Diagnostics of cold atmospheric pressure plasma jet and its antimicrobial properties

Cold atmospheric pressure plasma jet (CAPPJ) has many applications in biomedicine. Using argon as a carrier gas, the gas temperature, remains at room temperature even after hours of operations. The plasma jet can be touched by hands and directed manually by a user to bring in contact with heat-sensitive objects and materials including skin without causing any heating or painful sensation. CAPPJ was generated by a high voltage power supply (0-20 kV) at an operating frequency of 25 kHz. The discharge was characterized by an optical method. In order to characterize the plasma jet, its electron temperature and electron density were determined by optical emissions spectroscopy. This paper reported the antimicrobial property of cold atmospheric pressure plasma jet. The result indicated that CAPPJ treatment was capable of killing the microbial population in its exposed area. Plasma jet was used to treat selected strains of pathogenic bacteria for varying voltage (4 kV and 5 kV) and varying time duration (10 sec, 15 sec, and 20 sec). Among the selected strains, E. coli showed the smallest zone of inhibition (ZOI), K. pneumonia showed the largest zone of inhibition. The reactive compounds contain in the cold plasma jet: high-energy electrons, ionized atoms, and molecules, and UV photons were the key factors that caused an effective reduction in the number of micro-organisms.