
Synthetic Muscle Made of Fishing Line is 100 Times Stronger Than the Real Thing - adventured
http://www.popularmechanics.com/science/health/breakthroughs/synthetic-muscle-made-of-fishing-line-is-100-times-stronger-than-the-real-thing-16514805
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anigbrowl
The paper is behind a paywall, but having read the methods and materials, this
is a Very Big Deal. The amterials are cheap, the fabrication techniques are
low tech enough that you can do it at home with basic tools, and the pwoer
delivery is ridiculous. They've demonstrated it working with multi-kilogram
weights. I'm going to buy some fishing line.

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philwelch
Fishing line is designed for hauling up hundreds of pounds of fish when being
cranked up with a human-powered reel. It's not surprising that it can be
applied in this fashion.

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arnarbi
If "strength" meant tensile strength, this would not be an article, let alone
a paper.

The fact that fishing line can be applied this simply to create a "muscle"
that forcefully contracts (that's what they mean by "strength" here) - then
this is certainly both surprising and remarkable.

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quarterwave
Human muscle also stores energy in the form of glycogen, so it's got batteries
included. The approx 25% energy efficiency of the human muscle is limited
mostly by the 40% efficiency of burning glucose into ATP molecules. The
article mentions 'relative inefficiency' of the new muscle - a quick search
indicates it's around 1%. My respect for human muscles has increased!

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davyjones
Human muscles are capable of much...(comparable to chimpanzees?). But there is
some sort of a governor in place to ensure safety. In extreme circumstances,
the governor can be "turned off" (adrenalin?) and we have cases of mothers
lifting cars to save her child, etc.

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Symmetry
Essentially. IIRC there are a couple of negative feedback loops, one local and
one involving the brain, and they usually limit you to about a 1/3 duty cycle
for each muscle fiber. There are certainly ways that ratio can be increased,
just yelling can increase the maximum force you can consciously exert by about
15%. I have no idea what the maximum is, but I'd imagine that going much
further than what you're normally limited to drastically increases your odds
of tearing something during exertion.

The reason chimpanzees can exert more force is anchoring, their muscles are
anchored to the bone further form the joint so they have better mechanical
advantage. A human has a much wider range of movement, though, and I believe
we better maintain force under movement. So which a chimp might be able to
lift themselves more easily, a human ends up being able to throw a rock or
spear much further.

EDIT: Also, ekianjo is right that lifting cars is an exaggeration.

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icegreentea
It's probably best not to compare human and chimp ROM, since that has less to
do with muscle attachment sites, and isn't really that consistent, joint to
joint. For example, a chimp shoulder has fabulous overhead ROM... as expected
for a tree climber and swinger.

The flip side of having crappier levers for force, is that we have better
levers for precision.

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beambot
These have been known for some time; just search for "twisted string
actuator". I recall doing a literature survey to see how far back the idea
went... Here are a few links...

(PDF)
[http://www.dexmart.eu/fileadmin/dexmart/public_website/downl...](http://www.dexmart.eu/fileadmin/dexmart/public_website/downloads/presentations/USAAR-
Workshop-A3.pdf)

[http://books.google.com/books?id=cDx8_ug_GGgC&pg=PA95&dq=twi...](http://books.google.com/books?id=cDx8_ug_GGgC&pg=PA95&dq=twisted+string+actuator&hl=en&ei=5-sDTovDOJP3gAeuyfTjDQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CC8Q6AEwAQ#v=onepage&q=twisted%20string%20actuator&f=false)

[http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=569572...](http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5695720&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D5695720)

There are patents dating back to the 1930s, 1970s, and 1980s. In recent years,
this is (again) being actively explored by roboticists.

EDIT: My bad! The twisted actuators in this work are using heat (and
potentially light / electricity) to expand and contract, not the actually
twisting motion.

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scriptproof
I believe you have not read the article entirely. The principle is not to
twist the line to contract the muscle, that is made with an actuator, the
principle is to apply a current to a mechanically twisted fiber to contract it
and produce a movement.

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beambot
My mistake! From the PM article: "Also, by blending in conductive wire or
wrapping the muscle with a light-absorbing coating, the researchers can
control the muscles' movements with electricity and light instead of direct
heat."

So these are heat-driven actuators (and potentially electricity or light
driven). Very cool! Thanks for the clarification. (Also, this isn't at all
evident from the Science abstract. I will read full paper tomorrow when I can
pierce the paywall.)

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tlarkworthy
Not mentioned in the article but highlighted in the paper is that this
actuator has no hysteresis. If you have played with shape memory alloy, you
will know the non-linearities in it are extremely hard to perform control
with. So this is a big advantage of this actuator over SMA wire for control.

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runewell
Can this be used in robotics? I know the air-compression muscles provide some
of the best performance for grip and human-like motion but they require noisy
heavy equipment and can be costly. Although this solution looks more primitive
it makes me wonder if it could be engineered into an effective replacement at
a much lower cost and weight along with silence when in operation.

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XorNot
Heat controlled, so you'd need a central heating and cooling reservoir to
achieve motion with any rapidity.

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bane
So now the entire field of artificial muscles is going to change to find
materials that do something like this, but better.

I love how the video shows you how to both make the muscle fiber as well as
shows it working under load.

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shearnie
I wonder what is the potnetial of how quickly it could contract?

If not so fast, but incredibly strong, then I assume you could set it up with
cranks and high gearing to make an engine. Like pedaling a push bike with your
legs.

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graeham
They did some tests at 1Hz for >1M cycles.

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daralthus
Somebody who read the paper, can you tell us how much was the achieved length
change? It doesn't seem that much in the video.

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graeham
49%, from the abstract, although this is an extreme in their results.

Quite an impressive application actually. It has quick actuation, large force
generation, and large displacements. Typically these "muscle replacements" are
lacking in at least one of these and thus make them impractical outside the
lab.

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tomp
Wow, that actually makes it useful, unlike what was shown on the video.

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Bpat
Run some nichrome wire up the center of the coil and you could heat it really
quickly.

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scotty79
I was thinking rather, put it in an ellastic tube and pass warm/cool liquid or
air through it.

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Sharlin
Pumping electrons vs. pumping (and heating) a fluid? There's a reason we don't
use steam engines anymore :)

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jjoonathan
There's also a reason why we don't use Peltier pumps in refrigerators.
Electrons are great at heating things, not so great at cooling them off.

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a-priori
In this case, that would mean that it would be fast to contract but slow to
release. Our muscles have a similar problem, though maybe not quite as bad.

This is part of the reason our muscles work in antagonistic pairs, e.g. the
biceps and triceps, where a joint moves based on the relative tension of the
flexor and extensor muscles.

You would probably want to do a similar arrangement with these coils.

~~~
icegreentea
Yeah, but should probably point out the relative time scales involved. In
muscle, once the nerve impulse is off, in a non-pathological state, muscle
tension in the motor unit will drop to zero within hundreds of ms. For example
[http://www.bem.fi/book/21/fi/2108.gif](http://www.bem.fi/book/21/fi/2108.gif)
shows a typical force-time curve for an impulse.

I have no idea what the equivalent would look like in this case, but I imagine
in a purely passive cooling solution, it'd have quite a long time constant.

I don't have the paper, and in the abstract they awkwardly compare the
strength to human muscle length and weight, when typically, its muscle cross
section that bounds a particular muscles strength. This is important because
if you start stacking these fibers in parallel to get more strength, then you
pretty much dictate some sort of active cooling system to maintain any type of
performance and control.

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x0054
This has been discussed on the Slingshot Chanel. I am surprised that this has
not been explored more until now.

[https://www.youtube.com/watch?v=f3t2_AX8HUk](https://www.youtube.com/watch?v=f3t2_AX8HUk)

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jrockway
"Synthetic teeth made from diamonds 1000 times stronger than the real thing."

"Synthetic airplane made from black box material 1000 times more heat
resistant than the real thing."

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pavel_lishin
Would there actually be a disadvantage to having diamond teeth? (Aside from
aesthetic issues - I don't want my teeth to literally sparkle.)

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omegaham
One problem is that diamonds are surprisingly brittle. If you tap a diamond
along a cleavage point, it will break. Diamond cutters take advantage of this;
you can break a diamond with a wooden dowel if you hit it in the right place.
I'd be really unhappy if my tooth just split in half because I bit down on
something slightly wrong. Of course, regular teeth do that too...

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mrfusion
Can someone put up instructions for making it?

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ilyasimenko
Video in the article is pretty straightforward. I have tried it myself with
0.35 mm fishing line, but I haven't got a heat gun, and that was a huge
problem. I've tried to heat the coil with lighter, but it's really difficult
to control the temperature. If it's too low, coil does not contract, if too
high - melts immediately. But one of about ten attempts was successful, so it
definitely could be done at home.

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IgorPartola
Do you have a hair dryer? If you can actually use a cheap heat gun, Harbor
Freight Tools sells them really cheap in the US.

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ilyasimenko
Yes, I do. It's not hot enough. Heat guns are also cheap here in Ukraine, may
be I'll buy on occasion.

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DigitalSea
"Bro, do you even lift?" just took on a whole new meaning. This is super cool
though, as the article says, I cannot believe someone hasn't discovered this
sooner. I wonder if we will be seeing military and or medical applications
using similar materials and techniques soon? This could work wonders for
rehabilitation.

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ajcarpy2005
Hydraulics could be another solution but better if the pumps are small and
distributed and more integral to the overall structure than a large pump for
each muscle group.

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ChuckMcM
Pretty cool, much simpler than Nitonal (aka Muscle wire). Sigh, and another
cool thing to build in my "spare" time.

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mdturnerphys
How is it simpler than nitinol?

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ChuckMcM
The lack of hysterisis and creep means that you can drive them with and open
loop drive system. That is a much simpler system to build.

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ajcarpy2005
Why didn't I think of this?

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spiritplumber
The best inventions leave you thinking "Why didn't I do this?"

Awesome, this looks like it can be done at home.

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huherto
Looks cool!

Are there any applications for this? We can already do the same using pulleys.
right?

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mhb
What is the activation temperature (range)?

