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News Release 08-179

As Sticky as a Gecko ... but Ten Times Stronger!

Illustration of a gecko hanging off a ledge holding nine more geckos.

A gecko hangs off a ledge holding nine more geckos, demonstrating the power of a new adhesive.


October 14, 2008

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.

The gecko's amazing ability to stick to surfaces and walk up walls has inspired many researchers to manufacture materials that mimic the special surface of a gecko's foot. The secret behind the gecko's ability to stick so well is a forest of pillars at the micro-/nano-scale on the underside of the gecko's foot. Because there are so many pillars so close together, they are held tightly to the surface the gecko is walking on by a molecular force called the Van der Waals force. This relatively weak force causes uncharged molecules to attract each other.

In an unprecedented feat, Liming Dai, at the University of Dayton, and colleagues report in the October 10th issue of Science successful construction of a gecko-inspired adhesive that is ten times stronger than a gecko, at about 100 newtons per square centimeter.

The researchers constructed their adhesive out of two slightly different layers of multi-walled carbon nanotubes. The lower layer is composed of vertically-aligned carbon nanotubes, while the upper segment--which comes into contact with the surface it is sticking to--is curly, like a mess of spaghetti.

As shown in the figure, the adhesive sticks best when it is pulled down parallel to the surface it is sticking to--this is called shear adhesion. This action arranges the tips of the curly nanotubes so they have maximum contact with the substrate, thereby maximizing the Van der Waals force. Pulling the adhesive off in a motion perpendicular to the substrate is much easier--at this angle the sticking force is ten times weaker.

In this way, the adhesive has strong shear adhesion for firm attachment and relatively weak adhesion for detachment perpendicularly to the substrate. Just like a gecko, the adhesive can stick to a wall when needed, and then lift off easily to take the next step. This breakthrough, supported by the National Science Foundation, will have many technological applications.

--Zina Deretsky, NSF

-NSF-

Media Contacts
Joshua A. Chamot, NSF, (703) 292-7730, email: jchamot@nsf.gov
Shawn Robinson, University of Dayton, (937) 229 3391, email: shawn.robinson@notes.udayton.edu

Program Contacts
Ken P. Chong, NSF, (703) 292-7008, email: kchong@nsf.gov

Principal Investigators
Liming Dai, University of Dayton, (937) 830 9395, email: liming.dai@hotmail.com

The U.S. National Science Foundation propels the nation forward by advancing fundamental research in all fields of science and engineering. NSF supports research and people by providing facilities, instruments and funding to support their ingenuity and sustain the U.S. as a global leader in research and innovation. With a fiscal year 2021 budget of $8.5 billion, NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and institutions. Each year, NSF receives more than 40,000 competitive proposals and makes about 11,000 new awards. Those awards include support for cooperative research with industry, Arctic and Antarctic research and operations, and U.S. participation in international scientific efforts.

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