Effect of gas composition on surface sterilization by using LF-microwave hybrid plasma source

Abstract

A new type of atmospheric-pressure non-thermal plasma source was developed by a combining a low-frequency (LF) plasma jet with microwave plasma as a hybrid plasma. The LF-microwave hybrid plasma has a large amount of reactive species compared to conventional LF plasma jet owing to higher-energy electrons, which are accelerated by the oscillating electric fields of the microwave. Moreover, it can be sustained stably at a higher composition rate of the process gas in the discharge gas. The objective of this study is to investigate the effect of the admixture gas composition on surface sterilization by using our self-designed LF-microwave hybrid plasma source. The influence of the discharge gas composition ratio between oxygen and argon on the production of the reactive species and sterilization effect was investigated. The analysis of the optical emission spectra and the reaction of the chemical indicators reveal that reactive oxygen increases with the increasing ratio of oxygen in the oxygen-argon admixture discharge gas up to an oxygen ratio of 10% and then it saturates. In contrast, the results of the sterilization test using biological indicators indicate that a higher sterilization effect was obtained for a lower ratio of oxygen in the admixture discharge gas. It is considered that reactive species, except reactive oxygen, are related to surface sterilization using atmospheric-pressure non-thermal plasma.

Effect of LF-microwave hybrid plasma treatment on radish seed germination and sprout growth

“…The LF-microwave hybrid plasma source is composed of a rectangular waveguide (WRJ-2), which contains a cylindrical slotted antenna surrounding a discharge quartz tube, and a cylindrical copper electrode, which is installed in the discharge quartz tube. [27][28][29] Two slits are arranged on the cylindrical slotted antenna. The frequency of the microwave was 2.45 GHz and the power could be increased up to 2 kW.…”

“…A short plunger was installed for impedance matching between the plasma and the microwave circuit, and the forward, reflected powers were measured by using a directional coupler with power meters. [27][28][29] The flow rate of each gas was adjusted by each gas-flow controller. The LF plasma jet was generated at the beginning of the operation by applying an LF high voltage to a cylindrical copper electrode in the discharge quartz tube.…”

“…[23][24][25][26] In our previous study, a new type of atmospheric pressure non-thermal plasma source, combining a low-frequency (LF) plasma jet with a microwave plasma source was developed as a hybrid plasma. [27][28][29] The LF-microwave hybrid plasma was initiated by the LF plasma and expanded by the dissipation of microwave power. The LFmicrowave hybrid plasma has a large number of reactive species compared to conventional LF plasma jet owing to higher-energy electrons, which are accelerated by the oscillating electric fields of the microwave.…”

“…The results obtained by applying LF-microwave hybrid plasma on the surface sterilization of medical equipment demonstrated that the reactive species generated in the hybrid plasma are considered to play an important role in bacteria sterilization. [27][28][29] Therefore, a large number of reactive species generated in LF-microwave hybrid plasma, such as reactive oxygen species (ROS) and reactive nitrogen species (RNS), were considered to reduce the pathogenic contamination of seed surface and stimulate plant growth.…”

Metabolomics of Pseudomonas aeruginosa Treated by Atmospheric-Pressure Cold Plasma

“…They found that the plasma had a significant bactericidal effect [21]. Shintani et al found that the primary cause of nitrogen plasma sterilization was the active particle ONOO − [22], and Tonmitr et al investigated the effect of different working gases on bactericidal efficacy [23]. Nguyen et al reported a plasma-based nanomaterial that promotes apoptosis of cancer cells [24].…”