Unravelling Electrostatic Actuation on Inclined and Humped Surfaces: Effect of Substrate Contact Angle

Abstract

Application of external electric field has become a well-established technique to achieve dynamic wetting over a flat surface on which the drop is resting. However, an increase in electric field can overcome the gravitational pull and the drop can climb the substrate against contact-line friction. The present study investigates droplet up-climbing for different wettability regimes using the energy minimization method. We proposed a capacitive network around an up-climbing drop for evaluation of the resultant force on it. This method captures the influence of the orientation and geometry of the surfaces on the droplet motion. Motive forces for dynamic wetting and velocity over inclined surfaces (15–75°) are predicted. Furthermore, over a humped surface, a voltage map is obtained for steady droplet motion. Variation of the voltage map for different equilibrium contact angles of the hump is also presented. A one-dimensional momentum balance equation is used to predict the temporal location of the drop and th...