Editing Van der Waals force (section)

==Use by geckos and arthropods==
{{further|Arthropod adhesion}}
[[File:Gecko Leaftail 1.jpg|thumb|[[Gecko]] climbing a glass surface]]

The ability of [[gecko]]s – which can hang on a glass surface using only one toe – to climb on sheer surfaces has been for many years mainly attributed to the van der Waals forces between these surfaces and the [[Spatulae (biology)|spatulae]], or microscopic projections, which cover the hair-like [[seta]]e found on their footpads.<ref name="RussellHigham2009">{{Cite journal |last1=Russell |first1=Anthony P. |last2=Higham |first2=Timothy. E. |date=2009 |title=A new angle on clinging in geckos: incline, not substrate, triggers the deployment of the adhesive system |journal=Proceedings of the Royal Society B: Biological Sciences |volume=276 |issue=1673 |pages=3705–3709 |doi=10.1098/rspb.2009.0946 |issn=0962-8452 |pmc=2817305 |pmid=19656797}}</ref><ref>{{Cite journal |last1=Autumn |first1=Kellar |last2=Sitti |first2=Metin |last3=Liang |first3=Yiching A. |last4=Peattie |first4=Anne M. |last5=Hansen |first5=Wendy R. |last6=Sponberg |first6=Simon |last7=Kenny |first7=Thomas W. |last8=Fearing |first8=Ronald |last9=Israelachvili |first9=Jacob N. |year=2002 |title=Evidence for van der Waals adhesion in gecko setae |journal=Proceedings of the National Academy of Sciences |volume=99 |issue=19 |pages=12252–6 |bibcode=2002PNAS...9912252A |doi=10.1073/pnas.192252799 |pmc=129431 |pmid=12198184 |first10=Robert J. |last10=Full|doi-access=free }}</ref> 

There were efforts in 2008 to create a [[dry glue]] that exploits the effect,<ref>{{Cite news |last=Steenhuysen |first=Julie |date=8 October 2008 |title=Gecko-like glue is said to be stickiest yet |work=[[Reuters]] |url=https://www.reuters.com/article/us-nano-glue-idUSN0942431020081009 |access-date=5 October 2016}}</ref> and success was achieved in 2011 to create an adhesive tape on similar grounds<ref>{{Cite web |last=Quick |first=Darren |date=6 November 2011 |title=Biologically inspired adhesive tape can be reused thousands of times |url=http://newatlas.com/bioinspired-adhesive-tape-kiel/20406/ |access-date=5 October 2016 |website=New Atlas}}</ref> (i.e. based on van der Waals forces). In 2011, a paper was published relating the effect to both velcro-like hairs and the presence of lipids in gecko footprints.<ref name="HsuGe20112">{{Cite journal |last1=Hsu |first1=Ping Yuan |last2=Ge |first2=Liehui |last3=Li |first3=Xiaopeng |last4=Stark |first4=Alyssa Y. |last5=Wesdemiotis |first5=Chrys |last6=Niewiarowski |first6=Peter H. |last7=Dhinojwala |first7=Ali |date=24 August 2011 |title=Direct evidence of phospholipids in gecko footprints and spatula-substrate contact interface detected using surface-sensitive spectroscopy |journal=[[Journal of the Royal Society Interface]] |volume=9 |issue=69 |pages=657–664 |doi=10.1098/rsif.2011.0370 |issn=1742-5689 |pmc=3284128 |pmid=21865250}}</ref>

A later study suggested that capillary adhesion might play a role,<ref>{{Cite journal |last1=Huber |first1=Gerrit |last2=Mantz |first2=Hubert |last3=Spolenak |first3=Ralph |last4=Mecke |first4=Klaus |last5=Jacobs |first5=Karin |last6=Gorb |first6=Stanislav N. |last7=Arzt |first7=Eduard |date=2005 |title=Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements |journal=Proceedings of the National Academy of Sciences |volume=102 |issue=45 |pages=16293–16296 |bibcode=2005PNAS..10216293H |doi=10.1073/pnas.0506328102 |pmc=1283435 |pmid=16260737 |doi-access=free}}</ref> but that hypothesis has been rejected by more recent studies.<ref>{{Cite journal |last1=Chen |first1=Bin |last2=Gao |first2=Huajian |date=2010 |title=An alternative explanation of the effect of humidity in gecko adhesion: stiffness reduction enhances adhesion on a rough surface |journal=International Journal of Applied Mechanics |volume=2 |issue=1 |pages=1–9 |bibcode=2010IJAM....2....1C |doi=10.1142/s1758825110000433}}</ref><ref>{{Cite journal |last1=Puthoff |first1=Jonathan B. |last2=Prowse |first2=Michael S. |last3=Wilkinson |first3=Matt |last4=Autumn |first4=Kellar |year=2010 |title=Changes in materials properties explain the effects of humidity on gecko adhesion |journal=Journal of Experimental Biology |volume=213 |issue=21 |pages=3699–3704 |doi=10.1242/jeb.047654 |pmid=20952618 |doi-access=free|bibcode=2010JExpB.213.3699P }}</ref><ref>{{Cite journal |last1=Prowse |first1=Michael S. |last2=Wilkinson |first2=Matt |last3=Puthoff |first3=Michael |last4=Mayer |first4=George |last5=Autumn |first5=Kellar |date=February 2011 |title=Effects of humidity on the mechanical properties of gecko setae |journal=[[Acta Biomaterialia]] |volume=7 |issue=2 |pages=733–738 |doi=10.1016/j.actbio.2010.09.036 |pmid=20920615}}</ref>

A 2014 study has shown that gecko adhesion to smooth Teflon and [[polydimethylsiloxane]] surfaces is mainly determined by electrostatic interaction (caused by [[contact electrification]]), not van der Waals or capillary forces.<ref>{{cite journal |last1=Izadi|first1=H.|last2=Stewart|first2=K. M. E.|last3=Penlidis|first3=A.|title=Role of contact electrification and electrostatic interactions in gecko adhesion |journal=Journal of the Royal Society Interface |date=9 July 2014 |volume=11 |issue=98 |pages=20140371 |doi=10.1098/rsif.2014.0371|pmid=25008078|pmc=4233685|quote=We have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.}}</ref>

Among the [[arthropod]]s, some spiders have similar setae on their [[scopulae]] or scopula pads, enabling them to climb or hang upside-down from extremely smooth surfaces such as glass or porcelain.<ref name="KeselMartin2004">{{Cite journal |last1=Kesel |first1=Antonia B. |last2=Martin |first2=Andrew |last3=Seidl |first3=Tobias |date=19 April 2004 |title=Getting a grip on spider attachment: an AFM approach to microstructure adhesion in arthropods |journal=[[Smart Materials and Structures]] |volume=13 |issue=3 |pages=512–518 |doi=10.1088/0964-1726/13/3/009 |issn=0964-1726|bibcode=2004SMaS...13..512K |s2cid=250841250 }}</ref><ref>{{Cite journal |last1=Wolff |first1=Jonas O. |last2=Gorb |first2=Stanislav N. |date=7 January 2012 |title=The influence of humidity on the attachment ability of the spider ''Philodromus dispar'' (Araneae, Philodromidae) |journal=[[Proceedings of the Royal Society B]] |volume=279 |issue=1726 |pages=139–143 |doi=10.1098/rspb.2011.0505 |pmid=21593034 |pmc=3223641 }}</ref>