Spiderman can't exist in real world: study

Spiderman, a fictional superhero appearing in American comic books and Hollywood movies, can't exist in our real world, said a new research released Monday by a team of British scientists.

The study, published in the U.S. journal Proceedings of the National Academy of Sciences, revealed that geckos are the largest animals able to scale smooth vertical walls using sticky footpads.

To come to this conclusion, David Labonte and his colleagues in the University of Cambridge's Department of Zoology compared the weight and footpad size of 225 climbing animal species including insects, frogs, spiders, lizards and even a mammal.

They found that the adhesive area of the animals' footpads increased in proportion to weight. For example, geckos, nature's largest adhesion-based climbers, use about 200 times more of their total body area for adhesive pads than tiny mites.

Such scaling sets a limit to the size of animal that can use this strategy because larger animals would require impossibly big feet, they said.

"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 a blue whale is mostly volume with not much surface area," Labonte said.

"This poses a problem for larger climbing species because, when they are bigger and heavier, they need more sticking power to be able to adhere to vertical or inverted surfaces, but they have comparatively less body surface available to cover with sticky footpads," said Labonte.

"This implies that there is a size limit to sticky footpads as an evolutionary solution to climbing -- and that turns out to be about the size of a gecko."

Following that scaling law, a human would need adhesive pads covering 40 percent of their body, surface, or roughly 80 percent of their front, in order to walk up a wall like Spiderman.

"If a human wanted to walk up a wall the way a gecko does, we'd need impractically large sticky feet -- our shoes would need to be a European size 145 or a US size 114," added Walter Federle, senior author also from Cambridge's Department of Zoology.

Actually, larger animals in nature have evolved practical strategies to help them climb, such as claws and toes to grip with.

The researchers hoped that these insights into the size limits of sticky footpads could have profound implications for developing large-scale bio-inspired adhesives, which are currently only effective on very small areas. Endit