Study on the Discharge Characteristics of Flexible Long-Tube Plasma Jet

Atmospheric-pressure low-temperature plasma jets have demonstrated significant biomedical potential due to the abundance of active species. Flexible long-tube plasma jets were developed to deliver plasma to the internal organs through the gastrointestinal tract. This study investigates the effects of discharge operation parameters (voltage and gas flow rate), electrode configurations, and the tube materials on the discharge characteristics and propagation of plasma jets. Experimental results reveal that increasing both the voltage amplitude and the gas flow significantly enhances the propagation length of the plasma plume. Additionally, the single-needle electrode structure enables longer plasma transmission compared to needle–ring configurations. The measurement of the emission spectra at various positions indicates that the emission intensities decrease gradually with the increase in propagation distance. Among the tested tube materials—polyurethane (PU), polyethylene (PE), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC)—PU is found to allow the greatest plasma plume extension. Optimization of these parameters enables the delivery of the plasma jet with a length of 90–100 cm, providing the potential for advanced biomedical interventions.