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Science 10 October 2008:
Vol. 322. no. 5899, pp. 238 - 242
DOI: 10.1126/science.1159503
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Reports

Carbon Nanotube Arrays with Strong Shear Binding-On and Easy Normal Lifting-Off

Liangti Qu,1 Liming Dai,1* Morley Stone,2 Zhenhai Xia,3 Zhong Lin Wang4*

The ability of gecko lizards to adhere to a vertical solid surface comes from their remarkable feet with aligned microscopic elastic hairs. By using carbon nanotube arrays that are dominated by a straight body segment but with curly entangled top, we have created gecko-foot–mimetic dry adhesives that show macroscopic adhesive forces of ~100 newtons per square centimeter, almost 10 times that of a gecko foot, and a much stronger shear adhesion force than the normal adhesion force, to ensure strong binding along the shear direction and easy lifting in the normal direction. This anisotropic force distribution is due to the shear-induced alignments of the curly segments of the nanotubes. The mimetic adhesives can be alternatively binding-on and lifting-off over various substrates for simulating the walking of a living gecko.

1 Department of Chemical and Materials Engineering, School of Engineering, University of Dayton, 300 College Park, Dayton, OH 45469, USA.
2 Air Force Research Laboratory, Human Effectiveness Directorate, AFRL/RH, Wright-Patterson Air Force Base, OH 45433, USA.
3 Department of Mechanical Engineering, University of Akron, Akron, OH 44325, USA.
4 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.

* To whom correspondence should be addressed. E-mail: ldai{at}udayton.edu (L.D.); zlwang{at}gatech.edu (Z.L.W.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Rate-dependent frictional adhesion in natural and synthetic gecko setae.
N. Gravish, M. Wilkinson, S. Sponberg, A. Parness, N. Esparza, D. Soto, T. Yamaguchi, M. Broide, M. Cutkosky, C. Creton, et al. (2010)
J R Soc Interface 7, 259-269
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A microfabricated wedge-shaped adhesive array displaying gecko-like dynamic adhesion, directionality and long lifetime.
A. Parness, D. Soto, N. Esparza, N. Gravish, M. Wilkinson, K. Autumn, and M. Cutkosky (2009)
J R Soc Interface 6, 1223-1232
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A nontransferring dry adhesive with hierarchical polymer nanohairs.
H. E. Jeong, J.-K. Lee, H. N. Kim, S. H. Moon, and K. Y. Suh (2009)
PNAS 106, 5639-5644
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