Plasma DBD Electrodes

Abstract

As a novel alternative for conventional seed disinfection methods, a new design has been proposed in this report using a surface dielectric barrier discharge (SDBD) fractal electrode. The discharge mechanism for this electrode is a diffuse microdischarge under AC or short-pulsed DC mode operation. In this way, cold plasma could be generated that is applicable for seed disinfection. Furthermore, the electrodes were designed to be part of a proof of concept fluidized bed reactor with a reactor size of 10×20×20[𝑐𝑚] for disinfecting cabbage seeds with a diameter of 2𝑚𝑚. Because of this application, the efficacy of seed decontamination using plasma with its generated reactive agents was discussed. The used gas mixture in which the electrodes created plasma was ambient air without increased humidity. This means that the main reactive agents for sterilisation are reactive oxygen species (RON) like ozone (O3) and reactive nitrogen species (RNS). The electrical and physical parameters required to make cold-plasma were investigated to come up with a proper design for the electrode. From this theoretical analysis, five different initial designs emerged. The analysed designs include a wire-to-wire, wire-to-sheet, multi-hollow DBD, fractal SDBD and a coplanar DBD fractal electrode. All electrode designs were made based on the state-of-the-art dielectric barrier discharge principle. Moreover, in the design consideration, different materials for the conductor and dielectric were discussed, mainly based on electrical properties, plasma generation and manufacturing possibilities were considered. Based on previously set trade-off requirements, together with the results of measured power and turn on voltage of the plasma electrodes, the best designs tested design for seed disinfection are the double-sided 5𝑡ℎ order Hilbert fractal with a 1.6 𝑚𝑚 barrier and the single-sided 5𝑡ℎ order Hilbert fractal with a 0.8 𝑚𝑚 barrier.