The Ag/PTFE adhesion strength was 0.06 N/mm. To resolve the problem of coloration and to improve the adhesion strength, O2 or H2 gas was added. During treatment with Ar+O2 plasma with O2 content of 0.33% for 600 s, no coloration occurred but the adhesion strength decreased to zero. During treatment with Ar+H2 plasma for 600 s, coloration did not occur. Moreover, the adhesion strength increased to 0.25-0.55 N/mm. These results showed that H2 addition was effective for preventing coloration and improving adhesion strength during long-period plasma treatment. Furthermore, the uniformity of surface treatment with Ar+H2 plasma was higher than that for Ar plasma.
Hydrogen･oxygen nanobubbles were generated in 0.1-1.0 m mol/L Na2SO4 solutions using anomalous high-frequency AC electrolysis （-pole and ±poles, 30 kHz）. The bubble size distribution was 20-600 nm. The maximum bubble number density was about 4 million per milliliter at the size distribution position of 100 nm. The bubble number density of the solution boiled for 2 min did not decrease, but instead increased slightly. After 26 days, the nanobubbles were found to exist almost stably.