The field of microfluidics is developing with advances in biotechnology and μ-TAS technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. By using a ferrofluid, the flow of a liquid or gas in a microchannel can be controlled by the driving power exerted on the ferrofluid. In a previous study, an unsteady flow of a liquid slug caused by the driving force exerted by the ferrofluid was investigated in a 200μm circular microchannel. The velocity of the ferrofluid was found to be affected by the physical properties of the liquids being pulled, such as the dynamic and static contact angles, surface tension and kinematic viscosity of the liquid slugs. At sufficiently high velocities of the ferrofluid, emission of a liquid droplet from the liquid-liquid interface was observed. In the present study, combinations of various liquids with the ferrofluid were examined in two microchannels (130μm and 200μm diameter). The relationship between the emission of liquid droplets and interfacial fluctuation of the bidrops was investigated experimentally and analytically. The emission of liquid droplets from the interface and behavior of the interface were observed using liquids of different viscosities. The interfacial shape changed continuously until a liquid droplet was emitted from the interface of the immiscible liquids. When the ferrofluid velocity was increased, necking of the liquid-liquid interface occurred continuously and some liquid droplets were emitted from the interface. We could study the characteristics of emission of liquid droplets from the interfacial variation.
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