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.
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.
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.
Did you see the temperatures? Unless you're worried about hysteresis you should give shape-memory wire (e.g. nitinol) a try. I've got some .004" (100-micron) nitinol wire that can lift 100 grams.
I thought shape memory wire was very expensive though - a few thousadn $/kg? Though checking nitinol.com, it's certainly cheap enough to experiment with - thanks for the tip.
How durable are these synthetic muscles? (i.e. how many contractions?) Anytime I've dealt with twisted or tangled fishing line it seems like the strength is severely compromised.
But not a good reason. Originally it was the boiler time-to-steam; but with a coil that's subsecond. We should really be using steam for lots of things.
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.
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 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.
Wire with current is awesome at warming stuff. Not so good at cooling. By redirecting the fluid or gas from warm and cool reservoires you could rapidly warm/cool the muscle. Even with whole bunch of muscles.
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.
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!
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.
Lifting cars is often an exaggeration in terms of wording, the reality is usually lifting up one side of the car, which is very different in terms of weight.
no safety governor, just fine motor skills by addressing small specific muscle groups, hence unfortunate 'retard strength' myth (trading fine motor skills for blunt force)
The Golgi tendon reflex operates as a protective feedback mechanism to control the tension of an active muscle by causing relaxation before the tendon tension becomes high enough to cause damage.
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.
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.
Muscle is not the only tissue involved with moving a weight around. Obviously you need a skeleton that can bear the load, and a heart & lungs fit enough to pump adequately oxygenated blood. But don't underestimate the large role a strength-adapted central nervous system plays.
I'd give up growing and self-healing if it meant not having to constantly lift to maintain condition and being able to swap out for a replacement in 5 minutes rather than spending weeks or months crippled while waiting for a self-heal.
We aren't there yet either, but when judging practicality you have to include biology's failings alongside its strengths :)
"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.
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...
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.
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.
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.)
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.
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.
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.
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...
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.
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.
66 comments
[ 662 ms ] story [ 351 ms ] threadThe 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.
Doesn't say what kind of "reuse" they are counting.
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.
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.
Are there any applications for this? We can already do the same using pulleys. right?
Awesome, this looks like it can be done at home.
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.
Lifting cars is often an exaggeration in terms of wording, the reality is usually lifting up one side of the car, which is very different in terms of weight.
I'm pretty sure the safeguard here is the Golgi tendon organ
http://en.wikipedia.org/wiki/Golgi_tendon_organ
http://en.wikipedia.org/wiki/Golgi_tendon_reflex
The Golgi tendon reflex operates as a protective feedback mechanism to control the tension of an active muscle by causing relaxation before the tendon tension becomes high enough to cause damage.
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.
The flip side of having crappier levers for force, is that we have better levers for precision.
We aren't there yet either, but when judging practicality you have to include biology's failings alongside its strengths :)
(PDF) http://www.dexmart.eu/fileadmin/dexmart/public_website/downl...
http://books.google.com/books?id=cDx8_ug_GGgC&pg=PA95&dq=twi...
http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=569572...
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.
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.)
https://www.youtube.com/watch?v=f3t2_AX8HUk
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.
Looks like it got everything.
I love how the video shows you how to both make the muscle fiber as well as shows it working under load.
"Synthetic airplane made from black box material 1000 times more heat resistant than the real thing."
I'm okay with that, mind you. THE BRIGHTEST SMILE
For teeth, you want nephrite as the base with a thin shell of corundum on the surface.