Size-dependent motion of bio-functionalized magnetic nanoparticle clusters under a rotating magnetic field

In this paper, we investigated the behavior of biofunctionalized, magnetic nanoparticle clusters under rotating magnetic fields in an aqueous solution to facilitate the use of such nanoparticles in biomedical applications. We found that two modes of motion for clusters of the nanoparticles exist. These two modes of motion exhibited by the clusters were rotation and oscillation, depending on the size of the cluster. Due to the interaction between the rotating magnetic field and the net magnetic dipole moment, the clusters were subjected to a forced vibration. A critical diameter range for the magnetic clusters was defined that may be used to distinguish between the rotation and oscillation of clusters. Furthermore, the characteristics of size dependence of the clusters' motion were also investigated.