Analysis on asymmetric current of plasma mediated electrosurgery

Abstract

Asymmetric current, which is induced by the plasma during medical procedures, is investigated in the environment analogous to surgical situation. Many electrosurgical devices include DC-blocking capacitors to eliminate direct current component. However, the plasma generated between the electrode and biological tissues create asymmetric current resulting in the electrical stimulation. In this Letter, the current was significantly reduced by changing the ionization condition through using Ar or He gas and decreasing the velocity for a tissue movement. In the radiofrequency discharge, the difference of secondary electron emission coefficient causes asymmetric peaks, but the condition influences that the plasma stays in α-mode and the current is symmetrically changed. Furthermore, the electrons are also accelerated by the potential drop near the cathode surface, and the potential drop for Ar is two to third lower than the one for?? N??_2. When Ar and He gas was supplied to the gap, the ionization of the low potential drop for Ar gas is dominated in the bulk plasma, but the air plasma has high energy electrons to ionize the gas on the sheath plasma and change to γ-mode easily. These characteristics provide symmetric current to medical procedures thus eliminating the electrical stimulation and achieving safer method.