Single-Ring Magnetic Levitation Configuration for Object Manipulation and Density-Based Measurement.

Magnetic levitation is a recent research hot spot; however, most of the extant configurations use two magnets with like poles facing each other. This paper proposes a novel magnetic levitation configuration that is based on a single ring magnet, and this configuration opens a wide operational space that enables object manipulation and density-based measurement. We develop a mathematical model to calculate the magnetic field around the magnet and to numerically correlate the levitation height and density of the object. Experimental results prove that this novel configuration can achieve a high accuracy (±0.0005 to ±0.0078 g/cm) in density measurement for small-sized (∼5 μL) samples. It can manipulate particles, powders, and oil droplets effectively without any direct contact, and it has high sensitivity in the separation of multiple diamagnetic objects with slight differences in densities as well. The accuracy and sensitivity of the proposed configuration are both higher than those of the extant configurations. All of these results are expected to promote deeper study and applications of the magnetic levitation configuration in the field of density-based characterizations and manipulations.