Gecko-Gloves for Climbing Like Spiderman
Most of us would have watched Spiderman scaling the side of a building using just his hands and wondered what it would be like if it were really possible to be able to do such a thing. Well, now it is possible, thanks to scientists from Stanford University in the US.
The team, led by mechanical engineer Professor Mark Cutkosky, have developed hand pads that have been inspired by geckos. The pads were so successful that they enabled one of the team to climb and down a vertical glass wall multiple times without failing even once. Their findings have been published in the Journal of the Royal Society Interface.
Geckos use something called van der Waals forces to stick to what they are climbing. The force is actually relatively weak but is multiplied by lots of tiny frills that cover the underside of a gecko’s foot. These frills, called setae, effectively increase the surface area of the toes, thus boosting the electrical attraction between the gecko and the surface it clings to and producing a dry adhesive.
The hand pads, made of silicone, use the same forces to stick to the wall, but on a larger scale. Along the same lines as a gecko’s tiny toe-hairs, the team created micro-wedges, which are small tiles that are able to harness the adhesive power.
Using this method, researchers were able to create a dry adhesive, like that from the gecko but even more efficient – which they found out during testing.
PhD candidate Elliot Hawkes was the volunteer climber to climb a 3.6m/12ft tall vertical glass wall using only a 140cm² pad on each hand. Hawkes, who weighs around 11 stone (70kg/154lb), found that the pads easily peeled on and off of the glass surface. Despite this, he was still able to test the pads hundreds of times without them losing any of their stickiness.
“As the load [on the micro-wedges] increase, the tendons and springs ensure that all tiles converge to the same maximum load,” said Professor Cutkosky. He explained that if this didn’t happen, then one of the tiles would fail. And if one tile fails, they all fail. “The failure proceeds like an avalanche across the entire array.”
One problem the team did come across, however, was that the pads didn’t perform as well on rough surfaces as on smooth, clean glass. That is the one area that a gecko is able to outperform the pads. Hawkes suggested that to overcome this, the tiles on the pads could be made smaller.
“On contaminated surfaces, even geckos have trouble producing adhesions,” Hawkes pointed out. He added that the micro-wedges on the silicone pads could be cleaned after each step using materials like sticky tape, which have a higher surface energy. This could ultimately lead to the pads becoming self-cleaning.
Professor Cutkosky explained that past efforts involving some kinds of “spider-suit” don’t work because they don’t take into account that humans tend to have more strength in their legs than in their arms. But the professor now thinks that a system could be created whereby the silicone pads on the hands were connected to the feet with cables and links to transfer the load.