Thermal analysis and design optimization of a bipolar CAP nozzle via iterative prototyping

This thesis presents the thermal evaluation of the first prototypes of ParoDüse, a flexible bipolar cold atmospheric plasma (CAP) nozzle, developed through an iterative design and testing process. The final application envisioned is the treatment of periodontitis, which requires the nozzle to come in direct contact with oral mucosa. Therefore, thermal safety requirements set the general aim of the optimization process: temperature of both nozzle and effluent shall remain below 41°C. Across three successive design generations, key geometric parameters—including inter-electrode distance, gas channel width, and the position and shape of the gas outlet—were systematically modified to investigate their influence on the nozzle’s thermal behavior during operation. In parallel, the experimental setup for temperature measurement was progressively optimized, enabling more reliable and consistent comparisons between prototypes. The final design generation exhibited improved thermal performance, particularly in terms of reduced nozzle surface temperature. Moreover, the refined measurement setup allowed for the formulation of a hypothesis, grounded in experimental data, suggesting a correlation between the plasma’s visual characteristics and the nozzle’s surface temperature. These findings mark a significant step forward in the development of a fully functional bipolar CAP nozzle. With the ultimate goal of treating periodontitis, future work will focus on evaluating the antibacterial efficacy of the device.