Many lizards such as geckos—not to mention thousands of insects—have the remarkable ability to climb up vertical surfaces with ease. The process has fascinated scientists for years, but a simple physics principle has kept bigger animals like people out of the wall-scaling game. The square cube law basically says that as objects, like animals, increase in size, their volumes grow at a much faster rate than their surface area—specifically, if you square a creature's surface area, you must cube its volume so that its body can support its own weight. This is why ants can carry more than elephants in proportion to their own weight and why small animals like geckos can more easily support themselves with small patches of adhesion.
A clearer understanding of the efficiency of a gecko's pads gave scientists hope that a more intentionally designed replica could support human weight. However, these gecko-gloves would still have to overcome the issue of evenly distributing a hanging human's weight so that no one pad was strained to the breaking point, setting off a chain reaction that could collapse the entire system.
A research team led by Stanford engineer Ethan Hawkes thinks they've solved this problem, publishing a paper on their developments last week in the Journal of the Royal Society Interface. They've developed a dry-adhesive called PDMS microwedges that utilizes gecko-inspired, hair-like nanofibers that flatten out when pulled downward against a surface and grip via electromagnetic attraction but are easily "unstuck" with a perpendicular tug.
The team attached 24 stamp-sized tiles, each of which contained hundreds of thousands of microwedges, to octagonal-shaped plates using innovative springs. These springs are the key to overcoming the gecko's limitations. Unlike traditional springs, which become tenser as you pull them like a rubber band and do not distribute weight evenly, the springs they used—made of a shape-memory alloy—exert less pressure as you pull them, like bubblegum or silly putty, and distribute weight evenly, regardless of movement. The team estimates that the plates can support up to 200 pounds. To prove their capabilities, Hawke himself climbed (rather slowly) up a glass wall.