Gecko-inspired glue

Geckos are able to climb walls thanks to a coating on their toes of tiny hairs, called "setae," that are tipped with flat "spatulae." The large surface area of the spatulae exploit the van der Waals force, the weak attractive force between molecules, enabling the gecko's feet to stick. For years, scientists have worked on the development of synthetic adhesives inspired by this wonder of nature. Researchers at the University of Dayton and the Georgia Institute of Technology have now made an array of artificial setae that are actually nested carbon nanotubes. Eventually, the resarchers think the material could replace solder as well as more traditional adhesives. From New Scientist:

(The researchers) controlled the (carbon nanotube) growth process to make a forest of vertical nanotube trunks turning into a canopy of tangled ends on top. The curly entangled mess acts like natural spatulae – when pressed against a surface, they have a large contact area and hence a strong hold.

The new material was tested for stickiness on surfaces ranging from Teflon to sandpaper. Attached to a glass surface, a single square centimetre of it can support over 1600 grams when pulled roughly parallel to the surface.

That is roughly 10 times better than some species of gecko and three times better than the best artificial competitor.

But removing a pad of the material is simple, unlike some rival materials. Pulling it perpendicular to a surface means only the tips of the nanotubes remain in contact with the surface, and the setae will easily loosen their grip. A weight of 160 grams on a square centimetre is enough to do that.