Numerical Modeling of Droplet Splitting and Merging in a Parallel-Plate Electrowetting-on-Dielectric (EWOD) Device

Micro water droplet splitting and merging in a parallel-plate electrowetting-on-dielectric (EWOD) device has been studied numerically. The transient governing equations for the microfluidic flow are solved by a finite volume scheme with a two-step projection method on a fixed computational domain. The interface between liquid and gas is tracked by a coupled Level Set and Volume-of-Fluid (CLSVOF) method. A Continuum Surface Force (CSF) model is employed to model the surface tension at the interface. The physics of the fluid dynamics within the EWOD device has been examined. Contact angle hysteresis, which is an essential component in EWOD, is implemented together with a simplified model for the viscous stresses exerted by the two plates at the solid-liquid interface. The results of the numerical model have been validated with published experimental data. A parametric study has been performed in which the effects of channel height and several other parameters on the fluid motion have been studied.