Tiny artificial muscles flex like elephant's trunk

Posted by Kate Taylor

An international team of researchers has invented minute artificial muscles that can rotate object a thousand times their own weight.

They're strong enough to rotate objects a thousand times their own weight, but have the flexibility of an elephant’s trunk or an octopus's limbs, rotating 250 degrees per millimetre of muscle length.

The 'muscles', based on yarns made of carbon nanotubes, are more than a thousand times more flexible than currently available artificial muscles composed of shape memory alloys, conducting organic polymers or ferroelectrics.

"What’s amazing is that these barely visible yarns composed of fibres 10,000 times thinner than a human hair can move and rapidly rotate objects two thousand times their own weight," says  associate professor John Madden, of the the University of British Columbia.

WWhile not large enough to drive an arm or power a car, this new generation of artificial muscles – which are simple and inexpensive to make – could be used to make tiny valves, positioners, pumps, stirrers and flagella for use in drug discovery, precision assembly and perhaps even to propel tiny objects inside the bloodstream."
 
The nanotubes are spun into helical  yarns. This means they have left and right handed versions,  which allows the yarn to be controlled by applying an electrochemical charge, and to twist and untwist.

The nanotube yarns are activated by charging them in a salt solution, in much the same way as a battery. The helical structure of the yarns makes them unwind as they accept charge and swell, twisting back up again when discharged.