Improvement of Measurement Performance in Density Through Magnetic Levitation Using Asymmetrical Cylindrical Magnets

Negative magnetophoresis-based magnetic levitation (MagLev) is a label-free and simple method to levitate and manipulate nonmagnetic materials, which is a recent research topic of interest in density-based analyses. However, the existing MagLev mainly uses two permanent magnets with a longitudinal symmetry structure, facing difficulties in achieving both a large measurement range and high measurement sensitivity simultaneously. To solve this, a novel asymmetrical cylindrical MagLev configuration is proposed involving two cylindrical magnets with different thicknesses. On this basis, the characteristics of magnetic force at different magnet spacings are investigated, and the levitation behavior of the samples with different densities is explored. According to the numerical and experimental results, it is interestingly found that two different continuous functional regions with inward radial magnetic forces can be formed for density measurement by adjusting the magnet spacing. The functional measurement regions at small magnet spacing and large magnet spacing serve a large measurement range and a high measurement sensitivity, respectively. Importantly, the measurement range and sensitivity in the new MagLev are both better than conventional MagLev. These findings are of significance to understanding the MagLev process and to promote its practicality.