Dry glue is a method of adhesion based around the naturally occurring adaptations of the feet of geckos, which allow them to climb sheer surfaces, and even glass walls.
Background
A gecko can hang on a glass surface using only one toe. This ability of geckos has been attributed to Van der Waals force,[1][2] although a more recent study suggests that water molecules of roughly monolayer thickness (present on virtually all natural surfaces) also play a role.[3]
Developments
Efforts continue to create a synthetic "gecko tape" that exploits the gecko's abilities. So far, research has produced some promising results — early research yielded an adhesive tape[4] product, which only obtains a fraction of the forces measured from the natural material, and new research[5] is being developed with the goal of featuring 200 times the adhesive forces of the natural material.
In 2006, researchers at Stanford University and Carnegie Mellon University developed a gecko-like robot which uses synthetic setae to mount walls.[6]
On October 9, 2008, the discovery of a new type of dry glue designed to mimic gecko feet was announced. The glue is 10 times stickier than the gravity-defying lizards, and three times stickier than other gecko-inspired glues. Liming Dai of the University of Dayton said "It's the stickiest dry glue yet".[7]
Military use
DARPA (Defense Advanced Research Projects Agency) is also currently working on this technology to enable a soldier to scale a wall at .5 m/s. This project is named Z-Man. Experiments are currently underway to develop nano-adhesives using the Van der Waals effect. Researchers at Rensselaer Polytechnic Institute and the the University of Akron, in the US, have created a material made of columns of carbon nanotubes rooted in pieces of flexible polymer. The nanotubes were grown on a silicon base and then transferred to the polymer to provide a flexible base, similar to a gecko's foot. When dried, the polymer holds the silicon base, which in turn, holds the nanotubes.
Researchers announced in a paper published in the June 18–22, 2007 issue of the Proceedings of the National Academy of Sciences that using this technique they have created a synthetic “gecko tape” with four times the sticking power of a natural gecko foot.[8] Particularly effective has been a checkerboard carpet of this material, which can be peeled and re-adhered repeatedly without weakening.[9]
References
- ^ http://www.clemson.edu/newsroom/articles/2009/august/geckos.php5
- ^ Kellar Autumn; Metin Sitti ; Yiching A. Liang; Anne M. Peattie; Wendy R. Hansen; Simon Sponberg; Thomas W. Kenny; Ronald Fearing; Jacob N. Israelachvili; Robert J. Full. Evidence for van der Waals adhesion in gecko setae. Proceedings of the National Academy of Sciences of the USA 2002, 99, 12252–12256. doi:10.1073/pnas.192252799
- ^ G. Huber, H. Mantz, R. Spolenak, K. Mecke, K. Jacobs, S. N. Gorb, and E. Arzt. Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements. Proceedings of the National Academy of Sciences of the USA 2005, 102, 16293–16296. doi:10.1073/pnas.0506328102
- ^ Will Knight (2003-06-01), Gecko-like robot scampers up the wall, New Scientist, doi:10.1038/nmat917), archived from the original on 2007-12-13, retrieved 2009-05-02,
Journal reference: Nature Materials (DOI: 10.1038/nmat917)
- ^ Synthetic gecko foot-hairs leading to reusable adhesives, University of Akron press release, 12 August 2005
- ^ Gecko-like robot scampers up the wall, New Scientist, 2006-05-23, p. 29, archived from the original on 2007-12-16, retrieved 2009-05-02
- ^ Gecko-like glue is said to be stickiest yet, "reuters.com" 08 Oct 2008
- ^ Nanotube adhesive sticks better than a gecko's foot, PhysOrg.com retrieved 7 July 2007
- ^ http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=112442&org=NSF