Control of Drop Impact and Proposal of Pseudo-superhydrophobicity Using Electrostatics

Abstract

The phenomenon of droplet collision with a charged substrate is investigated numerically by a coupled electro-hydrodynamic model. A charge conservation equation and Poisson equation are solved to obtain the transient electric field. The divergence of Maxwell stress (due to the electric field) is included in the transient momentum equation as a volumetric force to couple the electrostatic force with the hydrodynamics. The interface between the two phases is tracked by volume of fluid method. The motion of the contact line on the solid substrate is controlled by concentric ring shaped charged regions. The electric stress in the vicinity of the contact line restrains its motion in the desired direction, which changes the impact behavior substantially. A hydrophilic surface shows superhydrophobic characteristics when actuated by a sufficient magnitude of electric potential. The phenomenon is analyzed with different parametric variations like electric potential, wetting nature of the substrate, and velocity of collision as it is governed by the mutual interaction between the inertia, electrostatic, and capillary forces. The present method can be used to develop engineering surfaces with tunable wetting nature.