Visualization of Plasma-Induced Liquid Flow Using KI–Starch and PIV

The application of plasma jet interacting gel or liquid targets is widely researched and positive effects are obtained in biological experiments. To understand the working mechanism of plasma jet, the measurement of the spatial distribution of reactive oxygen species (ROS) is necessary. The authors have used potassium iodide (KI)-starch method, which uses reactions among KI, starch, and oxidative species, to visualize the distribution of ROS. Although our purpose focused on the 2-D distribution of ROS on the surfaces of liquid and agar regents, unexpected plasma-induced flow was also observed along the depth direction of the KI-starch liquid reagent. In this article, the plasma-induced flow generated by plasma jet was visualized with KI-starch, floating particle, and particle image velocimetry (PIV) methods, and the obtained results among the three observations were compared. The plasma-induced flow visualized by iodide-starch complexes in KI-starch method was similar to the flow of tracer particles in floating particle method. According to the analysis of PIV measurement, the velocity of the downstream was about 8 mm/s.