Robotic Muscles from Fishing Line and Nichrome

Did you know that under the right conditions, nylon can be used as a type of artificial muscle? We certainly didn’t until we came across [Brandon T. Wood]’s Material Linear-Actuator for Robotics entry for the 2018 Hackaday Prize.

When [Brandon] first learned about Nylon Linear Material Actuators (NLMAs), he became determined to find a repeatable and practical method of making and experimenting with them. This is how it works: hyper-wound coils of nylon, when heated, will contract along their length while expanding in width. Upon cooling, they return to their original shape.

[Brandon] has been busy mainly with the kind of work that is important but not very flashy: finding accessible methods to reliably create strands of artificial nylon muscles cheaply and reliably. His current method uses a jig to wind nylon fishing line until it coils upon itself tightly, then twist a length of nichrome wire around the outside to act as a heater. Using this method, the coils can be electrically controlled. [Brandon] is currently experimenting with creating bundles of individual nylon coils to act all together as one big muscle, because while one wire isn’t particularly strong, a bundle could be quite another story. It’s definitely unusual and is doing a lot of work to turn a known phenomenon into something hackable, which makes it lovely to see in this year’s Hackaday Prize.

19 thoughts on “Robotic Muscles from Fishing Line and Nichrome

  1. “Did you know that under the right conditions, nylon can be used as a type of artificial muscle?”

    Yup! I seem to remember an article by someone who supposedly “discovered” this effect and a lot of people making a big deal that suddenly “muscle wires” were cheap enough for hackers to use in their robotics projects. Then there was a whole lot of “me too” articles where people made use of and worked towards perfecting this technique.

    I thought I saw that here at HaD! Though.. it was so long ago… maybe it was just something linked to on Slashdot. For some idea how long ago that was… I’m not sure but I think it was the opening of the RepRap project and the completion of the first Darwin that finally knocked this one down from big news to old news.

      1. You’re right, that’s exactly the same! So “we” did know about earlier, oops.
        The work [Brandon] is doing on this particular project also isn’t about re-inventing the nylon muscle part, it’s about finding ways to make them electrically (and hopefully reliably) controlled by integrating nichrome wire into the windings to control the heating. It’s certainly economical; hope the performance is there, too.

    1. My son and his team built a machine similar to that for their senior electrical engineering project. It would push out the nylon string and then twist it at a specific rate while heating to automate making muscle wire.

  2. If I may ask, I have a project I have been planning for a year now, it includes two 5-foot long arms that can extend and retract with movable joints and fingers, the character reference is Roger the Janitor from Little Nightmares, a game from Tarsier Studios. I have needed assistance on material ideas for the arms to look as realistic yet fluid as possible.

  3. Don’t use Nitinol or the fishing line artificial muscles for robotics in exoskeletons. I already did it. Nitinol works but it is extremely power inefficient.
    My Nitinol Exoskeltons and Levers Videos:






    Sorry about no videos on the fishing line artificial muscles. Don’t use if for exoskeletons because it is worse to use than the Nitinol for levers that go back and forth.
    By Sean Benson.

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