January 29, 2008

Progress to artificial gecko like wall climbing for people

Researchers at the University of California, Berkeley, have developed an adhesive that is the first to master the easy attach and easy release of the reptile's padded feet. The material could prove useful for a range of products, from climbing equipment to medical devices. One of my predictions from 2006 was that there would be artificial gecko like wall climbing. [Gecko mimicing wallcrawling suits for military and enthusiasts 2008-2012]

This collage illustrates gecko adhesion, from toes to nanostructures.
Credit: K. Autumn, Lewis and Clark College. Full resolution images are available for license, and require permission from Kellar Autumn for use (

Two centimeters on a side can support 400 grams (close to a pound). While tape sticks when it presses onto a surface, the new adhesive sticks as it slides on a surface and releases as it lifts -- this is the trick behind a gecko's speedy vertical escapes.

Therefore if this scales linearly then 300 square centimeters would support a 131 lb person. 30 cm by 10 cm would be a largish shoe. 600 square centimeters would support a 262 lb person+ gear. 200 square centimeters per foot and hand would allow one foot or hand to be moved while the other three kept contact to the wall.

The gecko-inspired adhesive can support significant weight. Increasing weight increases contact area for the adhesive (contact area is the bright area near the top of the patch). As the load increases, more fibers are recruited to make contact, increasing the strength of the adhesion parallel to the surface. When the sliding force is removed, the fibers straighten, and the patch is easily released with negligible pull-off force. The patch has demonstrated better than 1/6 of a real gecko's stress on the same glass surface.

Researchers have developed a directional adhesive, inspired by the gecko, using microfibers made from a hard polymer, polypropylene. The polymer fibers are 600 nanometers in diameter, just 1/100 the diameter of a human hair, and are formed by a casting process. Like the gecko, the synthetic microfiber array is not sticky except when fibers slide a small distance along a surface. While the present microfiber array works on smooth glass, future versions could be useful for medical equipment, sporting goods, or climbing robots where a directional and easy attach-release adhesive is needed.
Credit: J. Lee and R.S. Fearing, UC Berkeley

The current work is an improvement over the Gekkomat. It seems the current work will not need air tanks for suction and the contact pads can be smaller and less cumbersome