Change in surface tension of water in atmospheric pressure plasma-liquid interaction

We've demonstrated that measuring surface tension is a good way to look at the plasma–liquid contact in real-time. A method based on the dispersion relation of an acoustic capillary wave created on the water surface was used to detect surface tension. The surface tension steadily rose over time when the water surface was bombarded with the outside region of the spatial afterglow of an atmospheric-pressure plasma. During plasma irradiation, the Marangoni effect was detected, which was related to a localized rise in surface tension. After the discharge was completed, the surface tension was reduced. The fluctuation of the OH radical density in the gas phase was shown to be related to the temporary drop in surface tension. In the solution containing a trapping agent for liquid-phase OH radicals, there was no increase in surface tension. The results of these experiments imply that OH radicals enhance surface tension. The behavior of the surface tension, on the other hand, cannot be fully explained by considering solely the activity of OH radicals. We have also examined the interaction between plasma and liquids with low surface tension.