Molecular Dynamics Simulation On The Electro-wetting Behaviors Of Ionic Liquids

Compared with traditional aqueous solutions,Ionic liquids have important application prospects in the field of wetting and electro-wetting due to the advantages of high electric conductivity,long liquid range and low volatility.In this paper,molecular dynamics method was employed to investigate the wetting and electro-wetting?from E=0V/?to E=±0.18V/??behaviors of ionic liquid nano-droplet on a solid substratewith different adsorption capacities?from?=0.1kcal/mol to?=3.0kcal/mol?,as well as the distribution of ionic groups.The ionic liquid is 1-Butyl-3-methyl tetra-fluoroborate and coarse-grained to simplify the molecular simulation model.The results show that:When the droplet diffuses freely,the anion and cation groups are distributed in layers above the wall,and the peaks are different corresponding to different ionic groups;Due to the attraction of the solid substrate and the electrostatic force between anions and cations,the contact angle tends to increase slightly with the increase of ionic liquid pairs,the ionic electrostatic force gradually replaced the plate adsorption force;The contact angle decreases with the increase of the adsorption force of the plate,the ionic particles in the first wetting layer are loosely arranged on weak adsorption plate,and tightly arranged on strong adsorption plate,which leads to the continued increase in adsorption force is not easy to destroy the stable structure of first wetting layer.After the electric field is applied,ionic liquid droplet wets on the silicon solid wall to reach a new equilibrium state.The static contact angle decreases with the increase of the electric field strength,the ratio of the number of ions in the second wetting layer to that in the first wetting layer is consistent with the change trend of contact angle;The contact angle is asymmetric under the electric field with the same field intensity and different directions,?_postive<?_negative,and the value is about 10°;The wetting property of the droplet is more easily affected by the fluctuation of the electric field under the weak plate adsorption;The diffusion and contact angle of the droplet on the plate are mainly affected by the cationic distribution,the contribution of cations in the electrowetting process is greater than that of anions.Whether the plate or electric field plays a dominant role in the process of electrowetting depends on their respective strength.When the electric field strength is high,some ionic groups can be separated from the droplet and vaporize.