Editing Ferrofluid (section)

===Future===
====Spacecraft propulsion====
{{further|Spacecraft propulsion}}
Ferrofluids can be made to self-assemble nanometer-scale needle-like sharp tips under the influence of a magnetic field. When they reach a critical thinness, the needles begin emitting jets that might be used in the future as a thruster mechanism to propel small satellites such as [[CubeSat]]s.<ref>{{Cite news|url=http://www.spacesafetymagazine.com/2013/10/17/novel-thrusters-developed-nanosats|title=Novel Thrusters Being Developed for Nanosats|date=2013-10-17|work=Space Safety Magazine|access-date=2018-07-09|language=en-US|last=Raval |first=Siddharth }}</ref>

====Analytical instrumentation====
Ferrofluids have numerous [[optical]] applications because of their [[refractive]] properties; that is, each grain, a [[magnet|micromagnet]], reflects light. These applications include measuring [[specific viscosity]] of a liquid placed between a [[polarizer]] and an [[analyzer]], illuminated by a [[helium–neon laser]].<ref>{{cite journal|doi=10.1016/j.proeng.2013.09.250|title=Transient Optical Phenomenon in Ferrofluids|journal=Procedia Engineering|volume=76|pages=74–79|year=2014|last1=Pai|first1=Chintamani|last2=Shalini|first2=M|last3=Radha|first3=S|doi-access=free}}</ref>

====Medical applications====
Ferrofluids have been proposed for magnetic drug targeting. In this process the drugs would be attached to or enclosed within a ferrofluid and could be targeted and selectively released using magnetic fields.<ref>{{cite journal|last1=Kumar|first1=CS|last2=Mohammad|first2=F|title=Magnetic nanomaterials for hyperthermia-based therapy and controlled drug delivery|journal=Advanced Drug Delivery Reviews|date=14 August 2011|volume=63|issue=9|pages=789–808|pmid=21447363|pmc=3138885|doi=10.1016/j.addr.2011.03.008}}</ref>

It has also been proposed for targeted [[magnetic hyperthermia]] to convert electromagnetic energy into heat.<ref>{{cite journal|last1=Kafrouni|first1=L|last2=Savadogo|first2=O|title=Recent progress on magnetic nanoparticles for magnetic hyperthermia|journal=Progress in Biomaterials|date=December 2016|volume=5|issue=3–4|pages=147–160|doi=10.1007/s40204-016-0054-6|pmid=27995583|pmc=5304434}}</ref>

It has also been proposed in a form of nanosurgery to separate one tissue from another—for example a tumor from the tissue in which it has grown.<ref name=app>{{cite journal|author1=Scherer, C.  |author2=Figueiredo Neto, A. M. |title=Ferrofluids: Properties and Applications|journal= Brazilian Journal of Physics|volume=35|issue=3A|pages=718–727|date=2005|url=http://www.sbfisica.org.br/bjp/files/v35_718.pdf|doi=10.1590/S0103-97332005000400018|bibcode = 2005BrJPh..35..718S |doi-access=free}}</ref>

====Heat transfer====
An external magnetic field imposed on a ferrofluid with varying susceptibility (e.g., because of a temperature gradient) results in a nonuniform magnetic body force, which leads to a form of [[heat transfer]] called [[thermomagnetic convection]].  This form of heat transfer can be useful when conventional convection heat transfer is inadequate; e.g., in miniature microscale devices or under [[microgravity|reduced gravity]] conditions.

Ferrofluids of suitable composition can exhibit extremely large enhancement in thermal conductivity (k; ~300% of the base fluid thermal conductivity). The large enhancement in k is due to the efficient transport of heat through percolating nanoparticle paths. Special magnetic [[nanofluid]]s with tunable thermal conductivity to viscosity ratio can be used as multifunctional ‘smart materials’ that can remove heat and also arrest vibrations (damper). Such fluids may find applications in microfluidic devices and microelectromechanical systems ([[MEMS]]).<ref>{{cite journal|doi=10.1021/jp204827q |title=Tuning of Thermal Conductivity and Rheology of Nanofluids Using an External Stimulus|date=2011|last1=Shima|first1=P. D.|last2=Philip|first2=John|journal=The Journal of Physical Chemistry C|volume=115|issue=41|page=20097}}</ref>

====Optics====
Research is under way to create an [[Ferrofluid mirror|adaptive optics shape-shifting magnetic mirror]] from ferrofluid for Earth-based astronomical [[Optical telescope|telescope]]s.<ref>{{cite news|publisher=New Scientist|title=Morphing mirror could clear the skies for astronomers|date=7 November 2008|author=Hecht, Jeff |url=https://www.newscientist.com/article/dn15154-morphing-mirror-could-clear-the-skies-for-astronomers.html}}</ref>

Optical filters are used to select different wavelengths of light. The replacement of filters is cumbersome, especially when the wavelength is changed continuously with tunable-type lasers. Optical filters tunable for different wavelengths by varying the magnetic field can be built using ferrofluid emulsion.<ref>{{cite journal|doi=10.1088/0957-0233/14/8/314|title=A tunable optical filter|date=2003|last1=Philip|first1=John|last2=Jaykumar|first2=T|last3=Kalyanasundaram|first3=P|last4=Raj|first4=Baldev|journal=Measurement Science and Technology|volume=14|issue=8|page=1289|bibcode = 2003MeScT..14.1289P |s2cid=250923543 }}</ref>

====Energy harvesting====
Ferrofluids enable the harvesting of vibration energy from the environment. Existing methods of harvesting low frequency (<100&nbsp;Hz) vibrations require the use of solid resonant structures. With ferrofluids, energy harvester designs no longer need solid structure. One example of ferrofluid based [[energy harvesting]] is to place the ferrofluid inside a container to use external mechanical vibrations to generate electricity inside a coil wrapped around the container surrounded by a permanent magnet.<ref name="Bibo2012">{{cite journal|last1=Bibo|first1=A.|last2=Masana|first2=R.|last3=King|first3=A.|last4=Li|first4=G.|last5=Daqaq|first5=M.F.|title=Electromagnetic ferrofluid-based energy harvester|journal=Physics Letters A|date=June 2012|volume=376|issue=32|pages=2163–2166|doi=10.1016/j.physleta.2012.05.033|bibcode=2012PhLA..376.2163B}}</ref> First a ferrofluid is placed inside a container that is wrapped with a coil of wire. The ferrofluid is then externally magnetized using a permanent magnet. When external vibrations cause the ferrofluid to slosh around in the container, there is a change in magnetic flux fields with respect to the coil of wire. Through [[Faraday's Law of Induction|Faraday's law of electromagnetic induction]], voltage is induced in the coil of wire due to change in magnetic flux.<ref name="Bibo2012"/>