Axial magnetic levitation: A high-sensitive and maneuverable density-based analysis device

Abstract Magnetic levitation (MagLev) is an emerging technology that levitates materials in paramagnetic media, yet standard MagLev devices that are based on two identical square magnets grants limited operational space and applicability. This study focuses on the axial MagLev configuration, which are based on two identical ring magnets. The approach offers larger operational space as well as greater maneuverability. A unified mathematical model was developed to calculate the distribution of the magnetic field in the axial MagLev configuration, and to correlate the levitated samples’ densities and equilibrium positions along the centerline without knowing the samples’ weight or volumes. With the mathematical model, the sensitivity of the measurement is predictable and adjustable without the restriction of the linear magnetic field along the centerline. The sensitivity of the axial MagLev device can be increased by ∼ 20 x, i.e., from 66 to 1450 mm/(g/cm3), when the separation distance of magnets is increased from 8 to 32 mm. To demonstrate the potential for the wide applicability, density measurement of living cells, defect detection of polymeric products, as well as a combination of axial MagLev and ultrasonic measurement approach are carried out. The proposed method has prospects for broad applications in areas such as biomedicine, material science, and measurement engineering.