A professor from the
Polytechnic
of Turin has developed a method for building a suit that could allow humans
to cling to vertical surfaces like the comic book hero
Spiderman.
The suit would use a similar principle used by geckos and spiders, which
possess millions of tiny hairs on their limbs allowing them to stick to
surfaces.
It is generally accepted that the microscopic hairs adhere to the surfaces,
not by gripping in the traditional sense, but by using intermolecular phenomena
called van der Waal forces, which are the same that allow an atom's protons not
to burst apart.
Adhesion strength drops exponentially as the surface area and weight
increases, so creating the same effect in a human-sized subject has been
considered impossible.
However, Professor Nicola Pugno has calculated how sufficient stickiness
could be generated in the same way to support an adult human's bodyweight.
This would be achieved by creating gloves and shoes coated in an hierarchical
structure of carbon nanotubes to provide the same effect.
The grip of the gloves could be released with little effort by a peeling
motion, which would break the adhesion little by little.
"Some researchers were able to measure an adhesion strength 200 times higher
than that of a gecko. But there is a large gap between theory and practical
applications," said Professor Pugno.
"If we are able to make a surface a little bit stronger, so that the size
effect vanishes, we might be able to make a suit with the same adhesion as a
gecko."
Professor Pugno predicted that we could see such suits by 2017, but added
that they will need to be adhesive enough, easily detachable and self-cleaning
if they are to be feasible.
"By using something like nanotubes we should be able to create sufficient
attractive force to easily support a human, and by laying them out a
hierarchical structure, the user should be able easily detach each limb in a
simple peeling motion," he said.
The last requirement is slightly less obvious. The nature of the design means
that tiny dirt particles could begin to clog up the nanotube fibres, gradually
reducing the stickiness of the suit.
One method of counteracting this would be to make the suit hydrophobic, so
that it strongly repels water. As water droplets are forced away from the
contact areas of the outfit, they should wash away particles of dirt.
"To have all these mechanisms working together is difficult, because they are
in competition with one another," Professor Pugno told the
BBC News
website. "But geckos and spiders provide a natural demonstration that this can
be done."
Professor Pugno sees many useful applications for such a suit, ranging from
window cleaning to space exploration.
The findings have been published in the
Journal
of Physics: Condensed Matter.
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