Development of sterilization device using air nonthermal plasma jet induced by atmospheric pressure corona discharge

An innovative sterilization system that uses an air plasma jet induced by an atmospheric pressure corona discharge is developed. Because the sterilization is performed by the plasma reactions of air, the system does not require any preparation of source gas cylinder. To obtain a fundamental understanding of the system, the gas byproducts and the temperature of the plasma jet are investigated. The gas temperature is below the temperature required to kill bacteria and yeast (Escherichia coli and Saccharomyces cerevisiae). Sterilizations by applying the plasma jet for 0–5 s to several pieces of bacteria test paper on which either bacteria or yeast exists are performed. After application of the nonthermal plasma jet, the bacteria or yeast are cultivated in an incubator and then the numbers of colonies on the test piece are counted. From this test, it is found that an exposure time of 1 s suffices to reduce both populations of bacteria and yeast by more than 88%. Complete deactivations of both bacteria and yeast are performed by applying the plasma jet for 5 s.