The influence of gas humidity on the discharge properties of a microwave atmospheric-pressure coaxial plasma jet

Jie Yu,Li Wu,Junwu Tao,Xiao Wu,Kama Huang,Wencong Zhang

doi:10.1063/5.0033059

Abstract

This paper investigated the influence of gas humidity (1%, 3%, 8%, 10%, and 12%) on the characteristics of a microwave-induced atmospheric plasma jet. The plasma discharge was generated by a microwave solid-state source with a H2O–Ar mixture gas flow of 8.1 L/min. The variation in energy efficiency, O and OH concentrations, rotational temperature of heavy species, shapes of plasma plumes with different humidities, and microwave input powers were recorded and analyzed. The results showed that the concentrations of O and OH increase monotonously with gas humidity at higher input powers while they fluctuate with gas humidity at lower input powers. With an increase in the H2O/Ar ratio from 1% to 12%, the energy efficiency of the plasma generator decreases, and the plasma plumes become shorter and thinner. The rotational temperature of plasma at the nozzle also showed positive correlation with increasing humidity. Adding more input power would make all the values of these parameters increase. This paper is supposed to be helpful for the research of the interaction mechanism of mix gas plasma and microwave power and for improving the effect of plasma treating biomedical materials.

Highlights

Low-temperature atmospheric-pressure plasma (APP) has been widely used in various biomedical applications,1–3 for instance, in killing cancer cells,4–6 sterilization,7–11 inducing cell apoptosis,12,13 whitening tooth,14 cell adhesion,15,16 regenerating skin,17,18 and so on
This paper investigated the influence of gas humidity (1%, 3%, 8%, 10%, and 12%) on the characteristics of a microwave-induced atmospheric plasma jet
Most investigations concerning low-temperature APP have upheld the fact that chemically active species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), containing oxygen atoms (O), oxygen negative ions (O2−), ozone (O3), hydroxyl radicals (OH), nitric oxide radicals (NO), and hydrogen peroxide (H2O2), play an essential role in biomedical areas as well as other relevant research domains

Summary

Introduction

Low-temperature atmospheric-pressure plasma (APP) has been widely used in various biomedical applications, for instance, in killing cancer cells, sterilization, inducing cell apoptosis, whitening tooth, cell adhesion, regenerating skin, and so on. Most investigations concerning low-temperature APP have upheld the fact that chemically active species such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), containing oxygen atoms (O), oxygen negative ions (O2−), ozone (O3), hydroxyl radicals (OH), nitric oxide radicals (NO), and hydrogen peroxide (H2O2), play an essential role in biomedical areas as well as other relevant research domains.. Reports show that a slight change in the composition of working gas may lead to significant variation in plasma properties, especially active species and their doses, which will affect the plasma treating results. It is necessary to investigate how the gas composition influences the plasma properties, especially the active species. The influence of argon humidity variation on the plasma properties especially on the doses of O and OH is studied with emission spectra based on a self-designed microwave-induced coaxial plasma generator. The change law is studied and discussed by adjusting the gas humidity and microwave input power

Methods

Results

Conclusion