Ferrofluids, formed by magnetic nanoparticles uniformly dispersed in a liquid carrier, respond to an external magnetic field, which enable the fluid＇s position by applying a magnetic field. Here, ferrofluids composed of Fe3O4 nanoparticles with oleic acid and oleylamine as the surfactant and photoresist, respectively, were prepared. Under an external magnetic field, the movement and the position of ferrofluids and the injection of the fluids into complex shapes were easily achieved. The ferrofluid surfaces were distorted under the magnetic field, and the surface structue was controlled by the applied field strength. Using a photoresist as the liquid carrier, it was possible to solidify the ferrofluids by UV irradiation. The shape and the position of the solid superparamagnetic nanoparticles/polymer composites were also determined by the external magnetic field.
