Droplet impact on a hydrophobic surface integrated with electrowetting technique

Droplet impact on a hydrophobic surface can be controlled by varying the wettability of the surface. In the present work, the wettability of the surface is varied by applying alternating current electrowetting on a dielectric (AC EWOD), and the electrowetting-integrated droplet impact characteristics are analyzed for different frequencies, waveforms of applied voltages, and different sizes of droplets. A numerical technique with a dynamic contact model is developed to track the movement of the three-phase contact line in the electrowetting-integrated droplet impact process. The maximum spreading diameter of the droplet increases, and the recoiling of the droplet decreases with the increase in applied frequency at the first oscillation cycle of the droplet. Droplet spreading is more for the sinusoidal waveform than the triangular waveform. The impact of voltage frequency on the droplet spreading is more significant than the voltage waveform. The effect of electrowetting on the droplet impact is less for small-size droplets than the larger droplets. The electrowetting effect increases the dynamic wetting characteristics of the surface, resulting in enhanced spreading and reduced recoiling of the impacting droplet.