Silica shell cemented anisotropic architecture of Fe3O4 beads via magnetic-field-induced self-assembly

Fe3O4–SiO2 beads with diameters in the range of 200–550 nm were self-assembled into stable quasi-one-dimensional superstructures along the direction of an external magnetic field. The SiO2 shells, working as “cement”, coalesced with each other and formed immobile linkages between adjacent Fe3O4 “bricks” and preserved the anisotropic structures. Additionally, the resultant quasi-one-dimensional structures can be oriented in an applied magnetic field, which makes them ideal candidates for functional devices such as magnetic microstirrers and magnetic switches.