Response of a magnetic particle to rotating magnetic field in viscoelastic fluid.

Abstract

The rotational dynamics of a freely suspended ferromagnetic particle in a viscoelastic fluid subjected to a rotating magnetic field are studied both experimentally and theoretically. Our results reveal that when the characteristic relaxation time of the fluid is much smaller than the inverse of a critical field frequency, the particle's rotational behavior resembles that in Newtonian fluids. Increasing the relaxation time enhances the time-averaged rotation frequency of the particle undergoing asynchronous rotation. Moreover, the critical frequency is shown to scale linearly with the magnetic field intensity and inversely with the fluid's zero-shear viscosity. Our work is expected to guide precise manipulation of ferromagnetic particles in biomedical systems where viscoelastic environments dominate.