Overcoming a problem that plagued earlier versions, German researchers have built more efficient metal muscles that could be used for robotic limbs.



Metal muscles made from alloys that change shape when heated first drew attention several years ago when researchers developed a nickel and titanium strip that moved in response to electrical stimulation.



However, such metal muscles have had limited efficiency because they require a large electrical current — up to 100 volts — to flex.




Researchers from the Institut fur Nanotechnologie in Duisburg report in the journal Science that they have now built muscles with the same degree of movement as previous versions but without the electrically generated heat.

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