| In recent years,the research of atmospheric low temperature plasma has been a hotspot in plasma science and technology application,and biological sterilization is one of its important applications.With the increasing drug resistance of pathogenic bacteria,it's urgent to study the equipment and sterilization mechanism of sterilization plasma.The purpose of this paper is to study the sterilization device and sterilization mechanism of atmospheric pressure dielectric barrier discharge.Firstly,the sterilization devices and the mechanism were studied.Secondly,the experimental parameters of DBD device were changed,and its effect on sterilization was analyzed.Then,the better device and parameters were given.Finally,the sterilization factors and sterilization mechanism of DBD device were explored by changing the reaction gases flow rate and type.The details are as follows:Based on needle-medium-ring structure,a small DBD test tube treatment device was developed and applied to liquid sterilization.The main way to destroy bacteria was that the protein in bacteria was destroyed.A flat-panel DBD device was designed to study the effect of experimental parameters on sterilization efficacy by changing the types of power supply,voltage,dielectric material and gap size.The result shows that:under the same power condition,the sterilization efficiency of pulsed power supply is higher than that of AC power supply because of its higher electronic energy,better particle concentration and activity;the sterilization efficiency of high voltage and small gap is higher because of the higher field strength;glass and porous ceramics have better germicidal efficacy than ordinary ceramics.The optimal experimental device is put forward.The experimental conditions of inactivating six orders of Bacillus subtilis in 90s are firstly proposed:flat-panel DBD,pulse rising edge is 140ns and peak value of main discharge is 700,dielectric material used is porous ceramics or glass and the gap size is 2mm.Flat-panel DBD was applied to liquid sterilization.The mechanism of sterilization was analyzed by SEM and FTIR.Plasma destroyed the cell structure and internal proteins of Escherichia coli.Reaction gases on sterilization mechanism of DBD were studied.Sterilization efficacy disappeared when the air velocity was increased to 0.4slm,because the breakdown voltage reduced and reactive particles were blow away.By changing the gas type to helium,the sterilization efficacy becomes worse,because the types and quantities of reactive particles produced by'different gas types are different.Comparing the 1slm flow rate air with the static helium,it can be concluded that the main reason for reduced sterilization efficacy is that reactive particles are blown away by flow air.It was found that the sterilization efficacy was improved by increasing the content of water vapor in the gas.And it was analyzed that the reason was not the increasing OH concentration but other concentration of reactive particles such as ROS and RNS.Finally,the sterilization mechanism of flat-panel DBD is proposed:the sterilization factor is not UV and temperature.Charged particles and reactive chemical particles are the main sterilization factors,and their effects are parallel.Charged particles destroy cell membranes and other cellular structures mainly by electrostatic destroying,which results in the outflow of internal substances.Reactive chemical particles can inactivate cells by destroying proteins,lipids,DNA and RNA in cell structure.The paper presents an efficient sterilizing device and analyses its sterilizing mechanism,which provides a reference for developing more DBD sterilizing devices with safety and efficiency.Also,it makes DBD more widely used in the field of sterilization,and provides new ideas for dealing with various strong pathogens.This will not only promote the development of DBD,but also show great value on plasma science. |
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