Combining positive and negative magnetophoreses to separate particles of different magnetic properties

A new separation method that combines both positive and negative magnetophoreses based on ferrofluids is used to separate mixtures of particles with different magnetic properties. Ferrofluids are stable magnetic nanoparticles suspensions. Under external magnetic field gradients, particles with a larger magnetization within the ferrofluids are attracted to a magnet while the ones with a smaller magnetization are pushed away from it. Based on this principle, we report the design, modeling, fabrication, and characterization of the separation device and use it to separate magnetic and non-magnetic particles, as well as particles with different magnetizations. This scheme is simple, cost-effective, and label-free compared to other existing techniques.