Parallel Plate Cold Atmospheric Pressure Plasma Source for Destroying Bacteria and Biofilms

Abstract

Cold atmospheric pressure (CAP) plasma has been shown to kill bacteria and destroy biofilms through reactive etch and sputter activity. CAP plasma could be used to debride wounds or to remove bacteria from surfaces, including in the food processing industry where microbial contaminants are a source of food-borne illness. We have developed a parallel plate, capacitive discharge device operating at 20 kHz and 3–5 kV. The device is fabricated from a Low Temperature Co-Fired Ceramic (LTCC) and can be varied in both discharge width (0.2-5 cm) and gap (0.1-3 mm). The two silver metal electrodes for the discharge are completely covered with a 35 μm layer of LTCC. Multiple CAP sources can be stacked together to produce arrays of sources. Mass flow controllers allow argon and oxygen to flow between the plates during the discharge. The CAP plasma has been shown to completely remove 4-day E. coli 0157:H7 biofilms from glass coverslips and kill Staph. aureus cells in 2-day biofilms. Channels etched in the biofilm have been measured with a stylus profilometer and indicate removal rates of > 50 nm/s. CAP plasma also caused a 3-log reduction in viable colony forming units (CFU) with less than 150 s exposure. The source is currently being optimized in terms of operating power, gas flows, and geometry to improve the biofilm removal rate. These results will be presented.