Abstract
Magnetic field-induced particle manipulation is simple and economic as compared to other techniques (e.g., electric, acoustic, and optical) for lab-on-a-chip applications. However, traditional magnetic controls require the particles to be manipulated being magnetizable, which renders it necessary to magnetically label particles that are almost exclusively diamagnetic in nature. In the past decade, magnetic fluids including paramagnetic solutions and ferrofluids have been increasingly used in microfluidic devices to implement label-free manipulations of various types of particles (both synthetic and biological). We review herein the recent advances in this field with focus upon the continuous-flow particle manipulations. Specifically, we review the reported studies on the negative magnetophoresis-induced deflection, focusing, enrichment, separation, and medium exchange of diamagnetic particles in the continuous flow of magnetic fluids through microchannels.
Highlights
Lab-on-a-chip devices have been proven to be very useful in handling various types of samples for a wide range of chemical, environmental, and biomedical applications [1,2,3,4]
We present below the published papers on diamagnetic particle deflection in the flow of magnetic fluids under an externally imposed non-uniform (Section 3.1) or uniform (Section 3.2) magnetic field
We briefly present below the studies on diamagnetic particle enrichment in magnetic fluids under the magnetic field of either a pair of magnets (Section 5.1) or a single magnet (Section 5.2)
Summary
Lab-on-a-chip devices have been proven to be very useful in handling various types of samples for a wide range of chemical, environmental, and biomedical applications [1,2,3,4] In these microfluidic systems, many different forces have been demonstrated to control the motion of particles (a general term for any micro/nano-sized small objects that may cover polystyrene (PS) beads, water- or oil-based droplets, bacteria, fungi, mammalian cells, etc.), among which electric [5], magnetic [6], acoustic [7], and optical [8] fields are the most often used. Traditional magnetic techniques require the particles to be manipulated being magnetizable [15,16,17], which renders the magnetic labeling necessary, since majority of the particles (except red blood cells [18] and magnetotactic bacteria [19]) are diamagnetic in nature. We first present a brief overview of the status for both magnetic particles and magnetic fluids
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