Visualizations of pH Change and Flow Field in a Liquid Induced by Irradiating Atmospheric Pressure Plasma Jet to the Liquid Surface

Abstract

For plasma-assisting cell modification, it is important to understand the mechanism of a transport process of plasma induced chemical species into a liquid suspending target cells. In this study, a plasma jet was irradiated to a liquid surface. The pH change and flow in the liquid induced by plasma irradiation were investigated. All experiments were conducted varying gas flow rate under same input voltage conditions. Two kinds of pH indicators with different color transition pH range were used as the sample liquid to visualize the pH change due to plasma irradiation. It was confirmed that the pH drop due to plasma irradiation can be mitigated by increasing gas flow rate. Particle image velocimetry (PIV) measurement revealed the improvement in stirring effect with the increase of gas flow rate. These findings would contribute to improve the quality of plasma-assisting cell modification. Furthermore, a combination of visualizations of pH change and flow field would be a useful method to explore the optimal conditions.