Molecular dynamics simulation on evaporation of water and aqueous droplets in the presence of electric field

Abstract

The study on evaporation of water droplet with dissolved salt is important for the understanding of electrospinning and electrospray mass spectrometry experiments. In this work the dynamics of evaporation of water droplet and aqueous droplet with dissolved either LiCl, NaCl or KCl salt in the absence and presence of a homogeneous electric field are comparatively studied by molecular dynamics simulations. The results show that (1) the evaporations of water and aqueous droplets are all accelerated by applying an electric field; (2) the aqueous droplet evaporates slower than the water droplet at low electric field of 0.4Vnm−1, however, its evaporation rate is enhanced significantly and exceeds the water droplet at high electric fields of 0.6 and 0.8Vnm−1; (3) aqueous droplet with dissolved KCl molecules evaporates the fastest, and then followed by dissolved NaCl and LiCl molecules; (4) an optimal salt concentration is observed for the aqueous droplet, above which the evaporation rate is reduced significantly and may cause a electrospinning failure. The present results are qualitatively agree with the observations in the electrospinning experiment and are attributed to the fact that the electric field applied causes the droplet deformation, directional arrangement of water molecules along the electric field direction, acceleration of water molecules due to ions acceleration, as well as hydration effect.