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Spiderman suit should have been hairy


Spiderman's suit could have had thousands of tiny hairs on the outside to act like molecular velcro (Image: Reuters/Sukree Sukplang)

Scaling tall buildings may have been easier if Spiderman's suit was covered in thousands of tiny hairs, new research suggests.

A team from Germany and Switzerland found that a type of jumping spider can climb smooth surfaces because thousands of tiny hairs act like molecular velcro.

Knowing how these tiny hairs work could help scientists design better spacesuits or robots, one researcher says.

Professor Antonia Kesel from the University of Applied Sciences in Bremen and team published their work in the current issue of the journal Smart Materials and Structures.

Scientists knew that spiders used claws to cling to rough surfaces. But until now no-one knew exactly how well spiders stuck to smooth surfaces, even when upside down.

The researchers looked at the claw tufts or scopulae on the feet of a jumping spider Evarcha arcuata.

The claw tufts are made up of fine hairs, called setae, and these are made up of about 624,000 even finer hairs or setules.

The setules are so small, they can get very close to a surface and interact with it at the molecular level, using weak electromagnetic or van der Waals' forces.

As these forces operate independently of material properties and the surrounding environment, adhesion should be stable under wet or greasy conditions or even in outer space, the researchers said.

Using atomic force microscopy the team determined the average adhesive force of an individual setule. The researchers then calculated the adhesive force for all the setules.

They calculated that the jumping spider could carry more than 170 times its own body weight before coming unstuck.

"That's like Spiderman clinging to the flat surface of a window on a building with his fingertips and toes only, while rescuing 170 adults who are hanging onto his back," said Kesel's colleague and co-author Andrew Martin.

Many insects and spiders can stick to surfaces and do this using claw or clamp-like structures.

Some insects produce liquids that add surface tension forces, improving adhesion. But insects don't adhere to surfaces as well as spiders, and spiders don't produce these liquids.

It is likely that the spider moves its feet by gradually attaching setules to and detaching them from a surface, in a peeling motion, the researchers said.

The mechanism and motion in the spider mirrors what scientists had previously seen with geckoes.

This form of molecular velcro may have applications in industry.

Australian researcher Associate Professor Lachlan Thompson from Melbourne's RMIT University was impressed with the research.

"It opens up a whole new avenue for design of devices that pick up and carry things, called end-effectors, used in robotics," he said.

"There are [also] major problems in composites manufacturing where they make aircraft [and] spacecraft components, using carbon fibre-based material. There's a lot of interest in using techniques, perhaps using van der Waals' forces. To date that's been quite ineffective."

Thompson also thought the hairs' sticking power would be useful in space.

"It could open the way for better spacesuits for astronauts. At the moment an astronaut goes out into space and has great trouble manoeuvring. But if you could use this technique you could walk along the outer surface of the spacecraft quite safely," he said.

"You could pick things up literally with the palm of your hand, depending on the sophistication of the control that was developed. You could be able to get the dexterity that you'd like to have in a spacesuit, which at the moment is like trying to pick something up with boxing gloves."

Tags: environment, engineering, entomology