A new material that is weight for weight stronger than steel and stiffer than diamond, and weighs little more than its volume in air, could be the perfect artificial muscle for robots.
“We’ve made a totally new type of artificial muscle that is able to provide performance characteristics that have not previously been obtained,” says Ray Baughman, a materials scientist at the University of Texas, Dallas, 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% 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, says Baughman. And 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 °C, at which temperature nitrogen is liquid, to 1538 °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.