Editing Microfluidics (section)

==Microscale behaviour of fluids==
[[File:Microfluidics.jpg|250px|thumb|right|Silicone rubber and glass microfluidic devices. Top: a photograph of the devices. Bottom: [[Phase contrast]] [[micrograph]]s of a serpentine channel ~15 [[μm]] wide.]]
The behaviour of fluids at the microscale can differ from "macrofluidic" behaviour in that factors such as [[surface tension]], energy dissipation, and fluidic resistance start to dominate the system. Microfluidics studies how these behaviours change, and how they can be worked around, or exploited for new uses.<ref>{{cite journal|vauthors = Terry SC, Jerman JH, Angell JB|s2cid = 21971431|title = A gas chromatographic air analyzer fabricated on a silicon wafer.|journal = IEEE Transactions on Electron Devices|date = December 1979|volume = 26|issue = 12|pages = 1880–6|doi = 10.1109/T-ED.1979.19791|bibcode = 1979ITED...26.1880T }}</ref><ref name=Kirby>{{cite book|vauthors=Kirby BJ|title=Micro- and Nanoscale Fluid Mechanics: Transport in Microfluidic Devices|url=http://www.kirbyresearch.com/textbook|year=2010|publisher=[[Cambridge University Press]]|access-date=2010-02-13|archive-date=2019-04-28|archive-url=https://web.archive.org/web/20190428234717/http://www.kirbyresearch.com/textbook/|url-status=dead }}</ref><ref name=Karniadakis>{{cite book|vauthors = Karniadakis GM, Beskok A, Aluru N|title=Microflows and Nanoflows|year=2005|publisher =[[Springer Verlag]] }}</ref><ref name=Bruus>{{cite book|vauthors = Bruus H|title=Theoretical Microfluidics|year=2007|publisher =[[Oxford University Press]] }}</ref><ref>{{cite book|title=Principles of Microfluidics|vauthors = Shkolnikov V|year=2019| publisher=Amazon Digital Services LLC - Kdp |isbn=978-1790217281}}</ref>

At small scales (channel size of around 100 [[nanometers]] to 500 [[micrometers]]) some unintuitive properties appear. In particular, the [[Reynolds number]] (which compares the effect of the momentum of a fluid to the effect of [[viscosity]]) can become very low. One consequence is co-flowing fluids do not necessarily mix in the traditional sense, as flow becomes [[laminar flow|laminar]] rather than [[turbulent flow|turbulent]]; molecular transport between them must often be through [[diffusion]].<ref name=Tabeling>{{cite book|vauthors = Tabeling P|title=Introduction to Microfluidics|url=https://archive.org/details/introductiontomi0000tabe|url-access=registration|year=2005|publisher =[[Oxford University Press]] |isbn=978-0-19-856864-3}}</ref>

High specificity of chemical and physical properties (concentration, pH, temperature, shear force, etc.) can also be ensured resulting in more uniform reaction conditions and higher grade products in single and multi-step reactions.<ref name="microreactors">{{cite journal | vauthors = Chokkalingam V, Weidenhof B, Krämer M, Maier WF, Herminghaus S, Seemann R | title = Optimized droplet-based microfluidics scheme for sol-gel reactions | journal = Lab on a Chip | volume = 10 | issue = 13 | pages = 1700–1705 | date = July 2010 | pmid = 20405061 | doi = 10.1039/b926976b }}</ref><ref name="microfluidic reactions">{{cite journal |vauthors=Shestopalov I, Tice JD, Ismagilov RF |date=August 2004 |title=Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system |url=https://web.archive.org/web/20221022174003/https://authors.library.caltech.edu/40869/ |journal=Lab on a Chip |volume=4 |issue=4 |pages=316–321 |doi=10.1039/b403378g |pmid=15269797}}<!--https://authors.library.caltech.edu/40869/1/Ismagilov_LOC_2004_4_316_Shestopalov_Mulitstep_synthesis_nanoparticles_ms_timescale_ufl_droplet_system.pdf }}--></ref>