The phenomena at unstable plasma-liquid interface

The local plasma-induced changes of liquid properties at the interface of microplasma and dielectric viscous liquid droplet in a narrow gap can lead to radial viscous fingering. The dynamics of the initiated microflow were investigated experimentally employing synchronized optical and electrical time-resolved measurements. Temporal development was studied for the whole event lifespan, focusing on the primary instability, fingering process and final fragmentation of the droplet. The extensive parametric study showed that the oil viscosity and the applied voltage amplitude were among the most influential parameters affecting the interface evolution. Furthermore, the introduced methodology enabled spatially resolved quantification of the dissipated power density and of the unstable plasma-liquid interface velocity, proving a strong correlation between them. After a discrepancy of experimental results for the high voltages and theoretical prediction of a known model was noticed, a modification of the model based on the change of the liquid viscosity with increased heating at high applied voltage amplitudes was proposed.