Ultra-Strong, Flexible Carbon Nanotube Artificial Muscle Invented

in technology, medicine

A team of scientists have invented new artificial muscles strong enough to rotate objects a thousand times their own weight, but with the same flexibility of an elephant’s trunk or octopus limbs.  The new twisting artificial muscle could be used for propelling nano robots.

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

ultra strong and flexible carbon nanotube muscle fiber
Image credit:ARC Centre of Excellence for Electromaterials Science.

“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 Prof. John Madden, University of British Columbia Dept. of Electrical and Computer Engineering.

The paper appeared today in the journal Science.

In the animated video above, first see a few bacteria like creatures swimming about. Their rotating flagella are highlighted with some detail of the flagella motor turning the “hook” and “filament” parts of the tail. Next see a similar type of rotating tail produced by a length of carbon nanotube thread that is inside a futuristic microbot. The yarn is immersed in a liquid electrolyte along with another electrode wire. Batteries and an electrical circuit are also inside the bot. When a voltage is applied the yarn partially untwists and turns the filament. Slow discharging of the yarn causes it to re-twist. In this way, one can imagine the micro-bot is propelled along in a series of short spurts (credit:ARC Centre of Excellence for Electromaterials Science).

Although Nanorobots 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.

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.

“This new, giant, rotating type of actuation will open up lots of new opportunities for micro-machines,” said Prof Geoff Spinks, Chief Investigator at ARC Centre of Excellence for Electromaterials Science, Australia.

Similar twisting muscles are found in nature, such as octopus limbs and elephant trunks.   In these appendages, helically wound muscle fibres rotate by contracting against an incompressible, bone-less core.  The rotation in the helically wound carbon nanotubes used for the twisting artificial muscles is caused by an increase of liquid electrolyte volume within the yarn.

Source Article: Torsional Carbon Nanotube Artificial Muscles. Javad Foroughi, Geoffrey M. Spinks, Gordon G. Wallace, Jiyoung Oh, Mikhail E. Kozlov, Shaoli Fang, Tissaphern Mirfakhrai, John D. W. Madden, Min Kyoon Shin, Seon Jeong Kim, and Ray H. Baughman. Science 13 October 2011: 1211220. Published online 13 October 2011. DOI:10.1126/science.1211220.

Additional Sources: University of British Columbia and  ARC Centre of Excellence for Electromaterials Science.

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