Wax-filled nanotech yarn behaves like powerful, super-strong muscle (w/ video)

New artificial muscles made from nanotech yarns and infused with paraffin wax can lift more than 100,000 times their own weight and generate 85 times more mechanical power during contraction than the same size natural muscle, according to scientists at The University of Texas at Dallas and their international team from Australia, China, South Korea, Canada and Brazil.

The are yarns constructed from carbon nanotubes, which are seamless, hollow cylinders made from the same type of graphite layers found in the core of ordinary pencils. Individual nanotubes can be 10,000 times smaller than the diameter of a human hair, yet, pound-for-pound, can be 100 times stronger than steel.

"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," said Dr. Ray Baughman [pronounced BAK-man], 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. Ray Baughman, University of Texas at Dallas, describes carbon nanotube yarns. Credit: University of Texas at Dallas

Described in a study published online today in the journal Science, the new artificial muscles are made by infiltrating a volume-changing "guest," such as the paraffin wax used for candles, into twisted yarn made of carbon nanotubes. Heating the wax-filled yarn, either electrically or using a flash of light, causes the wax to expand, the yarn volume to increase, and the yarn length to contract.

The combination of yarn volume increase with yarn length decrease results from the produced by twisting the yarn. A child's finger cuff toy, which is designed to trap a person's fingers in both ends of a helically woven cylinder, has an analogous action. To escape, one must push the fingers together, which contracts the tube's length and expands its volume and diameter.

"Because of their simplicity and high performance, these yarn muscles could be used for such diverse applications as robots, catheters for minimally invasive surgery, micromotors, mixers for microfluidic circuits, tunable optical systems, microvalves, positioners and even toys," Baughman said.

Muscle contraction – also called actuation – can be ultrafast, occurring in 25-thousandths of a second. Including times for both actuation and reversal of actuation, the researchers demonstrated a contractile power density of 4.2 kW/kg, which is four times the power-to-weight ratio of common internal combustion engines.

To achieve these results, the guest-filled muscles were highly twisted to produce coiling, as with the coiling seen of a rubber band of a rubber-band-powered model airplane.

When free to rotate, a wax-filled yarn untwists as it is heated electrically or by a pulse of light. This rotation reverses when heating is stopped and the yarn cools. Such torsional action of the yarn can rotate an attached paddle to an average speed of 11,500 revolutions per minute for more than 2 million reversible cycles. Pound-per-pound, the generated torque is slightly higher than obtained for large electric motors, Baughman said.

Because the yarn muscles can be twisted together and are able to be woven, sewn, braided and knotted, they might eventually be deployed in a variety of self-powered intelligent materials and textiles. For example, changes in environmental temperature or the presence of chemical agents can change guest volume; such actuation could change textile porosity to provide thermal comfort or chemical protection. Such yarn muscles also might be used to regulate a flow valve in response to detected chemicals, or adjust window blind opening in response to ambient temperature.

Even without the addition of a guest material, the co-authors found that introducing coiling to the nanotube yarn increases tenfold the yarn's thermal expansion coefficient. This thermal expansion coefficient is negative, meaning that the unfilled yarn contracts as it is heated. Heating the yarn in inert atmosphere from room temperature to about 2,500 degrees Celsius provided more than 7 percent contraction when lifting heavy loads, indicating that these muscles can be deployed to temperatures 1000 C above the melting point of steel, where no other high-work-capacity actuator can survive.

"This greatly amplified thermal expansion for the coiled yarns indicates that they can be used as intelligent materials for temperature regulation between 50 C below zero and 2,500 C," said Dr. Márcio Lima, a research associate in the NanoTech Institute at UT Dallas who was co-lead author of the Science paper with graduate student Na Li of Nankai University and the NanoTech Institute.

"The remarkable performance of our yarn muscle and our present ability to fabricate kilometer-length yarns suggest the feasibility of early commercialization as small actuators comprising centimeter-scale yarn length," Baughman said. "The more difficult challenge is in upscaling our single-yarn actuators to large actuators in which hundreds or thousands of individual yarn muscles operate in parallel."

Explore further

Carbon nanotube muscles generate giant twist for novel motors

More information: "Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles," by M.D. Lima, et al. Science, 2012.
Journal information: Science

Citation: Wax-filled nanotech yarn behaves like powerful, super-strong muscle (w/ video) (2012, November 15) retrieved 23 July 2019 from https://phys.org/news/2012-11-wax-filled-nanotech-yarn-powerful-super-strong.html
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User comments

Nov 15, 2012
"While we are excited about near-term applications possibilities, these artificial muscles are presently unsuitable for directly replacing muscles in the human body."

Well, yeah, they'd snap human bones like dry sticks.

That was meant as a joke, BTW.

Nov 15, 2012
Even though "these artificial muscles are presently unsuitable for directly replacing muscles in the human body" I suspect at some time they might be.

There goes sports.

Nov 15, 2012
Latest new show... the 6 trillion dollar man!

Nov 15, 2012
It's actually rather incremental progress, because we have number of powerful nanotube muscles already and the heating is not the most effective way, how to power them - but it's still a progress. You may want to check additional videos here

Nov 15, 2012
Whats interesting in terms of reversibility, is the suggestion the wax doesnt deform through or around the tubes/yarns, probably due to relative sizes of the molecules. This implies a material with a larger structure and with repository for sensory materials could perform with even larger range of motion yet remain trapped in the coiled nanotube and provide a wide range of tightly integrated functions in a very small space. Well, for the time being at least.

The potential for artificial insects and the like building programmed structures seems a rather more present and accessible practical potential than molecular manufacturing devices.

The economics of making carbon nanotubes in a variety of types would therefore be of considerable interest :-)

Nov 15, 2012
I wonder what the energy consumption of the 'muscle' is? This material could perhaps be used as an interesting technology addition to a Serling engine..

Nov 15, 2012
RobL gave me the heebie jeebies
I wonder what the energy consumption of the 'muscle' is? This material could perhaps be used as an interesting technology addition to a Serling engine..
Yikes you mean Rod Serling as in "The Twilight Zone", de do de do, de do de do de !

I think you meant this:- http://en.wikiped...g_engine

And sure, if the working fluid isnt too hot and doesnt dissolve the wax eg water then it can contact the material directly for best heat transfer so the efficieny is just related to the energy of latent heat of fusion, make for some interesting maths :-)

With the right scaling it could make for some very very small 'hands' and if the control is precise with telepresence as well could offer some very good fast feedback to force actuators one can then *cough* get a grip on !

I'd love to make my own nanotubes, but maybe we wouldnt need to, just get some fine linen yarns and cook them in absence of oxygen might be an interesting experiment :-)

Nov 16, 2012
MULHALL: Thank you. Have you prepared the negaton hydracoils for the drawing Sargon supplied?

SCOTT: For all the good it'll do you. It's a fancy name, but how will something that looks like a drop of jelly make this thing work? You'll need microgears and a pulley that does what a muscle does.

MULHALL: That would be highly inefficient.

SCOTT: I tell you, lady, this thing won't work.

SPOCK: It will have twice the strength and agility of your body, engineer, and will last a thousand years. That is, assuming you'll stop wasting your time and allow us to complete it.

Return to Tomorrow

Nov 16, 2012
is there a market for this in the sex toys business?

Nov 16, 2012
This would be extremely useful for micro-manipulators such as tele-surgery.

Nov 19, 2012
One could put it on a crank, to produce
rotating mechanical energy. When you heat
it with concentrated solar power and alternatedly
putting it in shadow and cooling, you have a solar

Nov 19, 2012
When you heat it with concentrated solar power and alternatedly putting it in shadow and cooling, you have a solar engine.

Since the light/dark cycle happens only once a day you'd not have much of an engine.

However these fibers could be used to replace the passive liquid or gas driven trackers for solar panels. It would eliminate any maintenance needed due to losses of the driving fluid/gas.

Nov 19, 2012
How about putting these fibers into disk, like spokes in a bicycle wheel and expose only part of that wheel to sunlight. With suitable ratcheting system the disk should rotate, allowing cooling of the fibers that are not illuminated. One should then be able to extract energy from the rotation of the disk.

Nov 20, 2012
Most plastics will expand with heat so a simple piston/cylinder device could be used in fact the thermostat in your car engine uses a device like this to control the flow of coolant.

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