Researchers Create Ultrastretchable Wires Using Liquid Metal 94
hypnosec writes "By using liquid metal researchers have created wires that can stretch up to eight times their original length while retaining their conduction properties. Scientists over at North Carolina State University made the stretchable wires by filling in a tube made out of an extremely elastic polymer with gallium and an indium liquid metal alloy."
Are they worried about leaks? (Score:3)
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Researchers [...] have stressed that work needs to be done to address one critical aspect of the wire though – leakage of liquid metal in case the wire is severed.
Re:Are they worried about leaks? (Score:5, Informative)
Wikipedia on Gallium [wikipedia.org]
Pure indium in metal form is considered nontoxic by most sources.
Wikipedia on Indium [wikipedia.org]
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i would imagine airlines would frown upon gallium anywhere near their aircraft through.
Re:Are they worried about leaks? (Score:4, Informative)
metallic gallium is not considered toxic
Wikipedia on Gallium [wikipedia.org]
Pure indium in metal form is considered nontoxic by most sources.
Wikipedia on Indium [wikipedia.org]
Yes, but if it ever leaks out, Gallium might cause structural failure of anything that's made of aluminium. And certainly I don't want to have conductive liquid in my electronic devices, when the cable breaks.
Re:Are they worried about leaks? (Score:5, Informative)
When they ditched mercury thermometers due to toxicity / envrionmental hazards, the replacement is galinstan - gallium, indium, and tin. So it is considerably less toxic.
Unfortunately it wets to glass, unlike mercury which beads up, and is more expensive.
The way around that is to coat the glass with something - I don't recall what now, but I think it was some gallium compound.
On the more expensive front - I'd think both gallium and indium are a couple orders of magnitude more expensive than copper, so don't count on that going away any time soon. (Not to mention copper itself is 'expensive' [~$5/kg, it varies], and manufacturers are cheaping out on it. 12 AWG booster cables?! What kind of sick joke is that?)
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I believe that coating is gallium oxide.
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Arnold won't be happy (Score:4, Funny)
Add campaign... (Score:3, Funny)
John Connor: These wires are made of what?
The Terminator: A mimetic poly-alloy.
John Connor: What the Hell does that mean?
The Terminator: Liquid metal.
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It seems we skipped the sentient AI and killer robots.
Like that's a bad thing?
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No we didn't.
We just launched SkyNet into orbit. We have teams working on autonomous robots with the ability to identify and kill human targets. We have other teams working on making better CPU's, image processing, faster wireless networking, better materials for constructing robots, as well as ongoing creation and testing of new and improved weapons on humans.
Things are progressing on schedule. We appreciate your cooperation.
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http://en.wikipedia.org/wiki/Oerlikon_35_mm_tw [wikipedia.org]
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You mean like the robotic weapon
What makes that a robot?
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The cross section changes (Score:1)
Re:The cross section changes (Score:4, Interesting)
so shouldn't this alter the conductivity of the 'wire'? http://en.wikipedia.org/wiki/Electrical_resistance_and_conductance#Relation_to_resistivity_and_conductivity [wikipedia.org]
One would think so.
But you could design for that, simply by using the smallest diameter as your critical dimension when selecting wire size.
Of course it also allows for some new circuit elements, those that can measure stretch via voltage drop, which might be very useful in robotics or prosthetics.
In short it might not be as much of a detriment as it is an advantage.
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My first idea was a silver surfer brand condom with girth gauge!
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Of course it also allows for some new circuit elements.
Could be an interesting way to improve some variable/tunable elements that currently suffer from issues with contact wear or reliability issues. I'll bet designs even exist already, but have since become environmentally impractical due to being based on mercury.
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That does not address the fact that the summary states that conductivity does not change as the wire is stretched.
The summary states no such thing.
It states that conductivity reduction changes are offset by other changes that reduce resistance.
However that offset is limited to a very small range of current and voltage. Mostly it works for voltage and amperage that would be
found in signaling, not power transmission.
One can not negate the basic laws of electrical transmission that huge amperage can not be carried on tiny wires.
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while retaining their conduction properties
I suppose there is room for various interpretations here.
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unless the stretching of the wire alters the cross sectional conductivity
In a good way, balancing diameter (Score:3, Informative)
Re:In a good way, balancing diameter (Score:4, Informative)
"From TFA, the changing cross srction reduces resistance as it stretches. ... they could be designed for no change when stretched"
Well, that's not quite what TFA writes: "As expected, electrical measurements show that the fibers increase resistance as the fiber elongates and the cross sectional area narrows. Fibers with large diameters (~600 [micrometers]) change from a triangular to a more circular cross-section during stretching, which has the appeal of lowering the resistance below that predicted by theory."
The abstract doesn't mention how the circular/triangular transition would affect the resistance - with conservation of volume it shouldn't matter. But I don't read here in any way that this effect would be able to cancel the resistance increase due to stretching.
Note that in first approximation, resistance would scale as L^2 for a wire with length L (both diameter decrease and length increase affect the resistance). With stretching up to a factor 10, i.e. 100x increase in resistance, a small effect due to the shape of the cross section would be negligible.
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Yes, and the resulting change in resistance in this kind of liquid-metal wire has been used for years in the medical field for 3 decades:
http://www.adinstruments.com/solutions/research/applications/strain-gauge-plethysmography
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Coming soon... (Score:5, Funny)
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well, vaccuum tubes *are* making a come-back. at least in terms of snootyphile audio systems.
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Vaccuum tubes never went away for guitarists, because overdriven transistors distort differently than overdriven tubes. Many guitar players will have a small tube amp with a microphone in front of it feeding a solid state amp -- the tube amp is for distortion, the solod state amp for amplification.
If you look at it on an oscilloscope, when driven to distortion levels ("clipping") the transistors will produce square waves that are actually square, while the tube amp's waves are rounded at the corners and fla
I don't get it. (Score:1)
What is the practical application of being able to freely apply even more jack/plug torsion exactly?
Today's news at 5 (Score:2, Funny)
Re:Today's news at 5 (Score:4, Informative)
Good thing Indium and Gallium aren't toxic or heavy metals then eh
Re: Today's news at 5 (Score:3, Funny)
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yes, yes you can.
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The tube would likely kink quite easily, squeezing out the liquid from the middle - thus stopping the electron flow - or reducing the diameter so much as to greatly alter the resistance of the wire. Something like this image: http://hostedmedia.reimanpub.com/TFH/Step-By-Step/FH10SEP_BUYHOS_01.jpg [reimanpub.com].
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If the tube is crushed flat there would be no liquid metal there for the electrons to flow through. Sorry but electrons flow from atom to atom. If the pinch is wide enough the electrons will not be able to jump the gap. The electron flow needs a continuous conductor. if the pinch creates a gap of 1/4 of a mm in the liquid the flow of electrons will be stopped.
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As you approach that pinching point the increased resistance creates heat, you'd likely melt the wire if you pinched it down and it didn't stop the electron flow. Imagine the melted wire ends leaking electrically conductive puddles that then have hundreds of tiny contact points, not to mention ground. Could be very dangerous -- The wire busts and electrocutes people. Also, too many electrons flowing in too small a wire (or even between two small a path between conductive puddles) are how electrical fir
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Melting would only occur if there was enough power in the wire to create the heat. Headphone work at low voltage and low amperage. The most powerful headphones I found were 200mW. That is far from enough power to melt plastic. Sure if it was being used for household current it might occur but that is not what this device is designed for.
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First of all, I don't think you appreciate how tiny that gap would have to be.
Second of all, to even started to approach that requisite size would require *FAR* more work than pinching it with your fingers, or even folding it in half like a tube. You'd need many times more force, and more than likely that amount of pinching force would end up cutting the wire completely long before it would simply halt the electron flow with the insulation intact (unless the insulation itself were as ductile as, say...
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The point you miss is that electrons do not flow through air very well; that would be called a spark. The sides of the tube do not have to be close enough to cut off the flow of electrons; it just has to be small enough to separate the liquid conductor. If there is a gap in the conductor there will be no electron flow.
As for melting the insulation, that would require a lot of power to push the electrons against the resistance to create enough heat. Most headphones do not have enough power to do that as elec
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Which I am asserting that no normal amount of pressure could hope to achieve without actually breaking the wire in the first place.
Yes, I looked at the picture of the hose... but we're not talking about stopping liquid flow, we're talking about stopping electron flow.
Enough to stop the liquid from flowing through the gap, yes... not enough to stop it fro
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Which I am asserting that no normal amount of pressure could hope to achieve without actually breaking the wire in the first place.
A plastic tube that is malleable enough to stretch 8 times its length is malleable enough to be crushed flat without "breaking". Take some rubber tubing, fill it with water and crimp it like the picture. That is exactly what this device is. It is not a wire with a solid core; the core is liquid and will move out of the way of a crimp.
Enough to stop the liquid from flowing through the gap, yes
This shows how little you understand the concept. The liquid does not flow at all. The electrons cascade through the liquid. Where there is no liquid, as in a pinch, there is n
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Half right. Where there is no liquid there is no electron flow. However, your faulty assumption is assuming that there wouldn't be any of the conductor inside a pinched area.
There's a handful of reasons why this is so, not the least of which is the fact that this isn't like a hose where the liquid you displace by pinching can flow out of either end... it's a flexible container, but it's closed on either end... and it's also *FILLED* with
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There's a handful of reasons why this is so, not the least of which is the fact that this isn't like a hose where the liquid you displace by pinching can flow out of either end... it's a flexible container, but it's closed on either end.
Yes it is but it is also a flexible container that can change it cross section. If you press one part of the tube another part of the tube can balloon out and accommodate the liquid.
The amount that the wire would have to stretch to be pinched to such thinness to make room for all of the displaced liquid would, again, tear apart the wire itself unless it were made out of an abnormally ductile substance (which rubber is not).
The tube is very ductile. It can elongate 8 times it's original length. Say one has a 5" long wire and 1/2" is pinched flat. The rest of the wire would have to accommodate .5/59.9= 8% more liquid. That would mean that the rest of the wire would have to increase its diameter by 1.6%. That would not be difficult for a material t
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When it is free to do so, yes... if you are pinching it, then it *ISN'T* free to elongate along the region that you are pinching it. The result is a shearing force that will almost certainly sever it just as certainly as scissors would.
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if you are pinching it, then it *ISN'T* free to elongate along the region that you are pinching it.
So what? My point is that if it can elongate it can also bulge and the liquid displaces from the pinch will be accommodation by deforming the rest of the tube.
The result is a shearing force that will almost certainly sever it just as certainly as scissors would.
Yes scissors would be a shearing force but what I am talking about is a crushing force. Take the tube, put it into a C clamp and tighten. The tube will collapse long before it cuts. That is a crushing force. You really need to learn some physics. A shearing force is high pressure over a very narrow area. A crushing force is also high pressure but over
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The cross section reduces because the fluid has a place to go in the longer tube. If one pushed the fluid up to one end of the tube the cross section would get bigger and the wall thickness thinner.
Take a long thin balloon and fill it with water. Hold both ends and pull. It will elongate. Grab the middle and squeeze. The ends will bulge which will accommodate the liquid. There is no magic about it. It is simple elastic physics. Anything that can elongate can also bulge.
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It is simple. the section one is not pinching will expand to accommodate the liquid. The liquid from the area being pinched goes into the area not being pinched which bulges to accommodate the liquid. It is called elasticity. Whether it is lengthened or not is irrelevant. The fact is that if the tube can lengthen means it can also bulge. You can't constrain an elastic material to only lengthen in one direction. If the tube can lengthen it can also increase circumference. The tube can increase circumference
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No... not at all. It *CAN*, but that is not the same thing as meaning that it would. And in fact, for something like wire insulation, it probably *wouldn't*, because taking a vertically running wire, for instance, the ability it to bulge would cause it to bulge out at the bottom end of the wire, leaving relatively little conductive liquid near the top, and creating an inconsistent conductivity across the wire.
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If you are such a materials expert how can one allow the tube to elongate but constrain it from bulging? You can't. The scenario you propose is only a problem it it bulged easily like a latex balloon. It is not a problem if it takes a reasonable amount of pressure to bulge. The couple of ounces of liquid metal in a tube will create a few psi in the bottom end of a vertical wire. Now say you put 30PSI on a small section of the wire. That small section will flatten and the rest will bulge slightly. Look at th
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First of all, try the following experiment: Since you evidently have silicone tubes to work with, take an 18" long or so silicone tube, and completely fill it with water completely seal both sides, and making sure that there is no air inside the tube. Once you've done this, you will note that the pressure required to flatten it with liquid inside is *DRASTICALLY* larger than it is when it is just air... or even if the liquid inside has someplace else to go, such as what you get with a hose that is exper
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Sorry but you are a moron.
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I've attempted to describe to you what would happen at the very tiny scales that would be easily wide enough for electrons to pass, while still being far too tiny for the surface tension of the liquid to permit the formation of droplets that would allow macroscopic flow. Again, everyday experience with the macroscopic, such as what you'd get with a water hose and blocking water by crimping it just doesn't translate very well to scales as small as what you need to actually block electron flow.
However, if
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Perhaps you might want to read a little on how electrical current flows [wikipedia.org]. The crimp does not stop the flow of electrons it separates the conductor so that there is no conductive material for the charge to flow through. Electrons to not flow through air except at very high voltages. Outside of a conductor dielectric breakdown [wikipedia.org] must occur for current to flow.. You keep concentrating on the width of the crimp but ignore the length. If I can create a gap in the conductor fluid 1/2 mm long no matter how thick the
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It's this point that you're wrong about. You'll get an inkling of what I'm talking about if you try the experiment I described with a tube full of water and two sealed ends.
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How does electric charge flow when there is no conductor? If the tube is crimped so that the sides are touching there is no space for the liquid. You stated that yourself. Then you stated that there is enough room for "electrons to flow". If two attoms of the conductive fluid are more that 1/2mm apart the charge will not transfer between them. If a crimp is string enough to stop water at 50 psi it is strong enough to separate conductor under no pressure.
As for your experiment, I do not have the equipment
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The former is caused by electrostatic repulsion between droplets of liquid, whose minimum size is determined by the surface tension properties of the liquid. But even these tiny droplets, which are on the order of only about a nanometer or two in size, are still about another order of magnitude larger than the molecules that liquid itself is made of.
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You don't account for the sutface tension. If you squeeze the tube thin enough, the liquid may gain energy by breaking up.
Think of water running out of a tap. The stream gets thinner and thinner as it falls and then breaks up into separate droplets.
Glad to Hear Researchers... (Score:2)
...are finally finding something besides how to hack into some software.
Isn't this 30 year old technology? (Score:4, Interesting)
This sounds exactly like an indium-gallium strain gauge, which in turn is an evolution of the mercury-in-rubber strain gauge used for at least 30 years in medical measurements. These are rubber tubes filled with liquid metal, just like the "wires" described in this article. Their resistance increases as they are stretched, and they've been used for everything from monitoring respiration (wrapped around the chest) to monitoring blood pressure. A quick search on "Strain Gauge Plethysmography" will produce some relavent pages.
Thus this seems like a just a new use for an old technology. Am I missing something?
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why, so you can fuck up your headphone jack even more?
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So you can say "Get off the cord ; I cant't hear the music"?
What??? (Score:1)
gallium, while not very toxic, has other issues. (Score:2)
http://www.youtube.com/watch?v=JHHI2Lk79cY [youtube.com]
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I know it will be hard, but we'll just have to make sure we don't leave excess amounts of molten gallium on our aluminum based products for prolonged periods of time.
Stevens was right. (Score:2)
Jasper (Score:1)
Hey, I just made stretchable ice!
That's one way to do it. (Score:3)
Wouldn't it be simpler to just take a spring and put an insulating plastic jacket around it? Higher resistance, but no leak hazard, could be cut to length as required, and easily made on existing production lines.
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Metals that make springs make poor conductors. There is also the fact that springs have a stress limit. Pull to hard and they stay straight. For a spring to elongate it takes a large diameter spring relative to the diameter of the wire. The article states 8 times. That means the coil must be at least 2.5 times the diameter of the wire. Factor in double that so that the wire does will return to a coil makes it 5 times. The 1/8" wire would be a coil over 1/2" in diameter. Not so great for portable headphones.
Do you suppose it could form other solid shapes? (Score:1)
Speaker cables (Score:2)
Sounds like a great idea for speaker cables. You can stretch the cable to whatever distance you need!
Is it oxygen-free? I hate how oxygen ruins the timbre of my cables. ;-)
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until it gets squeezed under a chair leg or from pulling it around a corner.
Internet Applications (Score:2)
Finally we can get rid of all that copper wiring and replace it with tubes of liquid metal, as it should have been!