Figure 2.

Separations of paramagnetic hydrogel spheres from diamagnetic hydrogel spheres using rare-earth magnets. A) A set of schematics—three-dimensional, side-view, and top-view—illustrating the method of separation used in (B)–(D) in which the magnets contact the spheres in solution. B) An optical image of the initial mixture of paramagnetic CMC spheres (white, Ho³⁺) and diamagnetic AA spheres (gray, Al³⁺) placed in a glass chamber (A). B–D) Upon immersion of a magnet in the mixture, the paramagnetic spheres were strongly attracted to the surface of the magnets, from which they were transferred selectively to a second chamber. The dotted white line highlights the glass divider separating the two chambers. E) A schematic illustration of the second type of separation, in which a magnet was placed under the dish where it does not contact the spheres. F–G) Optical images of the mixture of paramagnetic AA spheres (gray, Ho³⁺) and diamagnetic CMC spheres (white, La³⁺) in a Petri dish (E) before and after separation by an external rare-earth magnet.