Modeling Atmospheric Pressure Plasma Jets: Plasma Dynamics, Interaction with Dielectric Surfaces, Liquid Layers, and Cells.

Abstract

Atmospheric pressure plasma jets (APPJ) have many beneficial effects in their use in surface treatment and, in particular, plasma medicine. One of these benefits is the controlled production of reactive oxygen and nitrogen species (RONS) in the active discharge through the molecular gases added to the primary noble gas in the input mixture, and through the interaction of reactive species in the plasma effluent with the ambient air. As the effluent reaches the treated surface, benefits in addition to the reactive species are the ion flux and electrical field effects to the surface. Encouraging results have been obtained in plasma medicine, surface sterilization, deactivation of bacteria, and surface functionalization. The surfaces being treated by APPJs range from plastics to tissue to various liquids. In the case of APPJs in biological applications, the plasma-produced charged and neutral species in the plume of the jet often interact with a thin layer of liquid covering the tissue being treated. The plasma-produced reactivity must then penetrate through the liquid layer to reach the tissue beneath. Many of these aspects of APPJs as used in plasma medicine are computationally investigated in this thesis. Initially, the plasma discharge dynamics and production of RONS by multiple pulses of an APPJ into humid air was studied. Then, the effect that the permittivity of the material being treated has on the dynamics of the plasma discharge from the APPJ was studied. Next, a reactive water layer acting as the thin layer of liquid often found on wounds was used as the target of the APPJ. The subsequent formation of aqueous species from the interaction of the plasma jet touching and not-touching the water layer was investigated. Lastly, cellular structure was included in the underlying tissue beneath the liquid layer of varying thicknesses and the effect of the electric field produced by three different voltages of APPJ on the cells was investigated.