The interaction of an atmospheric pressure plasma jet with liquid water: Dimple dynamics and its impact on crystal violet decomposition

The interaction of atmospheric pressure plasmas with a liquid can result in the deformation of the gas-liquid interface. In this paper, we report on the gas-liquid interfacial dynamics during the impingement of an argon radio frequency driven atmospheric pressure plasma jet (APPJ). The dynamics of the dimples generated during the impingement of the APPJ on the liquid depends on the plasma power, gas flow rate, size of the liquid container and the distance of the APPJ nozzle to the liquid surface. When the plasma is in contact with the liquid, the dimple oscillation frequency correlates with the dynamics of the plasma filament. At larger jet-liquid distances, the APPJ behaves similar to a gas jet although in most cases with an enhanced deformation of the liquid interface or change in dimple dynamics. The observed dimple oscillations can significantly enhance the decomposition efficiency of crystal violet by enhancing liquid phase convection. The conditions studied in this paper are similar to typical conditions for in vitro plasma-bio-interaction studies and the plasma-induced interfacial liquid dynamics, which is often not considered in many studies, might enhance plasma-induced liquid phase chemistry and reactivity.