Characteristics of cold atmospheric pressure plasma jet and its antimicrobial activity

Cold atmospheric pressure plasma jet (CAPPJ) has been approved by several investigators as anti-microbial agent [1]. In this experiment, CAPPJ in air is generated by applying AC voltage 7-14 kV (peak-to-peak), with frequency of 21-29 kHz to Al₂O₃ tube. The tube has 150 mm length with a 4 and 6 mm inner and outer diameter, respectively. Argon flow rates ranged from 0.1 to 10 SLM were blown through the tube to form the plasma jet. The addition of oxygen to argon as operating gases enhances the generation of O and OH radicals. The electric and spectroscopic characteristics of the generated plasma jet were investigated. The generated plasma jet length and mode of operation varied as a function of oxygen flow rate percentage, applied voltage and frequency. The plasma jet length increases with argon flow rate to reach its maximum at 5 SLM then ceases to reach saturation at 8 SLM. The energies consumed by the discharge were estimated using the charge-voltage curve (Lissajous figure). The consumed energy increased with increasing the input power. Regarding the decontamination, the data indicate an optimum condition of E. coli sterilization at 0.02% of oxygen.