A Numerical Study on Electrowetting-Induced Droplet Detachment From Hydrophobic Surface

Abstract

Electrowetting-induced microwater droplet detachment from hydrophobic surface has been studied numerically. The governing equations for transient microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The free surface of the droplet is tracked by the volume-of-fluid method with the surface tension force determined by the continuum surface force (CSF) model. The static contact angle has been implemented using a wall-adhesion boundary condition at the solid–liquid interface, while the dynamic contact angle is computed assuming a fixed deflection from the static contact angle. The results of the numerical model have been validated with published experimental data and the physics of stretching, recoiling, and detachment of the droplet have been investigated. A parametric study has been performed in which the effects of droplet volume, voltage amplitude, and voltage pulse width have been examined.