Magnetic Nanoparticles as Controlling Agents of Chain Structures in a Rotating Magnetic Field

Abstract

Chain formation in magnetic fluid has been observed under the influence of a rotating magnetic field. The influence on the chain flexibility and its rupture was studied by varying the frequency of rotation (1-5 Hz) of the magnetic field of a fixed magnitude (50 Gauss). Micrometer sized Fe3O4 particles and nonmagnetic expancel spheres of fixed concentration were later suspended in the magnetic fluid separately and their effect on the chain rotation dynamics was studied. It was observed that the critical frequency for the chain breakage was higher in the presence of larger magnetic particles compared to magnetic fluid alone. Non-magnetic particles formed chain structures in the presence of a static field but did not show any response to the rotation of the magnetic field. The established theory of magnetic chain formation was used to study and discuss the results by comparing the magnetic forces and viscous forces. The study may be useful for controlling chain length and flexibility in microfluidics.