Editing Gel (section)

===Colloidal gels===

A [[colloid]]al gel consists of a [[Percolation theory|percolated]] network of particles in a fluid medium,<ref>{{cite journal | vauthors=((Zaccarelli, E.)) | journal=Journal of Physics: Condensed Matter | title=Colloidal gels: equilibrium and non-equilibrium routes | volume=19 | issue=32 | pages=323101 | date=15 August 2007 |  doi=10.1088/0953-8984/19/32/323101| arxiv=0705.3418 | bibcode=2007JPCM...19F3101Z | s2cid=17294391 }}</ref> providing [[Rheology|mechanical properties]],<ref>{{cite journal | vauthors=((Tsurusawa, H.)), ((Leocmach, M.)), ((Russo, J.)), ((Tanaka, H.)) | journal=Science Advances | title=Direct link between mechanical stability in gels and percolation of isostatic particles | volume=5 | issue=5 | pages=eaav6090 | date= May 2019 | doi=10.1126/sciadv.aav6090| pmid=31172025 | pmc=6544450 | arxiv=1804.04370 | bibcode=2019SciA....5.6090T }}</ref> in particular the emergence of elastic behaviour.<ref>{{cite journal | vauthors=((Whitaker, K.)), ((Varga, Z.)), ((Hsiao, L.)), ((Solomon, M.)), ((Swan, J.)), ((Furst, E.))  | journal=Nature Communications | title=Colloidal gel elasticity arises from the packing of locally glassy clusters | volume= 10 | date= May 2019 | issue=1 | page=2237 | doi=10.1038/s41467-019-10039-w | pmid=31110184 | pmc=6527676 | bibcode=2019NatCo..10.2237W }}</ref> The particles can show attractive interactions through [[Depletion force|osmotic depletion]] or through polymeric links.<ref>{{cite journal | vauthors=((Howard, M. P.)), ((Jadrich, R. B.)), ((Lindquist, B. A.)), ((Khabaz, F.)), ((Bonnecaze, R. T.)), ((Milliron, D. J.)), ((Truskett, T. M.)) | journal=The Journal of Chemical Physics | title=Structure and phase behavior of polymer-linked colloidal gels | volume=151 | issue=12 | pages=124901 | date=28 September 2019 | doi=10.1063/1.5119359| pmid=31575167 | arxiv=1907.04874 | bibcode=2019JChPh.151l4901H | s2cid=195886583 }}
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Colloidal gels have three phases in their lifespan: gelation, aging and collapse.<ref>{{cite journal | vauthors=((Lu, P. J.)), ((Zaccarelli, E.)), ((Ciulla, F.)), ((Schofield, A. B.)), ((Sciortino, F.)), ((Weitz, D. A.)) | journal=Nature | title=Gelation of particles with short-range attraction | volume=453 | issue=7194 | pages=499–503 | date= May 2008 | doi=10.1038/nature06931| pmid=18497820 | bibcode=2008Natur.453..499L | s2cid=4409873 }}</ref><ref>{{cite journal | vauthors=((Zia, R. N.)), ((Landrum, B. J.)), ((Russel, W. B.)) | journal=Journal of Rheology | title=A micro-mechanical study of coarsening and rheology of colloidal gels: Cage building, cage hopping, and Smoluchowski's ratchet | volume=58 | issue=5 | pages=1121–1157 | date= September 2014  | doi=10.1122/1.4892115| bibcode=2014JRheo..58.1121Z }}
</ref> The gel is initially formed by the assembly of particles into a space-spanning network, leading to a phase arrest. In the aging phase, the particles slowly rearrange to form thicker strands, increasing the elasticity of the material. Gels can also be collapsed and separated by external fields such as gravity.<ref>{{cite journal | vauthors=((Manley, S.)), ((Skotheim, J. M.)), ((Mahadevan, L.)), ((Weitz, D. A.)) | journal=Physical Review Letters | title=Gravitational Collapse of Colloidal Gels | volume=94 | issue=21 | pages=218302 | date=3 June 2005 | doi=10.1103/PhysRevLett.94.218302| pmid=16090356 | bibcode=2005PhRvL..94u8302M | s2cid=903595 | url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:41417294 }}</ref> Colloidal gels show linear response rheology at low amplitudes.<ref>{{cite journal | vauthors=((Johnson, L. C.)), ((Zia, R. N.)), ((Moghimi, E.)), ((Petekidis, G.)) | journal=Journal of Rheology | title=Influence of structure on the linear response rheology of colloidal gels | volume=63 | issue=4 | pages=583–608 | date= July 2019 | doi=10.1122/1.5082796| bibcode=2019JRheo..63..583J | s2cid=189985243 | doi-access= }}</ref> These materials have been explored as candidates for a drug release matrix.<ref>{{cite journal | vauthors=((Meidia, H.)), ((Irfachsyad, D.)), ((Gunawan, D.)) | journal=IOP Conference Series: Materials Science and Engineering | title=Brownian Dynamics Simulation of Colloidal Gels as Matrix for Controlled Release Application | volume=553 | pages=012011 | date=12 November 2019 | issue=1 | doi=10.1088/1757-899X/553/1/012011| bibcode=2019MS&E..553a2011M | s2cid=210251780 | doi-access=free }}</ref>