Microsecond-Pulsed Dielectric Barrier Discharge Plasma-Treated Mist for Inactivation of Escherichia coli <italic>In Vitro</italic>

Abstract

In this paper, we demonstrate a plasma misting system capable of inactivating Escherichia coli O157:H7 (E.coli) in a 4 ft <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (approximately 100 L) volume with potential for future use in decontaminating fresh produce. Water droplets, with an average diameter of 5 μm, are generated via ultrasonic nebulizers and carried by compressed air. These micrometer-sized droplets flowthrough a set of three cylindrical, microsecond-pulsed dielectric barrier discharges (DBDs). We observe the Coulombic fission of droplets up to a critical radius into submicrometer droplets (Sauter mean of approximately 0.3 μm), measured by a laser diffraction analyzer. E.coli, on agar plates, is inactivated by this mist in a time and flowrate-dependent manner. We hypothesize that the observed antimicrobial effect correlates with the concentration of submicrometer droplets. The observed formation of submicrometer droplets from this volumetric DBD is similar to the bursting of droplets observed with electrospray devices using corona discharges.