Scientists have created a new material that is stronger than steel and stiffer than diamond, weighs little more than its volume in air, and could be the perfect artificial muscle for robots.
According to a report in New Scientist, scientists at the University of Texas, Dallas, US, developed the material.
“We’ve made a totally new type of artificial muscle that is able to provide performance characteristics that have not previously been obtained,” said Ray Baughman, a materials scientist at the University of Texas, and co-developer of the new muscle.
Baughman and colleagues have developed a technique to make ribbons of tangled nanotubes that expand in width by 220 percent when a voltage is applied and then return to their normal size once it is removed.
The process takes only milliseconds.
“Collections of those ribbons could act as artificial muscle fibres – for example, to move the limbs of a walking robot,” said Baughman.
The material has other impressive properties.
It is extremely stiff and strong in the “long” direction – that in which the nanotubes are aligned – but is as stretchy as rubber across its width.
It also maintains its properties over an extreme range of temperatures: from -196 degrees Celsius, at which temperature nitrogen is liquid, to 1538 degrees C, above the melting point of iron.
This means any robot equipped with the nanotube muscles could potentially keep working in some very extreme environments.
The new material has some advantages over previous artificial muscles.
Some of those work only when bathed in methanol fuel, others are capable of only very small changes in size and none of them work well at extreme temperatures.
The tangled nanotubes are constructed into a film that can be described as an aerogel, meaning it contains more air than anything else.
Ribbons of the aerogel are made by first growing “forests” of carbon nanotubes that resemble a dense thicket of bamboo stalks.
The researchers then stick a length of adhesive to the sides of those stalks and pull gently to draw out a long, thin film of the tubes, which tangle during the process.
So far, ribbons a 50th of a millimeter thick by 16 centimeters wide and several meters long have been made, but it should be possible to form larger sheets by starting with more nanotubes.
According to Electrical engineer John Madden at the University of British Columbia, resilience and low density could make it a good material for building structures in space, with its lightness keeping down the cost of sending a payload into orbit.
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