Atmospheric pressure plasma jet interacting with a droplet on dielectric surface

The chemical processes at plasma-liquid interface has become a crucial point for plasmas' various applications. In this study, the interaction between atmospheric pressure plasma jet and different-scale droplets were investigated by both experiments and modeling. The interaction transited from 'annular' mode to 'solid' mode when plasma involved with different size of droplets. As the droplet size increased, the high-field region moved from the plasma jet head to the gap between plasma jet head and droplet vertex surface. Additionally, the time averaged surface fluxes of the main active species were analyzed. For the flux of singlet oxygen (1O2), both small and medium-scale droplets reached the maximum value in the central region of the droplets, while for large-scale droplet, the maximum value was observed in the edge region of the droplet. This was due to the fact that, compared to small and medium-scale droplet, the edges of large-scale droplet are closer to the He-Air mixed boundary layer, where more oxygen molecules were provided in the gas environment, leading to enhanced electron collision reactions with oxygen molecules. The cause for these behaviors were also analyzed and discussed. This work shed light on the interaction mechanism for plasma-liquid interactions, which provides significant guidance for plasma medical or water treatment applications.