The feat that Tobey Maguire did when he played the role of Spiderman in the movies is no longer limited to works of fiction. Researchers have come up with a Gecko-inspired human climbing system that has allowed a 70-kg person to scale a glass wall using sticky pads in each hand.
Geckos are able to climb walls and move about upside down because of their incredibly sticky toes that are covered with spatula-shaped structures known as setae. These structures increase surface area and boost weak electrical attractions between the Gecko's toes and the surface.
Interestingly, while the animal's feet stick well, the Gecko has no problem releasing them, allowing it to run at a speed of 20 body-lengths per second to evade predators.
There were earlier attempts to make artificial adhesives that work the same way as the feet of this lizard, and while these have worked, they were limited for lighter weights.
Developing an adhesive that can support heavier weights, however, would have a number of potential applications and uses. No wonder that the Defense Advanced Research Projects Agency (DARPA) has worked on a project to come up with such a mechanism.
Earlier this year, DARPA announced that its Z-Man program has successfully enabled a climber weighing over 98 kg to ascend and descend a glass wall using only a pair of hand-held gecko-inspired paddles.
Although DARPA did not provide the exact details on how this was made possible, Mark Cutkosky, from the Department of Mechanical Engineering of Stanford University, and colleagues who also participated in the Z-Man work, showed a similar demonstration using the adhesive system they have developed.
For the climbing system described in their research published in the Journal of the Royal Society Interface on Nov. 19, the researchers molded polydimethylsiloxane, or PDMS, a polymer material commonly found in skin moisturizers and repellant coatings, into microwedges and then attached this into a hexagonal, hand-sized gripper with a spring intended to distribute weight across the pad and absorb some of the force exerted during climbing.
In tests, the 140-square-centimeter sticky pad has allowed a climber weighing 70 kg to scale a 3.6 meter-high vertical glass wall.
"The synthetic adhesion system creates a nearly-uniform load distribution across the whole adhesive area, improving upon the adhesive-bearing structures of a gecko's toe and enabling a human to climb vertical glass using an area of adhesive no larger than the area of a human hand," the researchers wrote. "These results show that gecko-inspired adhesives can be scaled from laboratory-scale tests to human-scale applications with little decrease in performance."