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New gel is stronger than steel
Muscle-flexing robots with superhuman strength could become a reality thanks to a new expanding material that is stronger than steel.
Scientists have created a gel that acts like muscle when charged with electricity but is far more powerful.
The "aerogel" is almost as light as air, as stretchy as rubber, and stiffer than steel by weight.
Made with ribbons of carbon "nanotubes" - tiny hollow tubes of carbon - the material can expand to 220% of its original length or width in milliseconds when electrically charged.
The gel sheets are capable of handling dozens of times more stress than natural skeletal muscle, say researchers reporting on the technology in the journal Science. Once "flexed", the material can be "frozen" in place.
The US researchers, led by Dr Ray Baughman, from the University of Texas at Dallas, wrote: "These solid-state fabricated sheets are ... rubbers having gas-like density and specific strength in one direction higher than those of steel plate."
Canadian engineer Dr John Madden, from the University of British Columbia in Vancouver, said the material combined the properties of diamonds and rubber.
Currently the ribbons are very stiff in their "stretch" direction but their "transverse" strength is up to a million times weaker.
This ruled out applications requiring "large displacement and any appreciable force". But Dr Madden said the problem might be solved by increasing the ribbon density and interconnections between adjacent fibres.
Writing in Science, he added: "When forces are increased, the ribbon artificial muscles will become candidates for use in medical devices, robots, and perhaps even implants."