Your childhood dreams of becoming Spider-man are one step closer to reality thanks to scientists at Stanford University. No, unfortunately they can’t make you shoot webs out of your wrists, but their new invention does allow humans to scale vertical glass walls. This impressive feat was achieved using Stanford’s new hand-sized, gecko-inspired sticky pads. They might not look quite as swanky as Tom Cruise’s gloves in Mission: Impossible-Ghost Protocol, but they’re awesome nonetheless.
Geckos are able to effortlessly scurry up walls and along ceilings thanks to millions of microscopic hairs on the bottom of their feet called setae. These setae, which like our own hair are made of keratin, are covered in hundreds of even smaller projections called spatulae. These bristles increase the surface area of the foot and also amplify weak attractions, called van der Waals interactions, between molecules on the toes and the surface. Importantly, the bonds between the two surfaces are easily broken when the gecko shifts its weight, allowing the animal to quickly detach and re-attach again and again, a characteristic that most man-made adhesives do not possess.
Researchers have attempted to make gecko-style adhesives before, for example by using microscopic wedges or carbon nanotubes to mimic the setae, but they’ve failed to overcome issues with scaling. Supporting large weights requires large surface areas, but stickiness starts to diminish as size increases. Even the mighty gecko has this problem; if it used all of its setae at the same time, it could support 130 kilograms (280 pounds). But because only a small percentage of the setae are in contact with the surface at any one time, the gecko can only lift around two kilograms (4.4 pounds). Furthermore, the setae don’t share the load equally, which is a problem that adhesives with large surface areas also struggle with.
But Stanford scientists found a way to overcome this, which is why their new adhesive outperforms earlier attempts. First, they created thousands of microscopic wedges using silicone, and assembled them onto postage stamp-sized tiles. These tiles, which were arranged on a hand-sized plate, were connected to springs that distributed the weight evenly across the pad. The grippers were also connected to a platform for the climber’s feet, transferring most of the effort to the legs.
During a demonstration, a 70 kilogram (154 pound) man was able to ascend a 3.6 meter vertical glass wall using the new climbing pads. To achieve this using previously designed materials, the pads would have had to be around 10 times the size of a normal human hand.
This isn’t the first time that gecko-inspired climbing pads have been made; the U.S. Defense Advanced Research Projects Agency (DARPA) recently showcased their device, although they didn’t give out details of how they created theirs, and they were significantly larger than the Stanford team’s pads.
DARPA hopes that their climbing pads could help soldiers scale buildings and obstacles more easily, but the Stanford team envision their material could have a place in space, helping astronauts or robots maneuver themselves. The scientists are now working with NASA and testing out their material in extreme conditions, such as zero-gravity.
[Via Science, MIT, the Guardian and the Journal of the Royal Society Interface]
