Statics and dynamics of nanodroplet electrowetting on an isothermally heated nanostructured surface

• Published in: Journal of molecular liquids 2021-11, Vol.342, p.117468, Article 117468
• Main Authors: Zhang, Ben-Xi, Wang, Shuo-Lin, He, Xin, Yang, Yan-Ru, Wang, Xiao-Dong, Lee, Duu-Jong
• Format: Article
• Language: English
• Subjects: Electrowetting; Evaporation; Hydrogen bonds; Nanodroplet; Pinning
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.117468

•Spreading of nanodroplets on isothermally heated textured surfaces is studied.•A vertical electric field is imposed on droplets during spreading.•Field strength and direction and surface wettability and temperature are focused.•Two special effects induced by high substrate temperatures are identified. The statics and dynamics of electrowetting of a water nanodroplet on an isothermally heated nanostructured surface subjected to a vertical electric field are investigated via molecular dynamics (MD) simulations. The simulation results reveal that when imposing a constant electric field on the water nanodroplet, the static and dynamic contact angles of the water nanodroplet are always decreased with increasing the substrate temperature. At the same time, the spreading becomes faster at higher substrate temperatures. In the no-temperature-difference scenario, the statics and dynamics of electrowetting are found to strongly depend on the field strength and direction owing to small droplet sizes. Intriguingly, this dependence weakens with increasing the substrate temperature even completely disappears at high enough substrate temperatures. The result in the finite-temperature-difference scenario can be attributed to the weakened pining effect caused by vigorous evaporation in the vicinity of the contact line as well as the decreased liquid–vapor interfacial tension (or increased spreading coefficient) arising from the elevated interface temperature.