Freeze‐Casting of Surface‐Magnetized Iron(II,III) Oxide Particles in a Uniform Static Magnetic Field Generated by a Helmholtz Coil

Research is conducted into freeze‐casting of surface‐magnetized Fe 3 O 4 particles under uniform, low‐strength magnetic fields (5.2 mT) to mimic the mechanical characteristics of natural human bone. Freeze‐casting is a technique that fabricates porous materials by directionally freezing and sublimating an aqueous slurry. A novel, Helmholtz coil‐based freeze‐caster is developed and it is shown that, during freeze‐casting, the use of this Helmholtz coil generates a more uniform magnetic field than permanent magnets. This uniform magnetic field, applied in the direction of ice growth, keeps particles from agglomerating and results in an increase of 55% in both the ultimate compressive strength and the elastic modulus of porous surface‐magnetized Fe 3 O 4 scaffolds. These increases can be linked to a reduction in the porosity that occurs due to magnetic interactions between particles in the presence of the field. These results offer a novel method for the fabrication of bone‐inspired biomaterials and structural materials.