Droplet motion in a microchannel: The influence of electrokinetic effects at liquid-liquid interfaces

Abstract

The electrokinetic effects at fluid interfaces can be utilized for droplet manipulation and separation in water, showing promising applications in areas such as oil-water separation and liquid-liquid extraction. In this study, numerical simulations are employed to investigate the impact of electrokinetic effects at the droplet surface and the horizontal interface between a non-conductive liquid and water on the electrokinetic velocity of a droplet within a microchannel. The findings indicate that as the magnitude of the negative zeta potential intensifies at the horizontal liquid-liquid interface, the flow velocity of non-conductive liquid gradually decreases and reverses direction when the zeta potential of the interface exceeds that of the channel wall. Conversely, the flow velocity of water continues to rise, resulting in an increased droplet movement velocity in water. The study also reveals that a lower water height and a greater non-conductive liquid height lead to faster water flow velocity and, consequently, a swifter droplet movement velocity. Additionally, the dynamic viscosity of the droplet has minimal impact on its electrokinetic velocity.