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Is this the robot muscle we’ve been waiting for?

December 1, 2012

Researchers at University of Texas at Dallas have developed a new type of actuator with some pretty amazing properties. These “artificial muscles” are made from carbon nanotubes, twisted into yarn and infused with paraffin wax. The fibers can lift more than 100,000 times their own weight, and generate 85 times more mechanical power than same-sized natural muscle, according to a recent press release.

Lead researcher Ray Baughman says “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.”

The actuators work in a way very similar to air muscles: the carbon nanotubes form a strong, unstretchable outer helix, like a Chinese finger puzzle.  When the material inside expands, the outer helix is forced to shorten, pulling its ends together with a very large amount of force.  With air muscles, the expanding material inside is a bladder pumped with air; the new nanotech muscles instead use paraffin, which expands when heated, and then contracts again when it cools.

Another analogy would be nitinol muscle wire, a nickel-titanium allow that changes shape when heated or cooled.  I’ve worked with that stuff in the past, and found it to be not all it’s cracked up to be; though fairly strong, it tends to be quite slow (especially in the cooling cycle).  It’s possible the new carbon nanotube/paraffin combo will have a similar problem, but the researchers claim otherwise:

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.

Of course that is for individual fibers.  A thick bundle of them could well have heat dissipation problems, which could be a challenge to scaling them up.  Still, these early results seem very encouraging.  Here’s a video from the research team:
Robot enthusiasts have dreamed for years of an actuator as strong, fast, and light as human muscle, and so far, everything has fallen short.  While we can certainly make humanoid robots able to walk, do gymnastics, ride bikes, and even jog with standard electric motors, we would currently be hard-pressed to build something with human performance, to say nothing of superhuman performance.  If these new actuators can be scaled up, they could enable all sorts of new applications, from exoskeletons for the disabled, to giant battle mechs that can run and jump over rugged terrain.

What do you think?  Is this the robot actuator we’ve been waiting for?  Weigh in with your thoughts below.

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  1. Artificial Muscle from Fishing Line | Bot Scene

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