The effect of discharge uniformity on the tailing phenomenon of spore inactivation by cold atmospheric plasma

Like other sterilization methods, the tailing phenomenon is ubiquitous in plasma sterilization, typically manifested as a survival curve that exhibits a rapid decline followed by a prolonged tailing period. While factors such as bacterial resistance and plasma power have been extensively studied in the sterilization process, the critical role of discharge uniformity remains insufficiently explored. One key challenge is the lack of quantitative methodologies for assessing discharge uniformity. Therefore, this study proposes a lattice model for quantitative evaluation parameters for plasma distribution uniformity (Up) and spore distribution uniformity (Us). Based on this framework, the sterilization mechanisms under varying discharge uniformity were investigated, with a particular focus on their influence on the tailing process. A comprehensive investigation was conducted, integrating experimental data, population-level microscopy, and modeling. The results show that bacterial clusters, where inner bacteria are shielded by outer layers, generate resistance dispersion, contributing to the tailing phenomenon. Under equivalent total plasma energy, increased discharge uniformity reduces streamer filaments and enhances the interaction probability between plasma and bacterial clusters. This significantly mitigates the tailing phenomenon and shortens the sterilization time. These findings provide valuable insights into the mechanisms of plasma sterilization and have implications for the design of more efficient plasma-based disinfection systems.