Comparison of Antibacterial Effect in at Mosphericpressure Plasmas Excited with Fast-Rising Voltage Pulse

Abstract

Summary form only given. Antibacterial effect was studied in cold plasmas excited by fast-rising voltage pulse. The antibacterial effect was measured on the basis of total mortality and temporal dependence of survived population of micro-organism: spore forming bacteria of Bacillus genera and Aspergillus niger. Control characteristics and antibacterial effect is compared with another type of cold plasma excited by pulse-modulated high-frequency. Notable results in this experiment: 1. Control scheme of plasma homogeneity using fast rising voltage pulse and pulse-modulated high frequency. 2. Antibacterial effect was compared in different experimental conditions using carrier materials, for helium/oxygen mixture and helium/nitrogen mixture. In helium/nitrogen mixture, primary sterilization effect resulted by UV:NO-gamma emitted by NO radical. Antibacterial effect of atmospheric-pressure Townsend-tvpe discharge was evaluated, for Geobacillus stearothermophilus, coated on filter-paper carrier at 6.8x10 CFU. Total sterilization time varied from 30 to 150 sec. around hot-spot, near the discharge region, and 900 sec. around cold-spot. Typical measurement for the shortest D-time constant leveled 10 sec./decade. 3. Antibacterial effect for Bacillus atrophaeus spores at 3.8 x 106 CFU showed total sterilization time, 300 sec. around hot-spot and 900 sec. for cold-spot. Experimental comparison of antibacterial effect is tested using Aspergillus niger spores. Relative strength of the antibacterial effect is discussed for the helium/nitrogen and nitrogen base atmospheric pressure plasma discharge.