Effect of liquid bridge evolution on the droplet non-coalescence under a DC electric field

The droplet non-coalescence characteristics and mechanism under a DC electric field are investigated by comprehensively using high-speed microscopic experiments, molecular dynamics simulations, and interface dynamics simulations. The researches show whether two droplets coalesce or not depends on the evolution of liquid bridge. The liquid bridge evolution is not only dominated by the electric force F-E and the capillary force F-i, but also slowed down by the viscous force. The relative strength of F-E and capillary force F-i relies on the electric capillary number Ca and the maximum liquid bridge radius R*(max). The droplet non-coalescence is more likely to happen as the Ca increases or the R*(max) decreases. Furthermore, the critical value Ca-c for droplet non-coalescence reduces as the R*(max) decreases. The ion transportation causes uneven distribution of ions and thus strengthens the F-E, resulting in the non-coalescence. These results provide significant guidance for efficient demulsification of water-in-oil emulsion.

Automated summary

The characteristics and mechanism of droplet non-coalescence under a DC electric field are investigated using high-speed microscopic experiments, molecular dynamics simulations, and interface dynamics simulations. The research shows that the evolution of liquid bridge determines whether two droplets coalesce or not. The evolution is influenced by the electric force F-E, capillary force F-i, and viscous force. The relative strength of F-E and F-i depends on the electric capillary number Ca and the maximum liquid bridge radius R*(max). The findings have significant implications for efficient demulsification of water-in-oil emulsion.