Characteristics of Molybdenum as a Plasma-Generating Electrode

Plasma technology is being studied and utilized in various medical fields, which requires increased ablation rate and decreased erosion rate of the metal electrode. The purpose of this experiment is to investigate the durability and the decomposition efficacy change in the catheter tips made of molybdenum metal. Metal particle size and amount in saline medium after plasma discharge were measured by electrophoretic light scattering photometry (ELS), and the tip metal surface after discharge was observed by field emission scanning electron microscopy (FESEM) and by the chemical reaction for component change. The mass defect in the tip and the decomposition rate of porcine disc by discharge time were measured by using the electric scale with a resolution of 50 mu g. The surface structure change on FESEM showed that the molybdenum tip was more intact than the stainless steel tip, and the surface components included Molybdenum 96.4 wt.%, Na 0.41 wt.%, and Cl 0.23 wt.%. The average size of the particles was 300 +/- 35 nm. At high level of electric power, the erosion rate of the molybdenum tip was about 1 ug/s. The erosion rate of the molybdenum catheter was 1x10(-13) kg per pulse, and the durability of the catheter tip was similar to that of the tungsten tip. Furthermore, we could generate plasma over 300 at the high voltage level with the molybdenum catheter. This means that the molybdenum catheter can effectively remove more tissue.