Development and characterization of a linear cold atmospheric pressure plasma jet for large-area surface treatment

Abstract

Cold atmospheric pressure plasma jets are widely used for surface treatment and plasma-assisted processing. However, simultaneous plasma transport and spatial scaling remain challenging for existing plasma jet concepts. In this work, a novel linear-geometry cold APPJ concept based on a floating metallic mesh electrode integrated into a 3D-printed nozzle is developed to enable spatially extended plasma generation across the slit width of 36 mm and beyond. The plasma source comprises a primary discharge, which is formed between a high-voltage electrode and a metal mesh inside a quartz tube, and a secondary plasma phase. This secondary phase is generated at the opposite end of the metal mesh and propagates through a slit nozzle. The system was investigated under two gas atmospheres (Ar/H2 and Ar) and different substrate configurations, including conductive and non-conductive surfaces. Plasma propagation behavior was analyzed using high-speed imaging, while optical emission spectroscopy was employed to identify reactive species in both the primary and secondary discharge regions. Electrical characterization was performed to assess discharge behavior under representative operating conditions. The results demonstrate that the developed linear plasma jet enables stable plasma propagation across the nozzle width. Operation in Ar/H2 results in a more homogeneous plasma phase distributed across the entire width of the nozzle, whereas pure Ar leads to more localized discharge structures. The presence of hydrogen is expected to modify ionization kinetics, promoting more uniform plasma behavior. Furthermore, reactive species characteristic of both argon excitation and hydrogen-related processes were detected in the Ar/H2 plasma jet, indicating its suitability for applications requiring e.g. metal oxide reduction. Overall, the presented concept offers a promising approach to generating line-shaped plasma jets with enhanced spatial uniformity. This makes it particularly well-suited to large-area surface treatment applications, such as material modification and deoxidation processes.