Microscopic mechanism of nanofluids electrospray: A molecular dynamics study

Abstract

Cone-jet electrospray is widely used in various fields, such as electrospinning, nanostructured porous coating preparation, and inkjet printing, for which it can produce a large number of monodisperse and high charge-to-mass ratio droplets. A molecular dynamics method is employed to investigate the cone-jet electrospray emission behavior of nanofluids, where the microscopic mechanism of cone-jet electrospray including the formation of the cone, disintegration of the jet, stability of hydrogen bond, and interactions between molecules is revealed. In this paper, the influence of operating parameters and liquid physical properties were numerically conducted and extensively analyzed. The results show that the cone-jet electrospray only occurs in a certain range of applied voltage and flow rate, and the temperature and concentration of nanoparticles have a great effect on the jet length and the number of clusters produced by jet disintegration. When the electric field intensity increases, the length of the jet and the number of clusters increase. However, regardless of the electric field intensity, the maximum axial density is always located near the capillary outlet and the maximum radial density is located at the central axis of the capillary. As the temperature increases, the number of clusters increases significantly due to the synthetical effect of electric field-induced disintegration and evaporation, whereas the jet length is reduced. With an increase in concentration of nanoparticles at room temperature, the Taylor cone not only appears earlier but also has a larger angle. Meanwhile, the non-bonded interactions between ethanol molecules become stronger. This work provides microscopic mechanisms of nanofluids cone-jet electrospray and is potentially useful to optimize the design parameters of industrial applications.