Ignition process of the plasma scalpel in normal saline: Numerical simulation and comparison to experiment

Abstract

In this paper, the ignition process of the plasma scalpel is characterized by means of numerical simulation, shadowgraphy, and voltage–current measurements. The ignition process involves two phases: the pre-breakdown phase and the breakdown phase. Our study shows that in the pre-breakdown phase, the vapor layer is first generated around the corners of the active electrode and then gradually extends to cover the entire active electrode. Once the active electrode is fully covered by the vapor layer, the electric field reaches a maximum of 7.3 × 106 V m−1, which can cause discharge in the vapor layer. At this moment, the thickness of the vapor layer is approximately 100 μm. In the breakdown phase, the maximum electron density reaches 1018–1019 m−3. The plasma dissipates about 60% of the total power which is up to 125 W, thus enabling efficient cutting. In addition, we simulate the discharge characteristics of cutting various biological tissues. The results show that under the same voltage level, the higher the conductivity of biological tissues, the greater the discharge current. The biological tissues act as ballast resistors in equivalent circuits.