Nanotechnologist Ray Baughman from the University of Texas has been working for several years on artificial muscles made from yarn woven from nanotubes (see this post from 2007). Now, with an international team of collaborators, he has published in Science [abstract] a torsional nanotube yarn muscle and demonstrated its use as a mixer for a fluidic chip. This artificial muscle provides far more rotation than seen with previous artificial muscles, and is as flexible as an elephant’s trunk or an octopus’s arm. A video, posted by collaborators at The University of Wollongong in Australia, suggests these new “twisting artificial muscles [could] propel nano-robots one step closer to medical applications.” From the caption:

The possibility of a doctor using tiny robots in your body to diagnose and treat medical conditions is one step closer to becoming reality today, with the development of artificial muscles small and strong enough to push the tiny Nanobots along.

Although Nanorobots (Nanobots) have received much attention for the potential medical use in the body, such as cancer fighting, drug delivery and parasite removal, one major hurdle in their development has been the issue of how to propel them along in the bloodstream.

An international collaborative team led by Dr Javad Foroughi and Prof Geoff Spinks at UOW’s Intelligent Polymer Research Institute, part of the ARC Centre of Excellence for Electromaterials Science (ACES), have developed a new twisting artificial muscle that could be used for propelling nanobots. The muscles use very tough and highly flexible yarns of carbon nanotubes (nanoscale cylinders of carbon), which are twist-spun into the required form. When voltage is applied, the yarns rotate up to 600 revolutions per minute, then rotate in reverse when the voltage is changed.

Due to their complexity, conventional motors are very difficult to miniaturise, making them unsuitable for use in nanorobotics. The twisting artificial muscles, on the other hand, are simple and inexpensive to construct either in very long, or in millimetre lengths. …

Further details are available on EurekAlert from the University of Texas at Dallas “Carbon nanotube muscles generate giant twist for novel motors“:

Twist per muscle length is over a thousand times higher than for previous artificial muscles and the muscle diameter is ten times smaller than a human hair

New artificial muscles that twist like the trunk of an elephant, but provide a thousand times higher rotation per length, were announced on Oct. 13 for a publication in Science magazine by a team of researchers from The University of Texas at Dallas, The University of Wollongong in Australia, The University of British Columbia in Canada, and Hanyang University in Korea.

These muscles, based on carbon nanotubes yarns, accelerate a 2000 times heavier paddle up to 590 revolutions per minute in 1.2 seconds, and then reverse this rotation when the applied voltage is changed. The demonstrated rotation of 250 per millimeter of muscle length is over a thousand times that of previous artificial muscles, which are based on ferroelectrics, shape memory alloys, or conducting organic polymers. The output power per yarn weight is comparable to that for large electric motors, and the weight-normalized performance of these conventional electric motors severely degrades when they are downsized to millimeter scale. …

The combination of mechanical simplicity, giant torsional rotations, high rotation rates, and micron-size yarn diameters are attractive for applications, such as microfluidic pumps, valve drives, and mixers. In a fluidic mixer demonstrated by the researchers, a 15 micron diameter yarn rotated a 200 times larger radius and 80 times heavier paddle in flowing liquids at up to one rotation per second. …

A EurekAlert release from the University of British Columbia adds:

… Using yarns of carbon nanotubes that are enormously strong, tough and highly flexible, the researchers developed artificial muscles that can rotate 250 degrees per millimetre of muscle length. This is more than a thousand times that of available artificial muscles composed of shape memory alloys, conducting organic polymers or ferroelectrics, a class of materials that can hold both positive and negative electric charges, even in the absence of voltage.

“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 UBC Assoc. Prof. John Madden, Dept. of Electrical and Computer Engineering.

Madden says, “While 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.”

Central to the team’s success are nanotubes that are spun into helical yarns, which means that they have left and right handed versions, which allows the yearn to be controlled by applying an electrochemical charge, and to twist and untwist.…