Modeling Ferrofluids in Spatially-traveling Sinusoidally Time-varying Magnetic Fields

Ferrofluids are stable colloidal suspensions of nanosize ferromagnetic particles in either an aqueous or an oil-based solvent1. In the presence of a magnetic field gradient within a ferrofluid, magnetic forces and torque are developed to drive magnetic particles, which subsequently draw along the liquid solvent carrier. This allows continuous actuation and precise positioning of the ferrofluid using a magnetic field. Ferrofluids have found their way into a variety of applications, such as sealing, damping2 and blood separation3. In this study, we present a numerical method to simulate the dynamics of ferrofluids in spatially-traveling, sinusoidally time-varying magnetic fields. Actuation using traveling waves involves magnetic body forces and torque on the magnetic moment of nanoparticles, both of which affect the overall pumping.