Experimental investigation of the motion of magnetic particles through high-viscosity fluids

In pulmonary diseases such as asthma, overproduction of mucus causes airway obstruction. Therapeutic efficacy of current medications remains poor because the mucus barrier poses a significant challenge to effective drug delivery. The presented work investigates the practicality of using vibrating or rotating magnetic particles (MPs ) to move drugs through high-viscosity fluids. Analytical calculations are used to predict the magnetic torque needed to oscillate or rotate barium hexagonal ferrite and iron oxide particles at frequencies from 5-300Hz in high-viscosity fluids ranging from 0.1 to 10 Pa·s. Vibration or rotation of MPs is achieved by wire coils specifically designed to fit within the sample plane of an optical microscope. Optical microscopy in conjunction with image analysis is used to quantify particle rotation and oscillation in hydroxyethylcellulose gel, corn syrup, and glycerol. Fluid viscosity is measured by a falling ball viscometer. Experimental results indicate that magnetic particles ranging from 20-500nm in size form 10μm aggregates in oscillating fields of 1-10mT in magnitude. This particle aggregation requires higher magnetic torques than initially estimated hampering the practicality of using vibrating or rotating MPs to deliver drugs through mucus.