Wax-infused "nanoyarn" used to create artificial muscles


November 19, 2012

Individual nanotubes can be 10,000 times smaller than the diameter of a human hair, yet 100 times stronger than steel, pound-for-pound

Individual nanotubes can be 10,000 times smaller than the diameter of a human hair, yet 100 times stronger than steel, pound-for-pound

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An international team of scientists based at the University of Texas, Dallas (UTD), has developed a new type of artificial muscle created from carbon “nanotubes” – tiny hollow cylinders constructed from the same graphite layers found in the core of a standard pencil. Despite measuring 10,000 times less than the diameter of a human hair, the new muscles can lift more than 100,000 times their own weight, which amounts to approximately 85 times the power of a natural muscle of equivalent size.

The new muscles are manufactured by taking a twisted yarn of the miniscule carbon cylinders, then introducing a volume-changing “guest,” in this case the paraffin wax used in candles.

The wax-coated yarn is then heated either electrically, or with a flash of light, and this causes the wax to expand, with the yarn volume increasing, and the length of the material contracting as a result. This muscle contraction, or actuation, can occur in just 25 thousandths of a second. Taking into account times for both actuation and reversal of the actuation, the UTD researchers demonstrated a contractile power density of 4.2 kW/kg, four times the power-to-weight ratio of a typical internal combustion engine.

However, while the new technology has many applications, it is not expected to be used in the human body, for now at least. This contrasts with the somewhat similar research into artificial muscles for nanobots we reported on last year.

“The artificial muscles that we’ve developed can provide large, ultrafast contractions to lift weights that are 200 times heavier than possible for a natural muscle of the same size,” explained Dr. Ray Baughman, team leader, Robert A. Welch Professor of Chemistry and director of the Alan G. MacDiarmid NanoTech Institute at UT Dallas. “While we are excited about near-term applications possibilities, these artificial muscles are presently unsuitable for directly replacing muscles in the human body.”

Dr. Baughman further explains that because of the simplicity of their construction and high-performance, the new artificial yarn muscles may be implemented in a variety of areas, such as catheters for minimally invasive surgery, microvalves, toys, and robots. The muscles could also be employed in self-powered intelligent materials, such as a protective suit which reacts to changes in environmental temperature in order to offer the wearer appropriate levels of protection, for example.

In addition, testing shows that the wax-infused carbon tubes are able to withstand temperatures 1,000 C (1,832 Fahrenheit) above the melting point of steel, where no other current actuator can operate.

The next challenge for the UTD researchers is to upscale the single-yarn muscles, to larger and more complex systems which implement thousands of yarn muscles in parallel.

The research was detailed in a study published in the November 16 issue of the journal Science. In the video below, Dr. Baughman explains the research further.

Source: UTD

About the Author
Adam Williams Adam scours the globe from his home in North Wales in order to bring the best of innovative architecture and sustainable design to the pages of Gizmag. Most of his spare time is spent dabbling in music, tinkering with old Macintosh computers and trying to keep his even older VW bus on the road. All articles by Adam Williams

If they could run an electrical current through the nanotubes to heat them then this might be a good power source for small ornithopter type flying machines.

Michael Crumpton

The high heat capabilities are very interesting to me

Racqia Dvorak

Unlikely, Michaelc - remember that carbon nanotubes have practically zero electrical resistance and would not heat up very much from small amounts of current. A more likely solution is to surround or infuse each "muscle fiber" with an electric heating element.

This is crazy stuff, though. My mind is completely blown. Were a human to have their muscles replaced with this stuff (and their bones with something stronger, since that amount of strength would otherwise tear them apart), knocking down the Empire State Building would be child's play for them.

Joel Detrow

Was anyone else thinking of Crysis while reading this?


They would receive Nobel prize, I guess.

Keun-Ho Rew

All you have to is figure out a micro heating system then just mimic the muscle structures of living things Instant robots of all shapes and sizes with low power requirements add in IBM's neural computing technology and we can be in for good times or huge trouble.

Joseph Mertens

It does have obvious excellent implications for possibillities in the realm of prosthetics but I wonder about whether or not a heat disipation obsticle might present when the tech' is scaled up. As I understand it rapid cooling is a neccesity for for muscular relaxation, (hence tension let up), in thos model to occur. For that matter, what affect might simple ambient atmospheric temperature variations cause? Varients in "muscle tone"? I suppose some sort of simulated vascular coolant system could be the answere to maintaining proper operating temp & means of hastend heat disapation.

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