| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 103 === In this study, we developed a round argon-based non-thermal atmospheric pressure plasma jet (APPJ), which was carefully characterized by alcohol thermometer, optical emission spectra (OES), high-voltage probe, and Rogowski type current coil. The temperature of our APPJ is lower than 37°C, which will not induce damage to living tissue. Furthermore, while studies suggest that reactive oxygen species (ROS) play important roles in microorganism sterilization, OES measurements indicate that there are relative high amount of hydroxyl (OH) radicals in our APPJ, while the OH intensity increases with the addition of oxygen. However, OH intensity decreases dramatically after the oxygen percentage becomes higher than 0.04% due to quenching effects. D-value is the time required at a given temperature to kill 90% of the exposed microorganisms. For sterilizing experiment, our argon APPJ has a D-value of 5.5 and 2.7 seconds for E. coli and B. subtilis bacteria within the first 9 seconds of pure argon plasma treatment respectively. For plasma treatment time longer than 9 seconds, the D-value will increase to 16.1 and 7.8 seconds respectively. The sterilizing efficacy of B. subtilis is slightly better than E. coli which is maybe due to the difference of cell wall structure or cell size. For endospores, it takes 49.7 seconds to inactivate 90% of Bacillus subtilis endospore in the first 60 seconds of plasma treatment, while the efficacy will reduce to 111.6 seconds for longer treatment. Addition of oxygen will increase the inactivation area on agar dishes for all 3 microorganisms until the percentage of 0.02. More than 0.02% of oxygen will decrease the sterilization efficacy. At last, observation on scanning electron microscope (SEM) shows morphological rupture on all 3 microorganisms after plasma treatment.
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