Plasma

In this work, the forces on millimeter-sized test spheres were measured to understand charging and field forces in a surface DBD. Spheres rolling on a tilted diffuse coplanar surface barrier discharge (Dcsbd) were observed to accelerate more slowly when the discharge was ignited. Additionally, a force towards the surface was measured. By modeling the rolling dynamics, the lower acceleration can be explained by this force. The inhomogeneous electric field above the Dcsbd is responsible for this effect. The electric field pulls the spheres towards the electrodes via a polarization force. Electrostatic simulations of the observed situation reproduce the correct order of magnitude for this effect.

Biofilm formation on material surfaces represents a major challenge in many technological and biomedical applications, particularly in confined geometries such as tubes and channels. In this study, the antibacterial performance of a surface dielectric barrier discharge system with liquid electrodes was investigated to develop a plasma-assisted approach for inactivating bacterial biofilms on internal surfaces. The discharge operated along the inner surface of the dielectric tubes as it was gradually filled with water. This configuration created a dynamic plasma–liquid environment in which plasma filaments propagated along the treated surface, while reactive species were produced simultaneously in both the gas and liquid phases. The formation of reactive oxygen and nitrogen species in plasma-treated water was characterized, and its antimicrobial activity was evaluated against planktonic Escherichia coli CCM 3954. The effectiveness of both plasma-activated water and direct plasma exposure in inactivating E. coli biofilms grown on the inner surfaces of polymer tubes was also investigated. The results demonstrate that the investigated surface dielectric barrier discharge configuration enables simultaneous direct plasma treatment and in situ generation of plasma-activated water. This approach shows promise for plasma-assisted decontamination of tubular materials and confined systems, where conventional disinfection methods may be limited.

Experimental measurements and two-dimensional axisymmetric fluid simulations are performed to study coaxial argon dielectric barrier discharge. Oscilloscope measurements capture voltage–charge waveforms and Lissajous figures to resolve cycle-integrated electrical characteristics. Continuous-integration optical emission spectroscopy without phase resolution is used to qualitatively verify metastable argon. As peak voltage rises from 5 kV to 13 kV, the simulated volume-averaged electron temperature displays a pronounced N-shaped trend: it peaks at 9 kV, falls abnormally between 10 kV and 11 kV, and recovers at higher voltages. This non-monotonic variation arises from intra-cycle self-shielding by dielectric surface charges together with power-broadening driven by discharge spatial expansion. Monotonically increasing equivalent capacitance confirms continuous surface charge accumulation, and the simulated inward shift of the high-electron-temperature region validates the emergence of surface-charge-induced reverse electric fields. The discharge maintains a steady filamentary regime across all tested conditions. Because microdischarge filaments occupy only a small portion of the gap, the volume-averaged electron density from simulations is far lower than the peak density within individual streamers. This work elucidates the mechanism underlying the anomalous electron temperature drop at moderate voltages and offers guidance for controlling atmospheric-pressure filamentary DBD.