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The addition of active trace components to non-thermal plasmas effectively enhances their chemical activity and has attracted considerable academic attention in the plasma community. It is essential to quantitatively estimate the effect of active addition on the properties of the plasma-surface interaction (PSI). In this study, we focus on the fundamental properties of dynamic surface charge of PSI by He-APPJ with 0~2% CF4 additive. The charge distribution measured by a reflective optical measurement platform based on linear electro-optic effect is calculated with a surface charge density inversion algorithm. Results show that a higher CF4 concentration can shrink the region of surface charge accumulation. Polarity effect was observed in aspects of maximum density when the CF4 concentration is gradually increased. The negative charge deposition is suppressed by the addition of CF4, nearly disappearing at 2% concentration. While the maximum density of positive charge rises to ~ 25 nC/cm2 at 0.5% CF4 before it decreases to ~10 nC/cm2. The dispersions of total surface charge at 0.5% and 1.5% additives indicate the unstable periodic bombardment of ionization waves in He/CF4 APPJ. The double effect of CF4 additive on the surface charges by He-APPJ is also discussed. These results provide fresh and deep insights into the interaction between dielectric surface modification and ionization waves that occurs in other plasmas processing fed with composite gases.

Low-temperature plasma ablation has been clinically used in minimally invasive surgeries. However, there is still a lack of research on its discharge process and ablation mechanism. This paper investigates the bubble generation process and micro-discharge phenomena of pin-to-pin surgical electrodes in NaCl solution driven by a high-frequency AC power supply at a level of (100–150) V. Microbubbles will occur around electrodes and merge to form a vapor layer that can completely cover the electrodes. Then, micro-discharges in the form of microspark would occur around the grounded electrode. The effects of geometrical and electrical parameters on the generation of vapor layers and micro-discharges are analyzed by the statistical results. It is found that the conductivity of the solution has an important influence on the generation probability and stability of vapor layers together with the occurrence position of micro-discharges. The simulation results of the discharge process and the experimental results match well with each other, and they demonstrate jointly that the discharge process is mainly influenced by the electrolytic effect.

This study introduces the design principle of a high-frequency square wave power supply, as well as the simulation and design process of a minimally invasive electrosurgical scalpel, which formed the low temperature plasma in saline solution. In order to verify the performance of the device, saline discharge experiments and pork ablation experiments were performed. An alternating high-frequency square-wave voltage was applied between coaxial double-layer electrodes with a spacing of 400 µm. The waveforms and amplitude of output voltage and current, conductance between electrodes, and output power were measured in saline discharge experiments. The results of pork ablation experiments with different power sources demonstrate that the device can generate low-temperature plasma for ablation rather than relying on thermal effects. The device can ablate pork under the driving of a 10 V, 100 kHz square wave voltage. In addition, the ablation speed and area will be greater with an increase in voltage or frequency.