The development of artificial muscles, made from twisted strands of carbon yarn, could power the limbs of super-strong robots in the future.
The twisted strands of carbon yarn can pull more than 100,000 times their own weight as tests demonstrate over 200 times the lifting-load capacities of natural muscles.
Scientists state the material, which can be woven into fabric, has multiple potential applications.
Alongside giving robots strength, these carbon-muscles could be used to operate valves and other engineering systems, or be incorporated into "smart" clothing that reacts to its environment as acting motors.
For technical reasons, they are unsuitable for replacing lost or damaged muscle in the human body.
The muscles are made from carbon nanotubes, hollow strands of carbon 10,000 times thinner than human hair yet 100 times stronger than steel.
The yarn is soaked in wax then shaped into a coiled structure. When heated by electricity or light the wax will expand to cause the yarn to contract and twist. This process is reversed when the heated ceases and the yarn cools. Like a rubber band in toy aeroplanes, the yarn can also power a spinning motor.
Professor Ray Baughman at the University of Texas at Dallas said: "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."
Prof Baughman prioritised their simplicity as effective for 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."
Results of tests of the artificial muscle appear today in the journal Science. They showed that muscle contraction occurred incredibly fast, taking just 25 thousandths of a second.
The power-to-weight ratio demonstrates the muscles are also four times more efficient than an internal combustion engine. They were also capable of operating at temperatures over 1,000°C, a heat higher than steel’s melting point.
Prof Baughman has said that the application might be incorporated into a “smart” suit for fire-fighters. The clothing material would be designed to react to dangerous temperatures to provide extra protection when needed, due to the intelligence of the material functionality, which Prof Baughman said was “very important”.
He added: "The remarkable performance of our yarn muscle and our present ability to fabricate kilometre-length yarns suggest the feasibility of early commercialisation as small actuators comprising centimetre-scale yarn length."
The difficulty is in “upscaling” the single-yarn actuators to larger actuators where hundreds or thousands of individual yarn muscles operate in parallel.