(170d) Experimental and Analytical Study of the Motion of a Liquid Slug and Ferrofluid in a Microchannel

In various microfluidic devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. By using a ferrofluid and electromagnet, the flow of a liquid or gas in a microchannel can be controlled by the magnetic force exerted on the ferrofluid. In this study, an unsteady motion of a liquid slug caused by the driving force from the ferrofluid has been investigated in a 200μm circular microchannel. The motion and behavior of the liquid slugs were observed. The surface tension and kinematic viscosity of the liquid were found to significantly affect the movement of the liquid slug. The velocity of the ferrofluid was in turn affected by the physical properties of the liquid pulled. Combinations of various liquids with the ferrofluid were examined in this study. The velocity of the ferrofluid was found to vary with the dynamic contact angle of the liquid slug. The movement and behavior of the interface between two different liquids were investigated experimentally and analytically. The interfacial shape changed continuously until the bidrops started to move. In addition, the interfacial tension of bidrops was estimated using the interfacial contact angle. We could relate the characteristics of the movement of bidrops to the interfacial variation.