Editing Hydrophobe (section)

==Research and development==
[[File:A-simple-and-fast-fabrication-of-a-both-self-cleanable-and-deep-UV-antireflective-quartz-1556-276X-7-430-S1.ogv|thumb|Water droplets roll down an inclined hydrophobic surface.]]
[[File:Hydrophoby2.webm|thumb|Water droplets on an artificial hydrophobic surface (left)]]

Dettre and Johnson discovered in 1964 that the superhydrophobic [[lotus effect]] phenomenon was related to rough hydrophobic surfaces, and they developed a theoretical model based on experiments with glass beads coated with paraffin or TFE telomer. The self-cleaning property of superhydrophobic micro-[[nanotechnology|nanostructured]] surfaces was reported in 1977.<ref name=Barthlott1977>{{cite book |first1=Wilhelm |last1=Barthlott |first2=Nesta |last2=Ehler |year=1977 |title=Raster-Elektronenmikroskopie der Epidermis-Oberflächen von Spermatophyten |series=Tropische und subtropische Pflanzenwelt |page=110 |language=de |isbn=978-3-515-02620-8}}</ref> Perfluoroalkyl, perfluoropolyether, and RF plasma -formed superhydrophobic materials were developed, used for [[electrowetting]] and commercialized for bio-medical applications between 1986 and 1995.<ref>{{cite web|title= US Patent 4,911,782|author= J. Brown|url= http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4,911,782.PN.&OS=PN/4,911,782&RS=PN/4,911,782|access-date= 2015-01-13|archive-date= 2018-07-14|archive-url= https://web.archive.org/web/20180714221932/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4,911,782.PN.&OS=PN/4,911,782&RS=PN/4,911,782|url-status= dead}}</ref><ref>{{cite web|title= US Patent 5,200,152|author= J. Brown|url= http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,200,152.PN.&OS=PN/5,200,152&RS=PN/5,200,152|access-date= 2015-01-13|archive-date= 2017-07-27|archive-url= https://web.archive.org/web/20170727230714/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,200,152.PN.&OS=PN/5,200,152&RS=PN/5,200,152|url-status= dead}}</ref><ref>{{cite web|title= Stopped-Flow Cytometer|author= National Science Foundation|url= https://www.nsf.gov/awardsearch/advancedSearchResult?PIFirstName=james&PILastName=brown&PIOrganization=cytonix&PIState=MD&PICountry=US&ExpiredAwards=true&#results}}</ref><ref>{{cite web|title= US Patent 5,853,894|author= J. Brown|url= http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,853,894.PN.&OS=PN/5,853,894&RS=PN/5,853,894|access-date= 2015-01-13|archive-date= 2017-01-22|archive-url= https://web.archive.org/web/20170122184631/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,853,894.PN.&OS=PN/5,853,894&RS=PN/5,853,894|url-status= dead}}</ref> Other technology and applications have emerged since the mid-1990s.<ref name=Barthlott1997>{{cite journal |last= Barthlott|first= Wilhelm|author2=C. Neinhuis |year= 1997|title= The purity of sacred lotus or escape from contamination in biological surfaces|journal= [[Planta (journal)|Planta]] |volume= 202|issue= 1|pages= 1–8 |doi= 10.1007/s004250050096|bibcode= 1997Plant.202....1B|s2cid= 37872229}}</ref> A durable superhydrophobic hierarchical composition, applied in one or two steps, was disclosed in 2002 comprising nano-sized particles ≤ 100 nanometers overlaying a surface having micrometer-sized features or particles ≤&nbsp;100 micrometers. The larger particles were observed to protect the smaller particles from mechanical abrasion.<ref>{{cite web|title= US Patent 6,767,587|author= J. Brown|url= http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,767,587.PN.&OS=PN/6,767,587&RS=PN/6,767,587|access-date= 2015-01-13|archive-date= 2018-07-14|archive-url= https://web.archive.org/web/20180714221921/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6,767,587.PN.&OS=PN/6,767,587&RS=PN/6,767,587|url-status= dead}}</ref>

In recent research, superhydrophobicity has been reported by allowing alkylketene [[dimer (chemistry)|dimer]] (AKD) to solidify into a nanostructured fractal surface.<ref>{{cite journal |vauthors= Onda T, Shibuichi S, Satoh N, Tsujii K |title= Super-Water-Repellent Fractal Surfaces |journal=Langmuir |volume=12 |pages=2125–2127 |year=1996 |doi=10.1021/la950418o |issue=9}}</ref> Many papers have since presented fabrication methods for producing superhydrophobic surfaces including particle deposition,<ref name= "Miwa_2000">{{cite journal |vauthors= Miwa M, Nakajima A, Fujishima A, Hashimoto K, Watanabe T |title= Effects of the Surface Roughness on Sliding Angles of Water Droplets on Superhydrophobic Surfaces |journal=Langmuir |volume=16 |pages=5754–60 |year=2000 |doi=10.1021/la991660o |issue=13|s2cid= 97974935 }}</ref> sol-gel techniques,<ref>{{cite journal |vauthors= Shirtcliffe NJ, McHale G, Newton MI, Perry CC |title= Intrinsically superhydrophobic organosilica sol-gel foams |journal=Langmuir |volume=19 |pages=5626–5631 |year=2003 |doi=10.1021/la034204f |issue=14}}</ref> plasma treatments,<ref name="TeareSpanos2002">{{cite journal|last1=Teare|first1=D. O. H.|last2=Spanos|first2=C. G.|last3=Ridley|first3=P.|last4=Kinmond|first4=E. J.|last5=Roucoules|first5=V.|last6=Badyal|first6=J. P. S.|author-link6=Jas Pal Badyal|last7=Brewer|first7=S. A.|last8=Coulson|first8=S.|last9=Willis|first9=C.|title=Pulsed Plasma Deposition of Super-Hydrophobic Nanospheres|journal=Chemistry of Materials|volume=14|issue=11|year=2002|pages=4566–4571|issn=0897-4756|doi=10.1021/cm011600f}}</ref> vapor deposition,<ref name= "Miwa_2000"/> and casting techniques.<ref>{{cite journal |vauthors= Bico J, Marzolin C, Quéré D |title= Pearl drops |journal=[[Europhysics Letters]] |volume=47 |pages=743–744 |year=1999 |doi=10.1209/epl/i1999-00453-y |issue=6 |bibcode=1999EL.....47..743B|doi-access=free }}</ref> Current opportunity for research impact lies mainly in fundamental research and practical manufacturing.<ref>{{cite journal |vauthors= Extrand C |title= Self-Cleaning Surfaces:An Industrial Perspective |journal= MRS Bulletin |pages=733 |year=2008}}</ref> Debates have recently emerged concerning the applicability of the Wenzel and Cassie–Baxter models. In an experiment designed to challenge the surface energy perspective of the Wenzel and Cassie–Baxter model and promote a contact line perspective, water drops were placed on a smooth hydrophobic spot in a rough hydrophobic field, a rough hydrophobic spot in a smooth hydrophobic field, and a hydrophilic spot in a hydrophobic field.<ref>{{cite journal |vauthors= Gao L, McCarthy TJ |title= How Wenzel and Cassie Were Wrong |journal= Langmuir |volume= 23 |issue= 7 |pages= 3762–3765 |year= 2007 |pmid= 17315893 |doi= 10.1021/la062634a|s2cid= 23260001 }}</ref> Experiments showed that the surface chemistry and geometry at the contact line affected the contact angle and [[Contact angle#Contact Angle Hysteresis|contact angle hysteresis]], but the surface area inside the contact line had no effect. An argument that increased jaggedness in the contact line enhances droplet mobility has also been proposed.<ref>{{cite journal |vauthors= Chen W, Fadeev AY, Hsieh ME, Öner D, Youngblood J, McCarthy TJ |title= Ultrahydrophobic and ultralyophobic surfaces: Some comments and examples |journal=Langmuir |volume=15 |pages=3395–3399 |year=1999 |doi=10.1021/la990074s |issue=10}}</ref>

Many hydrophobic materials found in nature rely on [[Cassie's law]] and are [[phase (matter)|biphasic]] on the submicrometer level with one component air. The lotus effect is based on this principle. [[Biomimetics|Inspired by it]], many functional superhydrophobic surfaces have been prepared.<ref>{{cite book |doi= 10.1142/9789812772374_0013 |isbn= 978-981-270-564-8|chapter= Recent Progress on Bio-Inspired Surface with Special Wettability|title= Annual Review of Nano Research|date= 2006|last1= Wang|first1= Shutao|last2= Liu|first2= Huan|last3= Jiang|first3= Lei|volume= 1|pages= 573–628}}</ref>

An example of a [[bionics|bionic]] or [[biomimetics|biomimetic]] superhydrophobic material in [[nanotechnology]] is [[nanopin film]].{{Citation needed|date=January 2021}}

One study presents a [[vanadium pentoxide]] surface that switches reversibly between superhydrophobicity and [[superhydrophilicity]] under the influence of UV radiation.<ref>{{cite journal | last1 = Sun Lim | first1 = Ho | last2 = Kwak | first2 = Donghoon | last3 = Yun Lee | first3 = Dong | last4 = Goo Lee | first4 = Seung | last5 = Cho | first5 = Kilwon | year = 2007 | title = UV-Driven Reversible Switching of a Roselike Vanadium Oxide Film between Superhydrophobicity and Superhydrophilicity | journal = [[J. Am. Chem. Soc.]] | volume = 129 | issue = 14| pages = 4128–4129 | doi = 10.1021/ja0692579 | pmid = 17358065 | bibcode = 2007JAChS.129.4128L }}</ref> According to the study, any surface can be modified to this effect by application of a [[suspension (chemistry)|suspension]] of rose-like V<sub>2</sub>O<sub>5</sub> particles, for instance with an [[inkjet printer]]. Once again hydrophobicity is induced by interlaminar air pockets (separated by 2.1 [[nanometer|nm]] distances). The UV effect is also explained. UV light creates [[electron-hole pair]]s, with the holes reacting with lattice oxygen, creating surface oxygen vacancies, while the electrons reduce V<sup>5+</sup> to V<sup>3+</sup>. The oxygen vacancies are met by water, and it is this water absorbency by the vanadium surface that makes it hydrophilic. By extended storage in the dark, water is replaced by oxygen and [[hydrophilicity]] is once again lost.{{Citation needed|date=January 2021}}

A significant majority of hydrophobic surfaces have their hydrophobic properties imparted by structural or chemical modification of a surface of a bulk material, through either coatings or surface treatments. That is to say, the presence of molecular species (usually organic) or structural features results in high contact angles of water. In recent years, [[Rare-earth element|rare earth]] oxides have been shown to possess intrinsic hydrophobicity.<ref>[http://www.tribonet.org/rare-earth-oxides-make-water-repellent-surfaces-that-last/  Tribonet: Rare earth oxides make water repellent surfaces that last]</ref> The intrinsic hydrophobicity of rare earth oxides depends on surface orientation and oxygen vacancy levels, and is naturally more robust than coatings or surface treatments, having potential applications in condensers and catalysts that can operate at high temperatures or corrosive environments.<ref>{{cite journal | last1=Fronzi| first1=M  | title= Theoretical insights into the hydrophobicity of low index CeO2 surfaces | journal= Applied Surface Science | year=2019 | volume=478 | pages=68–74| doi= 10.1016/j.apsusc.2019.01.208 | arxiv=1902.02662 | bibcode=2019ApSS..478...68F | s2cid=118895100 }}</ref>