Manipulating the Interfacial Tension and Viscoelasticity of Droplets with Superparamagnetic Nanoparticles: Role of Magnetic Dipole Interactions

Interfacial tension and viscoelasticity are basic properties of droplets and are greatly important in droplet science. However, the droplet interface presents complexities in both the time dimension and spatial domains, and manipulating interfacial tension and viscoelasticity remains a significant challenge, which is crucial for achieving high emulsification efficiency and droplet stability. Herein, the fundamental principle of interfacial tension and viscoelasticity is emphasized, and the interfacial properties were shown to be directly manipulated by magnetic dipole interactions. At the single-particle level, we manipulated the interfacial tension by regulating the assembly nanopatterns of superparamagnetic nanoparticles (MNPs), which is associated with the magnetic dipole interactions between adjacent MNPs, through variations in the MNP shape at the interface. At the particle population level, we modified the magnetic dipole interactions between MNP chains by adjusting the concentration, which allowed us to design the assembly network at the interface for manipulating the viscoelasticity of droplets.