- Synthetic setae
Synthetic setae emulate the
setae found on the toes of agecko and scientific research in this area is driven towards the development ofdry adhesive s. Geckos have no difficulty mastering vertical walls and are apparently capable of adhering themselves to just about any surface. The 5-toed feet of a gecko are covered with elastic hairs calledsetae and the end of these hairs are split into so-called spatulas (no doubt because they carry a resemblance to actualspatula s). The sheer abundance and proximity to the surface of these spatulas make it sufficient forvan der Waals force s alone to provide the required adhesive strength. [ cite web | title = Evidence for van der Waals adhesion in gecko setae | authors = Kellar Autumn,Metin Sitti , Yiching A. Liang, Anne M. Peattie†i, Wendy R. Hansen, Simon Sponberg, Thomas W. Kenny, Ronald Fearing, Jacob N. Israelachvili, and Robert J. Full | publisher = PNAS | date =27 August 2002 | url = http://www.pnas.org/cgi/reprint/192252799v1 ]Approaches
One experimental inroad to artificial setae is provided by
nanotube s. In one particular scheme, a thick layer of nanotubes is embedded in a polymer matrix and the adhesive force is calculated to be 200 times that provided by the gecko hairs. These multi walled nanotubes (MWNT) are generated bychemical vapour deposition withxylene as a carbon source andferrocene as acatalyst and exposure of 10 minutes to 800°C on aquartz orsilicon substrate. The nanotubes have a diameter of 1 to 2 nanometres and a length of 65 micrometres. They are dipped into a solution ofmethyl methacrylate withazobisisobutylonitrile as a catalyst and1-decenethiol as achain transfer agent and polymerized toPMMA at 50 °C for 24 hours. The top is then etched away by immersion with asolvent likeacetone exposing the MWNT hairs. In the final step the artificial skin and hairs are stripped from the silicon or quartz substrate.Scanning probe microscopy provides a means to measure adhesive force. [ cite web | title = Synthetic gecko foot-hairs from multiwalled carbon nanotubes | authors = Betul Yurdumakan, Nachiket R. Raravikar, Pulickel M. Ajayan and Ali Dhinojwala | publisher =Chemical Communications | year = 2005 | edition = (30) | pages = 3799 - 3801 | url = http://www.rsc.org/Publishing/Journals/CC/article.asp?doi=b506047h ]Applications
Researchers at Stanford University have created a robot which uses synthetic setae in order to scale even extremely smooth vertical surfaces just as a gecko would. [ [http://www.newscientisttech.com/channel/tech/mg19025526.500.html Gecko-like robot scampers up the wall - tech - 23 May 2006 - New Scientist Tech ] ] [ [http://www.techtree.com/India/Future_Watch/Carbon_Nanotubes_Make_Superglue_Look_Silly/551-94007-505.html Carbon Nanotubes for gecko adhesive] ]
References
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