Artificial muscle made of fishing line is 100 times stronger than yours

February 24, 2014

By taking simple sewing thread and fishing wire and giving it a twist, scientists have created artificial muscle that's 100 times stronger than human or animal sinew. The invention, described in the journal Science, could be useful for prosthetic limbs, humanoid robots, implanted medical devices and even wearable clothing.

This wouldn't be the first artificial muscle out there: there are carbon nanotube yarns and metal wires, but they're often expensive or store relatively low amounts of energy compared to their competitors, scientists said.

These new high-strength polymer , made out of cheap, everyday materials that cost about $5 per kilogram, draw their strength from their geometry. In experiments led out of the University of Texas at Dallas in Richardson, scientists took these thin fibers that were just a few hundred micrometers long and twisted them until they began to coil. (You can see this same effect yourself if you take a rubber band and twist it until it starts to collapse into larger loops.)

As it coils, the twisted becomes shorter and thicker, and then the researchers heat-treated it to make it set. The scientists found that if they made the fiber coil in the same direction as the twist, the fiber cable would contract. If the fiber was forced to coil in the opposite direction of its twist, the fiber cable would expand.

When they applied an energy source to the fibers-typically heat-the scientists got different versions of their fibers to contract by 49 percent or to expand by 67 percent. They even produce 7.1 horsepower per kilogram, about the same power as a jet engine (when scaled down for size). And the fibers can last through millions of these cycles, making them very durable, reusable devices.

"Despite their small diameter, the fibers can be indefinitely long and used in large structures," Jinkai Yuan and Philippe Poulin, scientists from the University of Bordeaux in France who were not involved in the paper, wrote in a commentary.

The scientists think this could be useful for a number of applications that need , whether getting the faces of to move with more human-like expressions or getting better muscle. They could be used to automatically open and shut blinds in response to the outside climate. The researchers already have created a textile with pores that expand and contract in response to heat-which could lead the way to adaptable, breathable clothing.

Explore further: Researchers create powerful muscles from fishing line and sewing thread

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3 / 5 (2) Feb 24, 2014
Team them up with a powerful gyro and a small reactor, and we can have 'Mechs.
5 / 5 (1) Feb 24, 2014
Every other article I've seen about this says they used fishing line. I'm wondering which type of fishing line. The regular old nylon line would lose it's twist stress if they heated to set the coils I believe. It's probably one of the newer types. Could be an interesting project.
5 / 5 (1) Feb 24, 2014
Low temp conversion of heat into mechanical energy. Just have to cycle the heat source exposure and cooling medium (air). Wonder what the contraction and relaxation timing relationships are given certain temps as well as amount of heat converted into mechanical energy.

"It's...It', it's green"
not rated yet Feb 25, 2014
With actuator efficiency of 1.7% these things aren't going to be used for anything except novelty purposes like opening and closing window blinds.

The problem is that you have to heat the material up for anything to happen, and as it's specific heat capacity is fairly large, you're spending loads of energy to change the temperature of the fibers, and then dumping that energy out for the opposite stroke.

So while you could make a moped run on a kilogram of this material, you actually need a 400 HP sports-car worth of fuel to power it.

not rated yet Feb 25, 2014
With actuator efficiency of 1.7% these things aren't going to be used for anything except novelty purposes like opening and closing window blinds.

From the article:
Per weight, they can generate 7.1 horsepower per kilogram, about the same mechanical power as a jet engine.

Compared to natural muscles, which contract by only about 20 percent, these new muscles can contract by about 50 percent of their length.

the muscles can be self-powered by environmental temperature changes

I don't know where you're getting your 1.7% figure from, or needing vast amounts of fuel to use the polymers.
not rated yet Feb 27, 2014
I don't know where you're getting your 1.7% figure from, or needing vast amounts of fuel to use the polymerss

Shape memory alloys and polymers are generally very inefficient because of the reasons I outlined: the actuation happens in respect to temperature change, and to change the temperature you need to add heat. The specific heat capacity of nylon for example is 1700 Joules per Kelvin per Kilogram.

In other words, to raise the temperature by 1 Kelvin in 1 seconds you need 1.7 Kilowatts of power. If you need to heat a 1 kilogram actuator from 20 C to 70 C and back at a rate of 5 Hz, you need to add 425,000 Joules per second, or 425 kW, or 582.3 HP

With a mechanical power output of 5.2 kW that represents an efficiency of approximately 1.2% from heat to work.

These are just ballpark figures, but that's about what it can do.
5 / 5 (1) Feb 27, 2014
However, I suspect there might be an upside to the story, because generally speaking materials that act like springs cool down when stretched and heat up when compressed. If you took a bunch of these strings and pulled on them, then release the tension, it could make a fairly efficient heat pump.

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