Array of 3D permanent micromagnet for immunomagnetic separation

Abstract

Immunomagnetic separation is the laboratory method used to separate targets from heterogeneous samples. It has been applied to separate or detect target entity existing rarely in the sample solution. In this study, a new type of microfluidic device with a 3D micromagnet array was designed, and it was demonstrated that this microfluidic device could be applied to immunomagnetic separation. As the 3D micromagnet is embedded in the microchannel, the height of the microchannel is extended to several hundred micrometers, and the magnetic field pulling the target can be confined to a limited region within the microchannel. Immunomagnetic separation using a microfluidic device was experimentally confirmed by fluorescence imaging. The capture efficiency was maximally 94.9% in the experimental study using the streptavidin-biotin binding of microbeads of the diameter of 1 µm. As a result, the microfluidic device with micromagnet arrays provides new solution for point-of-care device for immunomagnetic separation.

Magnetic Polymers for Magnetophoretic Separation in Microfluidic Devices

“…In the presence of an external magnetic field, IONPs (27 nm in diameter) accumulated around the micropillar along the direction of the flow and of the magnetic field, with a comet-like shape increasing over time. More recently, Bae et al integrated pillar-like permanent micromagnets made from a mixture of a hard ferromagnetic powder, neodymium oxide (5 µm nominal diameter), and PDMS [60]. The magnetic powder and the PDMS were mixed before filling the molds.…”

Recent advances in magnetic digital microfluidic platforms

“…Moreover, Y.M. Bae et al [75] designed a new 3D permanent magnet array, which allowed immunomagnetic separation in a magnetic DMF device (see Fig. 2C).…”

Laser-patterning of micromagnets for magnetophoretic biomolecule capture

“…Increasing capture magnetic beads size, though achievable in some cases, can result in issues with downstream processing, where the size of magnetic beads activity impedes further analysis or detection. Given this, many have instead elected to increase the gradient field within capture regions by the incorporation of micromagnets [15][16][17][18] , which generate highly localized field enhancement, drastically increasing magnetophoretic separation forces. This enhancement however is a near-field phenomenon (~um), rapidly decaying with distance away from the micromagnets 6,19 .…”

“…To date, the fabrication of micromagnets have been primarily dominated by thin film microfabrication approaches, with techniques including lift-off, electroplating, and inkjet printing 16,17,21 . Though notable alternative techniques have utilized soft magnetic composites for the generation of 3D micromagnets, these methods use lithographic processing to form initial molds defining micromagnet geometries limiting flexibility in device architecture 15,22 . Taken together, and in an ideal setting, micromagnet fabrication would be amendable for a range of device configurations, which in turn would allow for seamless integration of biomolecule capture systems with the number of processes that require pre-enrichment of biomolecules.…”