Active generation of multi-component droplets using microfluidics under magnetic field influence

Microfluidic technology can be used to generate multi-component droplets. If the multi-component droplets contain ferrofluid, the droplet generation process can be controlled using a magnetic field. Here, we demonstrate for the first time an active method for generating two-component magnetic droplets using microfluidics with a flow-focusing configuration under the influence of a transverse magnetic field. The two-component droplet consists of a non-magnetic fluid core surrounded by a magnetic shell. The results of the study show that using a magnetic field allows for significantly increased flexibility in controlling the structure of two-component droplets. When using a magnetic field, the volume of the droplet's magnetic shell depends not only on the volumetric water flow rate in the chip, V2 ∼ Q1−1, but also on the magnetic field gradient, V2 ∼ ∇H−1. At low water flow rates in the chip, disturbances that develop on the jet surface under the action of the magnetic force play a key role in ferrofluid dispersion. However, with increasing water flow rate, the influence of the magnetic force degenerates. The results obtained in this work open up new possibilities for the creation of soft magnetic robots that can be used to move cargo.