Manipulating particles and cells in magnetic liquids through “negative magnetophoresis” is a new research field. It has resulted in label‐free and low‐cost manipulation techniques in microfluidic systems and many exciting applications. It is the goal of this review to introduce the fundamental principles of negative magnetophoresis and its recent applications in microfluidic manipulation of particles and cells. The theoretical background of three commonly used specificities of manipulation in magnetic liquids is first discussed, including the size, density and magnetic property of particles and cells. This is followed by a review and comparison of the media used in negative magnetophoresis, which include paramagnetic salt solutions and ferrofluids. Afterwards, the existing microfluidic applications of negative magnetophoresis are reviewed, including separation, focusing, trapping and concentration of particles and cells, determination of cell density, measurement of particles' magnetic susceptibility, and others. The need for developing biocompatible magnetic liquids for live cell manipulation and analysis and its recent progress are also examined. Finally, the review is concluded with a brief outlook for this exciting research field.
Magnetophoresis is an important physical process with application to drug delivery, biomedical imaging, separation, and mixing. Other than empirically, little is known about how the magnetic field and magnetic properties of a solution affect the flux of magnetic particles. A comprehensive explanation of these effects on the transport of magnetic particles has not been developed yet. Here we formulate a consistent, constitutive equation for the magnetophoretic flux of magnetic nanoparticles suspended in a medium exposed to a stationary magnetic field. The constitutive relationship accounts for contributions from magnetic diffusion, magnetic convection, residual magnetization, and electromagnetic drift. We discovered that the key physical properties governing the magnetophoresis are magnetic diffusion coefficient, magnetic velocity, and activity coefficient, which depend on relative magnetic energy and the molar magnetic susceptibility of particles. The constitutive equation also reveals previously unknown ballistic and diffusive limits for magnetophoresis wherein the paramagnetic particles either aggregate near the magnet or diffusive away from the magnet, respectively. In the diffusive limit, the particle concentration is linearly proportional to the relative magnetic energy of the suspension of paramagnetic particles. The region of the localization of paramagnetic particles near the magnet decreases with increasing the strength of the magnet. The dynamic accumulation of nanoparticles, measured as the thickness of the nanoparticle aggregate, near the magnet compares well with the theoretical prediction. The effect of convective mixing on the rate of magnetophoresis is also discussed for the magnetic targeting applications.
more » « less- Award ID(s):
- 1706921
- NSF-PAR ID:
- 10202091
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 48
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- p. 30208-30214
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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