Gecko adhesion: An evolutionary approach
Tokay and house geckos with lead weights used to study climbing. Photo by M. Ramos
The ability of geckos to climb walls is one of the most remarkable feats in nature. In the first study that showed the power of these toepads, Irschick et al. (1996) revealed that the two front feet could hold up to 20 N for a large tokay gecko, which is equivalent to a bag of 20 apples. This amazing force is produced purely by dry adhesion. The feet of geckos is complex, and they possess microscopic hairs (setae) that allow them, along with other structures in their feet to produce these dry adhesive forces. As an example of his work, Duncan Irschick and has recently collaborated with Al Crosby from the Polymer Sciences Dept at the University of Massachusetts at Amherst to apply evolutionary and anatomical principles towards the creation of a novel gecko-like adhesive. In February of 2012, they, along with Mike Bartlett, Dan King, and others, published a paper in the journal Advanced Materials that described GeckskinTM, a synthetic adhesive that mimics gecko feet. GeckskinTM is capable of holding more than 700 lbs (300 kg) on smooth surfaces (e.g., glass), yet is easily removable, and leaves no residue. GeckskinTM has been hailed as a breakthrough because of its ability to provide powerful, removable and reusable adhesion at large sizes.
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Vanhooydonck B, Andronescu A*, Herrel, A, and Irschick DJ. 2005. Effects of substrate structure on speed and acceleration capacity in climbing geckos. Biological Journal of the Linnean Society. 85:385-393.
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Bergmann P, Irschick DJ. 2006. Effects of temperature on maximum acceleration, deceleration and power output during vertical running in geckos. Journal of Experimental Biology. 209:1404-1412
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Irschick DJ, Herrel A, VanHooydonck B. 2006. Whole-organism studies of adhesion in pad-bearing lizards: Creative evolutionary solutions to functional problems. Journal of Comparative Physiology A. 192:1169-1177.
VanHooydonck B, Herrel A, Van Damme R, Irschick DJ. 2006. The quick and the fast: the evolution of acceleration capacity in Anolis lizards. Evolution. 60:2137–2147.
VanHooydonck B, Herrel A, Irschick DJ. 2006. Out on a limb: the differential effect of substrate diameter on acceleration capacity in Anolis lizards. Journal of Experimental Biology. 209: 4515-4523.
Bartlett M, Croll AB, King DR, Irschick DJ*, Crosby AJ. 2012. Looking Beyond Fibrillar Features to Scale Gecko-Like Adhesion. Advanced Materials (IF=13.9, Cover). 24:1078-1083 (*Irschick co-corresponding author) (Featured in The Daily Mail, Wired Magazine, SmartPlanet.com, The New Zealand Herald, New Scientist.com, NPR, Yahoo!, Voice of America, The Daily Planet, CNET.com, WTOP Radio, Daily KOS, Campbell Biology textbook, 10th Edition, and many other outlets)
Click here for access to a rather large (~30 mb) gecko movie (running uphill with a large load on it)