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Tunable Superparamagnetic Ring (tSPRing) for Droplet Manipulation

Authors:
V. Nasirimarekani, F. Benito-Lopez, L. Basabe-Desmonts
Year:
2021
Journal:
Adv. Funct. Mater.
Impact Factor:
19924
Quartile:
D1-Q1
Volume:
2100178
Initial page - Ending page:
1 - 8
ISBN/ISSN:
1616-3028
DOI:
https://doi.org/10.1002/adfm.202100178
Description:

The manipulation of droplets by magnetic field forms the basis of a fascinating technology that is currently in development. Often, the movement of droplets with magnets involves adding magnetic particles in or around the droplet; alternatively, magneto responsive surfaces may also be used. This work, presents and characterizes experimentally the formation and properties of a tunable superparamagnetic ring (tSPRing), which precisely adjusts itself around a water droplet, due to liquid-liquid interaction, and enables the physical manipulation of droplets. The ring is made of an oil-based ferrofluid, a stable suspension of ferromagnetic particles in an oily phase. It appears spontaneously due to the oil-water interfacial interaction under the influence of a magnetic field. The ferrofluid-water interaction resembles a cupcake assembly, with the surrounding ring only at the base of the droplet. The ring is analogous to a soft matter ring magnet, showing dipole repulsive forces, which stabilizes the droplets on a surface. It enables robust, controllable and programmable manipulation of enclosed water droplets. This work opens the door to new applications in open surface upside or upside-down microfluidics and lays the groundwork for new studies on tunable interfaces between two immiscible liquids.