Research On Device For Sterilization By Self-discharge Plasma

Using atmospheric pressure cold plasma to inactivate pathogenic bacteria has become one of great importance for preventing and controlling infections and ensuring medical quality.This paper proposes a new combination of ion wind and self-excited plasma jet device for the current cold plasma device which requires a huge external carrier gas system and not conducive to carry.The practical work is as follows:Firstly,this paper has designed a cascade single needle-to-grid and multiple needle-to-grid sterilization device based on the experiment of the needle-to-grid ion wind velocity.Through the wind speed measurement experiment with two devices,it showed that the voltage value increases with the increase of the wind speed with other conditions unchanged.The wind speed also increases with the increase of the number of stages,but it will gradually become stable.When the number of stages is ten,the wind speed can reaches 4.57 m/s.By contrast to the wind speed by positive and negative corona discharges,negative ion wind speed is greater.Due to several needles and grid discharge in each stage of the multiple needle-to-grid device simultaneously,which interfere the experiment results.The sterilization device and experimental power source is ten single needle-to-grid device and negative high-voltage DC power source respectively.It was verified that cascaded single-needle-to-grid ion wind can kill bacteria,and the sterilization effect grows gradually with sterilization time.Secondly,in order to improve the miniaturization of the plasma sterilization system,this paper has designed and developed a MEMS need-to-column array chip device of the Lithographie,Galvanoformung and Abformung(LIGA)technology fundamentals by the stable ion wind experiment with the needle-column discharge.In the case of stable discharge,we performed a sterilization experiment.It showed that under the conditions of changing the sterilization time,the sterilization rate also increased with the increase of the sterilization time.At the same time,it was found that the sterilization distance has an effect on the sterilization effect.If it is too long,the sterilization efficiency will be reduced or even no effect.Thirdly,using direct-current(DC)discharge designed a portable self-excited needle-rectangular-loop sterilizer at atmospheric pressure,which can generate stable positive and negative air plasma jets.At the same time,the negative plasma jet killed Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)at the sterilization time of 60 s and 120 s respectively,and the positive plasma jet killed E.coli and S.aureus at the sterilization time of 120 s and 150 s respectively.It can be concluded that the positive and negative plasma jet have great differences between Gram-negative bacteria and Gram-positive bacteria in the sterilization effect,and the sterilization rate of the positive plasma jet is better than the negative plasma jet.Thus,the sterilization efficiency of the E.coli exceeds that of the S.aureus.Finally,we designed a horizontal and vertical integrated system combined a ten single needle-to-grid ion wind devices with a needle-rectangular-loop plasma jet device.The discharge experiments showed that the sterilization effect of the vertical system was better.The plasma jet was more longer and more stable using a vertical integrated.It showed that the ion wind device could replace the carrier gas and realize a self-intake plasma jet system.The length of the plasma jet and the sterilization effect could be changed by the number of stages of the ion wind device and the applied voltage of the ion wind device.