New research into how different species stick to, and then climb, walls seems to prove that no human-sized Spider-Man could ever exist. Boo.
Geckos, only a few dozen centimetres in size at the most, are the largest species to walk up walls, with it impossible for us to replicate the ability.
This, according to researchers in the UK, is because humans would need adhesive pads covering 40pc of our entire bodies just stick to the wall in the first place, let alone work out how to start moving about.
This means that, sadly, walking upright on walls perpendicular to the Earth is the stuff of fiction.
Plenty of examples
Looking at 225 different species that can climb walls, scientists from the University of Cambridge found that, in general, the heavier the animal the larger the adhesive pad (as a ratio to the species’ body) needed to be to support it on walls.
For example, tiny little mites use around 200 times less of their body surface for pads than geckos, “nature’s largest adhesion-based climbers”.
So we’d need 40pc of our entire body covered in a sticky pad, or around 40pc of our entire front.
“If a human, for example, wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet – and shoes in European size 145 or US size 114,” said Walter Federle, senior author of the study, who is based at Cambridge’s Department of Zoology.
Extra sticky feet
The only way to avoid needing a huge amount of your body surface as an adhesive pad is to have smaller areas made immensely stickier. This is incredibly rare within closely-related species, but the researchers did find some tree frogs where this was the case.
But it just isn’t sustainable for any species above the size of a gecko because, as you look up the conveyor belt of species on Earth, the larger they are the less surface area they have to the ground.
Upright walking, quite clearly, doesn’t make a Spider-Man.
Geckos at the maximum
“As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and an elephant is mostly volume with not much surface area” explained David Labonte, lead author of the study and also from Cambridge’s Department of Zoology.
“This poses a problem for larger climbing animals because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads.
“This implies that there is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko.”
The study, published in PNAS, does a couple of things. First, it disproves the potential existence of Spider-Man. Second, it proves that geckos are at the very limit of what adhesive walking can achieve in the wild. And third, it can help further research into the feasibility of large-scale, gecko-like adhesives.
“Our study emphasises the importance of scaling for animal adhesion, and scaling is also essential for improving the performance of adhesives over much larger areas,” added Labonte.
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