Optical Imaging of Magnetic Particle Cluster Oscillation and Rotation in Glycerol

Magnetic particles have been evaluated for their biomedical applications as a drug delivery system to treat asthma and other lung diseases. In this study, ferromagnetic barium hexaferrite (BaFe [Formula: see text] O [Formula: see text]) and iron oxide (Fe [Formula: see text] O [Formula: see text]) particles were suspended in water or glycerol, as glycerol can be 1000 times more viscous than water. The particle concentration was 2.50 mg/mL for BaFe [Formula: see text] O [Formula: see text] particle clusters and 1.00 mg/mL for Fe [Formula: see text] O [Formula: see text] particle clusters. The magnetic particle cluster cross-sectional area ranged from 15 to 1000 [Formula: see text] m [Formula: see text] , and the particle cluster diameter ranged from 5 to 45 [Formula: see text] m. The magnetic particle clusters were exposed to oscillating or rotating magnetic fields and imaged with an optical microscope. The oscillation frequency of the applied magnetic fields, which was created by homemade wire spools inserted into an optical microscope, ranged from 10 to 180 Hz. The magnetic field magnitudes varied from 0.25 to 9 mT. The minimum magnetic field required for particle cluster rotation or oscillation in glycerol was experimentally measured at different frequencies. The results are in qualitative agreement with a simplified model for single-domain magnetic particles, with an average deviation from the model of 1.7 ± 1.3. The observed difference may be accounted for by the fact that our simplified model does not include effects on particle cluster motion caused by randomly oriented domains in multi-domain magnetic particle clusters, irregular particle cluster size, or magnetic anisotropy, among other effects.