Interaction between atmospheric pressure plasmas and non-planar dielectric surfaces in humid air DBD

Abstract Dielectric barrier discharges (DBDs) have showed great advantage for surface treatments in many application fields. In a common scenario, surface to be treated was dielectric that covered the electrode and acted as part of the discharge circuit, therefore the surface properties such as permittivity, conductivity, and morphology could affect the discharge dynamics, which remained an active researching area. In present study, systematic investigations were conducted on the discharge mechanism in humid air DBD with one of the dielectric surfaces being non-planar, and the combination effects of surface morphology, voltage polarity, surface electrical properties were highlighted. A 2-dimentional plasma hydrodynamics model was constructed, and validated with experiment observation. Results showed that when the non-planar surface acting as the cathode, uniform surface discharge was apt to be emerged, and consequently leading to higher and more uniform distribution of reactive species fluences towards the non-planar surface with comparison to the cases of acting as anode. In the cases with uneven protrusion height, discharges would be preferentially formed on the crests of higher protrusions, and tended to inhibit the discharges on the adjacent lower ones. Additionally, effects of the protrusion’s height, non-planar dielectric’s permittivity and conductivity were discussed with focus on the discharge dynamics and reactive species fluences towards the non-planar surface. Noted that the surfaces to be treated in reality were generally non-planar on the spatial scale of millimeter such as human skins, or micrometer scale such as unpolished dielectric surfaces, findings in present work will contribute to an extended understanding of plasma-surface interactions from both physics and application perspectives.