The Numerical Simulation Of Reactive Species Transfer In The Interaction Between Gas Plasmas And Aqueous Solutions

In the past few years,cold atmospheric-pressure plasmas(CAPs),due to their great reactivity and low temperature property as well as no need for vacuum system,have received much interest in a large variety of plasma applications,such as plasma sterilization,environment protection,polymeric modification,and plasma medicine.Especially,more and more experimental evidence suggests that CAPs are of enormous potential in biomedical engineering including disinfection,surgical procedures,would healing,and even cancer treatment.In these applications,the plasmas are used to irradiate the biological tissue,obtaining the expected biomedical effects.The biological tissues treated in plasma medicine are coated by a water layer,usually being hundreds of micrometers thick.On the other hand,it has been found that when the biological tissue treated in an aqueous enviroument,the dominant reactive species may be very different from the plasma itself.Hence,the mass transfer of reactive species in the penetration process of plasmas into this layer of liquid becomes primary and crucial topic in the study of plasma medicine.Experimentally,direct concentration measurements of the species in liquid region have been reported for plasma-activated water.In spite of this,the distributions of the species in the liquid region are not provided experimentally because of the limited measuring techniques.Therefore,the numerical simulation is a practicable solution to the evaluation of the species distributions in the mass transfer of reactive species in the liquid region.In this work,the mass transfer of the reactive species from the plasmas in the liquid layer has been investigated by means of the numerical simulation based on the one-dimensional drift-diffusion model.The highlight of this work is to consider the dissociative electron attachment(DEA)to water molecule by increasing electron energy in the plasmas and to investigate the depth distributions of five main reactive species,OH,O3,HO2,O2-,and H2O2.The present work shows that the consideration of the DEA to water molecule is of great influence on the depth distributions of HO2,O3,and OH.With the increase of electron energy,HO2 becomes short-living species,quenching after the penetration depth of a few micrometers,but the penetration depths of O3 and OH increase evidently,up to a few tens micrometers.In addition,the contribution of each dominative reaction to production or loss of OH has also been calculated and analyzed under the different electron energies,providing a good knowledge for the mechanisms of OH production as well as its penetration in the liquid layer.The present work is a first effort toward the goal of increasing the different types of the reactive species that may interact with cellular components after the mass transfer of the plasmas in the liquid layer by changing the reaction pathways of the liquid region,which is of significance for the application of CAPs in biomedical engineering.