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Posted: April 25, 2007
Spiderman suit based on nanotechnology
(Nanowerk News) Imagine owning your own Spiderman suit, complete with gloves and boots to allow you to stick to walls, and even a sticky silk spinner to swing between buildings. That might be a step closer to reality, thanks to Nicola Pugno at the Polytechnic University of Turin in Italy, who has come up with a scheme for an adhesive material and “spider silk” based on carbon nanotubes.
Efforts to develop surface gripping materials have focused on mimicking geckos, which can hang upside down from just one toe because their feet are covered with millions of tiny elastic hairs called setae. Each seta is attracted to the wall, largely by an intermolecular force called the van der Waals force, allowing the gecko’s feet to adhere.
Researchers have previously created nanotechnology structures – carbon nanotubes – that mimic setae, but though these have around 200 times the adhesive force of gecko feet, they have yet to be scaled up to a size fit for superheroes. That’s because if you simply make the nanotubes longer, they become floppy and stick to each other rather than to the wall. On the other hand, if you make them fatter and stiffer, they become too inflexible to ensure a large enough contact area with the wall.
Now, in a paper to be published in Journal of Physics: Condensed Matter, Pugno suggests that the secret to developing an effective sticky material lies in creating a “hierarchical structure” – branching bristles of ever finer nanotubes, just as the setae of a gecko’s feet are divided at their ends into smaller branches called spatulae. Pugno calculates that this approach could result in stiff, non-tangling structures with tips still flexible enough to produce good adhesion.
Researchers at Rensselaer Polytechnic Institute in Troy, New York, have previously built similar branched nanotube structures by growing them inside aluminium oxide templates.
That just leaves the problem of swinging between buildings on Spiderman-style silk. Researchers can already spin metre-long carbon nanotube fibres (("Strong, Transparent, Multifunctional, Carbon Nanotube Sheets"), and much longer ones should be possible, so Pugno proposes making a “cable” consisting of around 4 million nanotube fibres.
Each nanotube is invisible, as they are much thinner than the wavelength of light. Pugno suggests that by anchoring the nanotubes through holes in a 1-centimetre-square spacer plate to keep the fibres 5 micrometres apart, the whole cable would remain invisible. The end of each fibre passing through the plate could be branched to create the seta structure, allowing it to stick to the target surface. Then all you would need to do is fire the cable from some kind of launcher device.
Stefano Mezzasalma at the University of Trieste in Italy says the approach could work. “The first prototype of a Spiderman suit might be ready in a decade or so.”
Source: New Scientist (D. Jason Palmer)
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