Open-Air Bacterial Inactivation using a RF Powered Hollow-Slot Plasma Device

Summary form only given. The use of atmospheric pressure plasma sources for biomedical applications is primarily because of the capability to employ devices for bacterial inactivation at close to room temperature without the use of dangerous chemicals. This improves both the ease of bacterial inactivation and is important for treatment of heat-sensitive materials. Plasma based inactivation is much faster and cleaner compared to some of the conventional technologies like autoclaving and ethylene oxide treatment that are normally used for sterilization. Our research is focused on the impact on bacteria, of a wide area afterglow plume emitted from a hollow-slot electrode configuration that operates in open air and is RF powered. We employ a grounded hollow slot as the interface to the work piece so that the device may be hand held. In the work reported herein the device dimensions are; 7.62 cm long, 0.02 cm wide and 0.2 cm deep, but note 30 cm long versions are operable as well. Recessed behind the grounded slot is a powered electrode employing 60 MHz electrical drive. A mixture of argon and oxygen gases flows from the powered electrode through the grounded slots creating a plasma afterglow plume, which extends 1-8 mm past the open slot and is 7 cm long. The afterglow plume is line shaped and is visible in open-air operation. Use of rare gases is considered a disadvantage for some portable applications. We also report operation in pure air but indicate the limitations we uncovered. Using Escherichia coli as the test bacteria, we have witnessed promising results with a colony forming unit (CFU) reduction of seven logs, which meets commercial sterilization requirements of six logs removal. Moreover, this was accomplished with only 2 seconds total exposure time. The experiments to date demonstrate the potential of the open-air hollow-slot applicator to inactivate bacterial growth in a wide area environment with a device that could be hand held