Diamagnetic levitation with permanent magnet microarrays for precise contactless guiding and trapping of micro-droplets and bioparticles in fluids

摘要

Diamagnetic levitation was applied to micro-positioning and trapping of diamagnetic micron-sized beads, micro-droplets and bioparticles. Considering scale reduction laws for magnetism, it appears that diamagnetism is highly efficient for magnetic MEMS. It is demonstrated that diamagnetic bodies can be contactless guided along magnetic channels or trapped into magnetic wells both in air or liquids. Levitations of water or oil microdroplets were shown within a 1.6mm bore of a cylindrical magnet (Fig. 1). New structures were designed, fabricated and tested, either micromachined in bulk magnets (Fig. 2) or electroplated on silicon wafers (Fig. 3). The levitation of micro-droplets of about 30μm in diameter was achieved inside 100-μm wide trenches machined by electro-erosion in permanent magnets (Fig. 4). A low-cost mass production technique with thick permanent micromagnets electroplated above silicon was also implemented into various matrix configurations. The devices were tested with diamagnetic latex microbeads of mean diameter 3μm in a paramagnetic buffered solution. Trapping and arraying of microparticles in stable spatial levitation within magnetic wells were successfully achieved (Fig. 5). Contactless passive levitation brings amazing possibilities to bio-chips, including fast arraying of unlabelled cells or microbeads on micro-magnets, and contamination-free biochemical micro-reactors.