Credit: © 2008 AAAS

Gecko lizards seem to defy gravity by climbing vertical surfaces. Only recently it was discovered that geckos acquire their sticking ability from microscopic hairs, called setae, on their feet. Now scientists in the United States have made a material with ten times the adhesive strength of gecko feet, by using carbon nanotubes to mimic the setae structure.

The material, developed by Liming Dai at the University of Dayton, Zhong Lin Wang at the Georgia Institute of Technology and colleagues1 comprises over 10 billion carbon nanotubes per square centimetre aligned vertically on a silicon wafer. The nanotubes all have curly, entangled tops that enhance the attractive forces between the nanotubes and the surface.

A tiny patch of the material, 4 mm by 4 mm in size, was stuck to a glass wall and used to support weights of well over a kilogram. The patch retained its adhesive strength even after being attached and detached several times.

Most importantly, the adhesion is much stronger parallel to the surface than when a force is applied perpendicularly. This means the material mimics the gecko's best secret — it can easily be unstuck by pulling away from the surface. This makes it highly promising for applications in robotics or 'Spider-man' technologies.