Simulation study on an atmospheric pressure plasma jet interacting with a single fiber: effects of the fiber's permittivity

Polymer fiber surface modification by low temperature plasma has received much attention in recent years. The plasma kinetic behavior and reactive species distribution can be totally different with the existence of fiber. In this work, a 2D axisymmetric fluid model is established to study the interaction between an atmospheric pressure plasma jet and a single fiber with different relative permittivity (epsilon (r) = 1.5 and 80, respectively). Division of the ionization wave is observed when approaching the fiber, followed by full wrapping of the fiber surface. Afterward, the ionization wave travels across the fiber and continues to propagate forward. Significant effects induced by the variation of the fiber's permittivity are observed. For the fiber with epsilon (r) = 1.5 the high electric field (EF) region shifts from the south pole (SP; closer to the jet tube) to the north pole (NP; opposite side to the SP), but the high EF region remains at the SP for the fiber with epsilon (r) = 80. This is due to the large potential difference on the surface of the fiber with epsilon (r) = 1.5. Furthermore, the time-averaged surface fluxes of the main ions (He+, N-2 (+), and O-2 (+)) and excited species (Hes, N, and O) are analyzed. It is found that the surface fluxes of the fiber with epsilon (r) = 80 at the NP are significantly higher than that of the fiber with epsilon (r) = 1.5. Therefore, increasing the relative dielectric constant of fiber would increase the main ions and excited species surface fluxes at the NP.