Editing Microfluidics (section)

=== Microfluidic-assisted magnetophoresis ===
One application for microfluidic devices is the separation and sorting of different fluids or cell types. Microfluidic devices have been integrated with [[wiktionary:magnetophoresis|magnetophoresis]]: the migration of particles by a [[magnetic field]].<ref>{{cite journal | vauthors = Munaz A, Shiddiky MJ, Nguyen NT | title = Recent advances and current challenges in magnetophoresis based micro magnetofluidics | journal = Biomicrofluidics | volume = 12 | issue = 3 | pages = 031501 | date = May 2018 | pmid = 29983837 | pmc = 6013300 | doi = 10.1063/1.5035388 }}</ref> This can be accomplished by sending a fluid containing at least one magnetic component through a microfluidic channel that has a [[magnet]] positioned along the length of the channel. This creates a magnetic field inside the microfluidic channel which draws [[Magnetism|magnetically]] active substances towards it, effectively separating the magnetic and non-magnetic components of the fluid. This technique can be readily utilized in [[Industry (manufacturing)|industrial]] settings where the fluid at hand already contains magnetically active material. For example, a handful of [[Metal|metallic impurities]] can find their way into certain consumable liquids, namely [[milk]] and other [[dairy]] products.<ref name="sciencedirect.com">{{cite journal| vauthors = Dibaji S, Rezai P |date=2020-06-01|title=Triplex Inertia-Magneto-Elastic (TIME) sorting of microparticles in non-Newtonian fluids |journal=Journal of Magnetism and Magnetic Materials|language=en|volume=503|pages=166620|doi=10.1016/j.jmmm.2020.166620|bibcode=2020JMMM..50366620D|s2cid=213233645|issn=0304-8853}}</ref> Conveniently, in the case of milk, many of these metal contaminants exhibit [[paramagnetism]]. Therefore, before packaging, milk can be flowed through channels with magnetic gradients as a means of purifying out the metal contaminants.

[[Cell (biology)|cell]] separations are of interest in microfluidics. This is accomplished. First, a paramagnetic substance (usually micro/[[nanoparticle]]s or a [[Ferrofluid|paramagnetic fluid]])<ref>{{cite journal | vauthors = Alnaimat F, Dagher S, Mathew B, Hilal-Alnqbi A, Khashan S | title = Microfluidics Based Magnetophoresis: A Review | journal = Chemical Record | volume = 18 | issue = 11 | pages = 1596–1612 | date = November 2018 | pmid = 29888856 | doi = 10.1002/tcr.201800018 | s2cid = 47016122 }}</ref> needs to be [[Functional group|functionalized]] to target the cell type of interest. This can be accomplished by identifying a [[Membrane protein|transmembranal protein]] unique to the cell type of interest and subsequently functionalizing magnetic particles with the complementary [[antigen]] or [[antibody]].<ref name="sciencedirect.com"/><ref>{{cite journal | vauthors = Unni M, Zhang J, George TJ, Segal MS, Fan ZH, Rinaldi C | title = Engineering magnetic nanoparticles and their integration with microfluidics for cell isolation | journal = Journal of Colloid and Interface Science | volume = 564 | pages = 204–215 | date = March 2020 | pmid = 31911225 | pmc = 7023483 | doi = 10.1016/j.jcis.2019.12.092 | bibcode = 2020JCIS..564..204U }}</ref><ref>{{cite journal | vauthors = Xia N, Hunt TP, Mayers BT, Alsberg E, Whitesides GM, Westervelt RM, Ingber DE | title = Combined microfluidic-micromagnetic separation of living cells in continuous flow | journal = Biomedical Microdevices | volume = 8 | issue = 4 | pages = 299–308 | date = December 2006 | pmid = 17003962 | doi = 10.1007/s10544-006-0033-0 | s2cid = 14534776 }}</ref><ref name="Magnetism and microfluidics">{{cite journal | vauthors = Pamme N | title = Magnetism and microfluidics | journal = Lab on a Chip | volume = 6 | issue = 1 | pages = 24–38 | date = January 2006 | pmid = 16372066 | doi = 10.1039/B513005K }}</ref><ref>{{cite journal | vauthors = Song K, Li G, Zu X, Du Z, Liu L, Hu Z | title = The Fabrication and Application Mechanism of Microfluidic Systems for High Throughput Biomedical Screening: A Review | journal = Micromachines | volume = 11 | issue = 3 | pages = 297 | date = March 2020 | pmid = 32168977 | pmc = 7143183 | doi = 10.3390/mi11030297 | doi-access = free }}</ref> Once the magnetic particles are functionalized, they are dispersed in a cell mixture where they bind to only the cells of interest. The resulting cell/particle mixture can then be flowed through a microfluidic device with a magnetic field to separate the targeted cells from the rest.

Conversely, microfluidic-assisted magnetophoresis may be used to facilitate efficient mixing within microdroplets or plugs. To accomplish this, microdroplets are injected with paramagnetic nanoparticles and are flowed through a straight channel which passes through rapidly alternating magnetic fields. This causes the magnetic particles to be quickly pushed from side to side within the droplet and results in the mixing of the microdroplet contents.<ref name="Magnetism and microfluidics"/> This eliminates the need for tedious engineering considerations that are necessary for traditional, channel-based droplet mixing. Other research has also shown that the label-free separation of cells may be possible by suspending cells in a paramagnetic fluid and taking advantage of the magneto-Archimedes effect.<ref>{{cite journal| vauthors = Gao QH, Zhang WM, Zou HX, Li WB, Yan H, Peng ZK, Meng G |date=2019|title=Label-free manipulation via the magneto-Archimedes effect: fundamentals, methodology and applications|url=http://xlink.rsc.org/?DOI=C8MH01616J|journal=Materials Horizons |volume=6 |issue=7 |pages=1359–1379 |doi=10.1039/C8MH01616J|s2cid=133309954|issn=2051-6347}}</ref><ref>{{cite journal| vauthors = Akiyama Y, Morishima K |date=2011-04-18|title=Label-free cell aggregate formation based on the magneto-Archimedes effect|journal=Applied Physics Letters|volume=98|issue=16|pages=163702|doi=10.1063/1.3581883|bibcode=2011ApPhL..98p3702A|issn=0003-6951}}</ref> While this does eliminate the complexity of particle functionalization, more research is needed to fully understand the magneto-Archimedes phenomenon and how it can be used to this end. This is not an exhaustive list of the various applications of microfluidic-assisted magnetophoresis; the above examples merely highlight the versatility of this [[Separation process|separation technique]] in both current and future applications.