[Image Source: The Royal Society]
Check out the video below that shows Elliot Hawkes, a mechanical engineer at Stanford, climb the wall like Spider-man using a pair of gecko inspired adhesive gloves.
“To work, the surface you’re climbing needs to be relatively smooth; like glass, varnished wood, polished stone, or metal,” Hawkes says, “but you can attach and detach with very little effort, and to make [the gloves] stick all you have to do is hang your weight.”
Scientists are constantly taking a page out of nature’s book, however, scaling up the feet of a gecko wasn’t all that simple. The challenge was to figure out how to delicately balance the strain of a climbing human hand across a big patch of adhesive. And there’s a reason that you never see large creatures with this ability, the cube law.
The cube law is a law in physics that says the bigger you get, the more volume you must have in relation to your surface area (if you square a creature’s surface area, you must cube its volume so that its body can support its own weight). However, Eric Eason, a physicist at Stanford who helped develop the gloves, points out that gecko feet are actually inefficient—only a small fraction of the pad ever touches a flat surface and the weight is unevenly distributed.
The gloves work thanks to a dry-adhesive created by the team called PDMS microwedges. The adhesive works via clingy hair-like nanofibers that flatten out when pulled downward against a surface. They grip using electromagnetic attraction (called the van der Waals force) but can be easily removed when pulled off perpendicularly.
In tests, the 70 kg climber successfully scaled a 3.6m-high vertical glass wall using 140 sq cm silicone pads in each hand. The climber tested the adhesive hundreds of times on the wall without failure.
“This is a really big deal. I’ve been dreaming about this for about 15 years, since we first discovered the mechanism that makes geckos stick to walls. And this is proof that we finally understood it well enough to make a person climb a building,” says Kellar Autumn, a biomechanical engineer at Lewis & Clark College who studies gecko adhesion.
They’re not perfect of course. The gloves won’t work in the rain and they require a pretty flat surface to work. They also collect dirt and dust the more they are used meaning they become less effective over time, however, cleaning them is as easy as pressing them against sticky tape.
Check out the full research publication here.