Many complex dynamics and anisotropic structures in living organisms and biological tissues can be mimicked by using magnetic colloids confined to air-liquid or liquid-liquid interfaces [1], droplets of a magnetic liquid in an immiscible fluid [2] or iron microparticles in polymeric matrices containing human mesenchymal stem cells [3].

Ten years ago our research group started a set of research projects towards the fabrication of an unprecedented magneto-rheoconfocal device that has recently come to fruition. The device is capable of generating highly-controlled non-stationary magnetic fields in the time and space domains with frequencies upwards of 4 kHz in millimetric three-dimensional volumes, while the collective dynamics are visualized using high-resolution and high-speed confocal microscopy. The device can also generate synchronized fields by delicately balancing the field magnitude and homogeneity.

In this communication we first show some remarkable examples of emergent dynamics and biomimetic 3D structures. We explore multiple time-dependent schemes, including triaxial, precession and toggled magnetic fields, giving rise to a rich variety of structures with tuneable properties, including their rheological response. Phase diagrams can be outlined describing the dependence of the type of structure on field scheme, frequency, and strength. Finally, we employ these emergent structures in the synthesis of magnetic hydrogels doped with living cells. These promising magnetic biomaterials can serve as scaffolds for cell growth, while demonstrating a good magnetorheological response.


References:
[1] Nat. Matter 10 (2011) 698-703
[2] Soft Matter 10 (2014) 9136-9142
[3] Smart Mater Struct 30 (2021) 065015

Unsteady magnetic fields,Non-stationary fields,Emerging systems,Magnetic hydrogels,Biomaterials