Ferrofluid droplet formation and breakup dynamics in a microfluidic flow-focusing device

This work aims at studying the expanding and breakup dynamics of the thread of a controllable dispersed phase under different flow rates in a microfluidic flow-focusing device. The whole formation process of ferrofluid droplets under no magnetic field (NM), a radial magnetic field (RM) and an axial magnetic field (AM) were investigated and compared. It was found that the volume of the ferrofluid droplets can be actively controlled by the applied magnetic field. The radial magnetic field and axial magnetic field affect mainly the expanding and breakup processes of the thread, respectively. The influence of the flow rates, magnetic flux density and magnetic field direction on the formation and breakup processes were extensively studied. The variation of the minimum width of the ferrofluid thread with the remaining time could be scaled with a power law.