Carbon nanotube ‘muscles’ could aid drug delivery

Artificial muscles strong enough to rotate objects 1,000 times their own weight have been invented by an international team of researchers.

The development could lead to the realisation of a propulsion system for nanorobots that can deliver drugs or remove parasites.

Using yarns of carbon nanotubes, the researchers developed artificial muscles that can rotate 250° per millimetre of muscle length.

This is claimed to be more than 1,000 times that of available artificial muscles, composed of either shape-memory alloys, conducting organic polymers; or ferroelectrics, a class of materials that can hold positive and negative electric charges even in the absence of voltage.

In a statement, associate Prof John Madden, of the UBC Department of Electrical and Computer Engineering, said: ‘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 2,000 times their own weight.

‘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 team claims that nanotubes spun into helical yarns are central to the team’s success as they allow the yarn to be controlled by applying an electrochemical charge, and to twist and untwist.

The material was devised at the University of Texas at Dallas and then tested as an artificial muscle in Madden’s lab at UBC. A chance discovery by collaborators from Wollongong showed the enormous twist delivered by the device. Guided by theory at UBC and further experiments in Wollongong and Texas, the team was able to extract torsion and power from the yarns.

The nanotube yarns are activated by charging them in a salt solution and deformation of the yarns is reportedly proportional to the size and number of ions inserted.

Details of the work, which included input from researchers at Hanyang University in Korea, can be found on Science Express.