Kinetic model of activation of water layers by humidified air DBD plasma

Abstract Atmospheric pressure air plasmas have shown significant potential in surface bacterial disinfection and inactivation. During plasma treatment, the surface of the treated sample is typically covered by a thin water layer, which acts as a trap that captures gaseous reactive oxygen and nitrogen species (RONS). This trapping mechanism activates the water layer and enhances its biocidal effectiveness. In this paper, a comprehensive kinetic model is established to investigate the role of surface water layers in biological sterilization by exploring the spatial and temporal dynamics of RONS in both gas and liquid phases. The model is experimentally validated by comparing the measured concentrations of key reactive species, specifically O 3 in the gas phase and H 2 O 2aq , NO 3aq − , and NO 2aq − in the liquid phase, while the biological activity of the plasma-activated water layer is evaluated by measuring the survival rate of E. coli . This study investigates the physicochemical processes involved in the activation of water layers by atmospheric pressure plasmas, with a particular emphasis on the mechanisms of reactive species generation and loss in the discharge region, afterglow region, and water layer region. It also examines how variables such as discharge power, gas flow velocity, air humidity, and water layer thickness influence the generation and distribution of RONS. The findings of this study contribute to a deeper understanding of plasma-based sterilization and disinfection systems.