Liming Dai of the University of Dayton, Ohio and Zhong Lin Wang of Georgia Institute of Technology have revealed that they’ve constructed a material made up of nanotubes that uses the same principle as a gecko’s feet to stick to surfaces, and although it does it ten times more powerfully, the dry glue is still easily unstuck with a pull in the right direction.

The feet of a gecko are covered in small hair strands called setae, which are branched at the end, the branches being called spatulae. When the gecko touches a surface, the setae spread and increase the surface area that’s in contact with whatever the lizard is walking on. Thanks to Van der Waal molecular forces at work, the gecko’s small foot can sustain its entire body stuck fast to the surface.

The two researchers were able, using carbon nanotubes, which were grown in a silicon wafer, to replicate the gecko’s setae. Their synthetic material however, is ten times more adherent than the gecko’s natural setae. The adhesive force of the material is about 100 newtons per square centimeter. One square inch (2.5cm²) is able to hold the weight of a 220 pound (100) kg man climbing up a vertical surface.

The catch here, and also the most interesting thing about the material, is that while the nanotubes are parallel to the contact surface, the bond is very strong.  However when the tubes are pulled perpendicularly to the surface, say if the same man tried to stick to the ceiling, then the bonds are loosed and the nanotubes pull free with little effort. This could have very interesting applications in climbing/maintenance robots.

A problem that will have to be overcome is that of dirt, but thanks to the versatility of the nanotubes, Professor Dai says he could coat the material with proteins that change their shape with changes in temperature. Thus, they could heat said robot’s feet when they got clogged with dirt, and it would shake the dirt off. If it works, it will be the first adhesive inspired by the gecko’s feet that can address the dirt problem (there have been attempts based on the same principle before, but they’ve failed because of just this reason).

Carbon nanotubes are also very conducive to electricity and have very interesting thermal properties. Professor Dai sees such applications for his technology as in electronics, to replace soldering and act as heat sinks, or in the aerospace industry, where adhesives are a problem due to the fact that the extreme temperature shifts of space make polymer-based adhesives fail.

As for using nanotubes for creating the spider-man suit, Professor Liming Day commented that “We will exploit this possibility, if there is a serious need.”