Study of compound droplet dynamics and separation of immiscible liquids on EWOD DMF

This work reports the experimental study of the dynamics of micro-droplets composed of two immiscible liquids and their separation into constituent phases in response to electrowetting-on-dielectric (EWOD) digital microfluidics (DMF) actuation. Separating phases of a compound droplet without leaving any residue of one phase to the other is a big challenge but much needed for successful operations in many droplet-based microfluidics applications such as in liquid-liquid microextraction. In this study, such challenge is thoroughly addressed for the first time by addressing the role of viscosity ratio on the separation performance of two immiscible liquid phases. Also, quantitative analysis of compound droplet deformation has been performed.