Molecular dynamics study of electrocoalescence of pure water and salty nanodroplets

The mechanisms governing the electrocoalescence between droplets are intricate owing to the presence of many influential parameters. In this work, we conduct molecular dynamics simulations to explore the effects of electric field strength and ionic concentration on the electrocoalescence behaviors of one pure water droplet and one salty droplet. The dynamic evolution is difierent from that for two identical droplets. The electric field strengths are chosen near the critical value. When the electric field strength is less than the critical value, the coalescence process is similar regardless of the ionic concentration of the salty droplet. The analysis on the mobility of ions demonstrates that the diffusion time of ions is much longer compared to the characteristic time of deformation of the coalesced droplet. At a stronger electric field than the critical field, the coalescence behavior exhibits dependence on the ionic concentration. For cases of high ionic concentrations, a rebounding behavior between two droplets is identified due to aggregation of ions close to the contact region of the droplets. Further, we also investigate molecular interaction energy, hydrogen bonding and ejection of daughter droplets during the electrocoalescence. Our study reveals that the coupling effect between the electric field and the ionic concentration plays an important role in controlling the electrocoalescence behavior of droplets. (C) 2021 Elsevier B.V. All rights reserved.