Microbial Inactivation by Electric Discharge with Metallic Grid

Abstract

The rapidly developing eld of plasma decontamination and medical applications was previously reviewed many times, e.g. in [1 5]; a paragraph devoted to action to bacteria is involved also in [6]; recently, a book devoted to this topic was also edited [7]. The non-thermal plasma for this purpose was mostly produced in air by dielectric barrier discharges, gliding arc, plasma torches and various corona discharges; we compared microbicidal properties of various corona discharges in [8]. In other papers [9, 10] we reported a new type of jet-like point-to-point DC electric discharge produced in atmospheric air and named cometary. We also described here the ability of cold plasma produced by this discharge to inhibit the growth of Escherichia coli and Staphylococcus epidermidis bacteria on agar plates and on human skin. The cometary discharge is similar to this one produced by devices called plasma jet torch, plasma pencil, or plasma needle, which generate the low-temperature plasma by RF in a stream of carrier gas [11, 12]. In the study [13], the mechanism of decontamination was studied using the grounded mesh electrode inserted between the positive electric discharge and the target sample, here a contaminated agar plate. This electrode (metallic grid) shielded the electric eld and trapped the charged particles, but allowed the neutral particles and UV light to reach the agar surface. The experimental arrangement used in this study is similar, except the use of cometary discharge and the inserting of electrically insulated metallic grid.