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Researchers Create Ultrastretchable Wires Using Liquid Metal

samzenpus posted about 2 years ago | from the keep-it-stretching dept.

Science 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."

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Are they worried about leaks? (2)

fotoguzzi (230256) | about 2 years ago | (#42343873)

Just asking.

Re:Are they worried about leaks? (2, Informative)

Anonymous Coward | about 2 years ago | (#42343947)

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? (5, Informative)

Anonymous Coward | about 2 years ago | (#42344197)

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]

Re:Are they worried about leaks? (2, Informative)

Anonymous Coward | about 2 years ago | (#42344421)

i would imagine airlines would frown upon gallium anywhere near their aircraft through.

Re:Are they worried about leaks? (3, Informative)

fufufang (2603203) | about 2 years ago | (#42344891)

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? (0)

Anonymous Coward | about 2 years ago | (#42344237)

MSDS show handle with care and not dangerous
Material Safety Data Sheet [mcp-group.com]

Re:Are they worried about leaks? (4, Informative)

mirix (1649853) | about 2 years ago | (#42344839)

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?)

Re:Are they worried about leaks? (1)

Skapare (16644) | about 2 years ago | (#42345157)

I believe that coating is gallium oxide.

Re:Are they worried about leaks? (0)

Anonymous Coward | about 2 years ago | (#42345495)

12 AWG booster cables?! What kind of sick joke is that?

Electric space heaters, with power cords that melt during continuous use. At least a car fire might happen outdoors, some of the time.

If you use a 120V 60Hz space heater rated for more than 900W, and the cord isn't as thick as your thumb or shorter than 4 feet, then don't run it continuously.

Re:Are they worried about leaks? (2)

tofarr (2467788) | about 2 years ago | (#42346059)

Also copper thieves would have a field day - no need to haul anything away - just cut the cable near the bottom and watch the metal flow into a bucket

Arnold won't be happy (3, Funny)

Metabolife (961249) | about 2 years ago | (#42343881)

Here comes the upgrade.

Add campaign... (3, Funny)

The Grim Reefer (1162755) | about 2 years ago | (#42343883)

I can see it now.

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.

Re:Add campaign... (1)

Jetra (2622687) | about 2 years ago | (#42344031)

It seems we skipped the sentient AI and killer robots.

Re:Add campaign... (1)

The Grim Reefer (1162755) | about 2 years ago | (#42344261)

It seems we skipped the sentient AI and killer robots.

Like that's a bad thing?

Re:Add campaign... (3)

davester666 (731373) | about 2 years ago | (#42344371)

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.

Re:Add campaign... (1)

Sussurros (2457406) | about 2 years ago | (#42344841)

You mean like the robotic weapon that killed nine people and wounded 14 in October 2007? That was only news because it killed the wrong people. Bad Robot! Bad Robot! Unlike the Obama administration that targets rescuers at sites of drone missile strikes and mourners at the funerals of its victims. US military parlance for this double tapping. Bad President! Bad Policy! But not news because it's killing the right people, the innocent that live with the guilty.

http://en.wikipedia.org/wiki/Oerlikon_35_mm_twin_cannon [wikipedia.org]

Re:Add campaign... (1)

wonkey_monkey (2592601) | about 2 years ago | (#42345847)

You mean like the robotic weapon

What makes that a robot?

Re:Add campaign... (1)

Jetra (2622687) | about 2 years ago | (#42347759)

Is that supposed to be a reference to Eagle Eye? That was just a movie.

Re:Add campaign... (1)

I Mean, What (2778851) | about 2 years ago | (#42350785)

No, I think he means the human-recognition sentry turrets in S. Korea.

The cross section changes (1)

bigkahunah (1093791) | about 2 years ago | (#42344013)

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]

Re:The cross section changes (3, Interesting)

icebike (68054) | about 2 years ago | (#42344159)

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.

Re:The cross section changes (0)

Anonymous Coward | about 2 years ago | (#42344269)

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.

So in short, it might not be all that useful as a conductive pathway, but extremely useful for other purposes, like sensors.

Re:The cross section changes (1)

F34nor (321515) | about 2 years ago | (#42344689)

My first idea was a silver surfer brand condom with girth gauge!

Re:The cross section changes (0)

Anonymous Coward | about 2 years ago | (#42345601)

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.

We already have those. They're called strain gauges.

Re:The cross section changes (1)

Guppy (12314) | about 2 years ago | (#42346837)

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.

Re:The cross section changes (1)

bigkahunah (1093791) | about 2 years ago | (#42352457)

That does not address the fact that the summary states that conductivity does not change as the wire is stretched.

Re:The cross section changes (1)

icebike (68054) | about 2 years ago | (#42352723)

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.

Re:The cross section changes (1)

bigkahunah (1093791) | about 2 years ago | (#42353393)

while retaining their conduction properties

I suppose there is room for various interpretations here.

Re:The cross section changes (1)

viperidaenz (2515578) | about 2 years ago | (#42344165)

unless the stretching of the wire alters the cross sectional conductivity

In a good way, balancing diameter (2, Informative)

raymorris (2726007) | about 2 years ago | (#42344217)

From TFA, the changing cross srction reduces resistance as it stretches. At the same time, stretching increases resistance due to reduced diameter. The two effects tend to cancel one either, so they could be designed for no change when stretched, if it mattered to the application. In 99% of cases, it doesn't matter. You simply want "low resistance" and don't care if it's 0.012 ohm or 0.015 ohm.

Re:In a good way, balancing diameter (0)

Anonymous Coward | about 2 years ago | (#42344717)

Say what? From the abstract in the article:

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.

Re:In a good way, balancing diameter (0)

Anonymous Coward | about 2 years ago | (#42344855)

!!!! HUMBUG... reducing diameter/cross section increases resistance. increasing length increases resistance.

Re:In a good way, balancing diameter (3, Informative)

hankwang (413283) | about 2 years ago | (#42345343)

"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.

Re:The cross section changes (1)

Anonymous Coward | about 2 years ago | (#42344283)

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

Re:The cross section changes (1)

partyguerrilla (1597357) | about 2 years ago | (#42344321)

It's all in the game, yo.

Coming soon... (5, Funny)

SwampChicken (1383905) | about 2 years ago | (#42344093)

...to a manufacturer near you. Spaghetti wiring to complement their existing spaghetti code.

Re:Coming soon... (1)

TheGratefulNet (143330) | about 2 years ago | (#42344473)

well, vaccuum tubes *are* making a come-back. at least in terms of snootyphile audio systems.

Re:Coming soon... (1)

mcgrew (92797) | about 2 years ago | (#42351761)

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 flat on the top.

As to using tubes for your stereo, well, sure, if you're going to turn it up to 11...

I don't get it. (1)

Narcocide (102829) | about 2 years ago | (#42344095)

What is the practical application of being able to freely apply even more jack/plug torsion exactly?

Today's news at 5 (2, Funny)

skitchen8 (1832190) | about 2 years ago | (#42344119)

A local contractor severed a wire today, killing 5 from heavy metal poisoning.

Re:Today's news at 5 (3, Informative)

viperidaenz (2515578) | about 2 years ago | (#42344195)

Good thing Indium and Gallium aren't toxic or heavy metals then eh

Re: Today's news at 5 (3, Funny)

skitchen8 (1832190) | about 2 years ago | (#42344215)

Yeah, okay, someone mod me down :( I tried to be funny, can't fault a man for trying.

Re: Today's news at 5 (1)

geekoid (135745) | about 2 years ago | (#42347893)

yes, yes you can.

Pinching (0)

Anonymous Coward | about 2 years ago | (#42344125)

Sounds like you could simply pinch the wire to cut off any electric/data flow. That's a huge drawback.

A book falls on your wire? Desktop loses power.
Push your keyboard back a little and pin a wire against the wall? Desktop loses power.
Etc...

However, sounds like that could be a useful feature as well: Power cut off while too much pressure. I don't have a clue if this would work better than any of the existing pressure sensors. I don't know how those work.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42344385)

It's unlikely you could pinch it thin enough to do what you're describing. This is electron flow, not simple liquid pressure that you can cut off by pinching a hose.

Re:Pinching (1)

Fluffeh (1273756) | about 2 years ago | (#42344745)

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] .

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42344865)

No, it would not stop electron flow. It would reduce the cross sectional area, and could thus marginally increase the resistance in the wire, but it would not stop electrons like it would a flow of liquid. Electrons are *REALLY* tiny... far tinier than what it would take to simply make a seal tight against even single molecules of liquid.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42345395)

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.

Re:Pinching (1)

VortexCortex (1117377) | about 2 years ago | (#42347535)

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 fires start. The whole electrical code falls under the NFPA for this reason (National Fire Protection Agency).

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42351651)

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.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42348157)

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.... gold, which can be pressed to thicknesses on the order of only a handful of atoms across). And the scale of how tiny a gap we're talking about here is small enough that the electrostatic repulsion between electrons is going to be a dominant force, and is going to actively push things away, keeping an almost infinitesimally small gap open, and I'd dare say would require many tons per square inch of pressure to achieve.

Long before you get to this point, the reduced cross section of wire would increase the resistance in the wire enough to cause any ordinary insulation around the wire to start to melt. If the issue of preventing leakage of the fluid can be addressed (which, admittedly, it has not been so far), then that level of abuse (because in practice, it would probably take deliberate abuse to create the scenario where that much force is acting on it, and not something that happens coincidentally) would be about as serious as if the wire had simply been cut. And in general, that kind of pinching force acting on the wire would tend to break it anyways, unless it is made out of some extraordinary material.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42351547)

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 electron flow would just stop. Another point is that if the tube is crimped quickly it will act like a switch and there will not be enough time for heat to build up.

As for the scenario; did you look at the picture in a previous post? It does not take a lot of force. All it requires is a loop and pulling the ends a bit to create a pinch in the tube much like is done to crimp off a water hose. There is a point at which the sides are close enough to stop water flow. That same kind of crimp is enough to separate the liquid conductor. Remember that the tube elongates 8 time that means it is pretty elastic. That means that it would crush pretty easily. I bet I could crush the tubing with my fingers enough to separate the conducting fluid.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42352855)

...it just has to be small enough to separate the liquid conductor

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.

I bet I could crush the tubing with my fingers enough to separate the conducting fluid.

Enough to stop the liquid from flowing through the gap, yes... not enough to stop it from conducting electricity.... at least not without creating sufficient pinching force that you actually cut the wire.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42357197)

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 no electron flow. If the sides of the tube are touching each other what atoms are exchanging electrons so the charge moves? It isn't the tubing as that is an insulator. Electrons do not flow. They jump from one atom to another. If two atoms of the liquid metal are not touching there will be no electron flow. With enough energy electrons can cross short gaps. That is called a spark and takes a lot of voltage to accomplish. That is far beyond the voltages in a headphone wire.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42360105)

Where there is no liquid, as in a pinch, there is no electron flow

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 liquid that doesn't compress, and not merely partially filled, leaving much compressible gas inside, so pinching it doesn't leave the liquid with anywhere to really flow to. The container is flexible, but all it can do is stretch to accommodate the change in the cross sectional area of the wire. 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). In the end, any amount of nominal pressure pinching would not accomplish this. No matter what mechanism you used to pinch it, the effect would be exactly the same as if you took scissors to the wire, which also accomplishes its effect by simply pinching.

I can't really assert that you couldn't possibly pinch it this tightly at all, only that if you were to, the result would also be a severed wire, and that such high amounts of stress are not liable to happen in practice.

Bearing in mind also that nowhere in this article does it even imply that this kind of wire would be applicable to industrial situations where such forces would have a moderate chance of occurring. The power levels implied by the article are on the order of what you'd get in a set of headphone wires, and not what you'd be using to run power to appliances.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42362473)

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 that can elongate by 800%.

Industrial situations are not the problem. All it takes is a loop in the wire, a closed door or someone stepping on the tube. I think what may be causing the issue is that you are thinking of large tubes while I am thinking of tubes around 1/8" which would replace headphone wiring.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42362657)

It can elongate 8 times it's original length.

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.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42365361)

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 a much larger area. Shearing forces cut while crushing forces generally cause deformation but do not cut. I have some silicone tubing that is about 1/8" outside diameter. It is very stretchy and probably would accommodate the liquid conductor quite well. I can elongate it quite far and I can crush it closed with my fingers without cutting it..

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42365937)

But when it elongates, the cross sectional area also reduces... The inside volume remains constant. It doesn't magically create more volume for the liquid core to seep into and liquid dont compress very easily like gasses do. The net result is that there won't be any place for the liquid you are trying to displace by pinching it to go to

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42371329)

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.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42373441)

A balloon's elasticity is such that it's volume can be increased considerably past a point of normal inflation. As you stretch the balloon, the thickness of the skin changes, and it doesn't necessarily have to get skinnier in another dimension like this wire does. With this wire, as you stretch it, the cross sectional area decreases, so the internal volume stays constant. The volume of liquid that you would be trying to squeeze out of the space where you are pinching would have nowhere to go... and the section itself that you are reducing the cross section of won't expand to accommodate the liquid because you are pinching it and preventing that section from lengthening.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42373869)

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 to accommodate the liquid displaced by the pinch. I am not talking about pinching the whole tube flat as that is impossible. As I stated, if one pinched 5% of the length of the tube flat there is plenty of elasticity to accommodate the shift in fluid.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42375631)

The fact is that if the tube can lengthen means it can also bulge

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.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42376159)

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 the math I showed you in previous posts. To accommodate a 1/2" pinch in a 5' wire it would have to bulge by less than 2%. Not a big deal in a tube that can elongate 800%.

Have you ever played with elastic tubes? I doubt it. So how are you such an expert in their properties? I have in my possession some silicone tubing that would work quite well for this application. It has a thick wall to resist bulging due to the weight of the liquid, will elongate quite well and will also bulge without breaking if enough pressure is applied. Have you looked at a real piece of tubing or are you just guessing? The advancement is not the tubing it is the alloy in the conductor.

So far you have been incorrect in how electron charge flows (the electron themselves do not), You have no idea how elastics work (if the can elongate along a tube they can also elongate around the circumference causing bulges). You have no idea how to tune elastics (the tube can be stiff enough to support the weight of the liquid but still deform under enough pressure). You have shown that you can not differentiate shearing force and crushing force. You have no concept of how small a change in the tube would be required to accommodate a crimp. So far you have shown no understanding of electricity, mathematics, physics or materials science and no desire to learn therefore this will be my last post. I am tired of talking to a brick wall.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42384751)

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 experiencing only modest amounts of pressure from one side, such as what you get with a water hose, and not something that you're liable to experience in a non-industrial setting.

But to actually cut off electricity, assuming a conductive liquid core, you are going to have to squeeze it so tightly that not even a single molecule of thickness exists inside the body of the tube across the gap you are squeezing. This is quite a bit thinner than what you need to stop water pressure for a garden hose, and is a *LOT* harder than you might think... since even solid objects that appear to be touching on a macroscopic scale are not *REALLY* physically in contact with eachother at an atomic scale - rather, the electrostatic repulsion between their atoms' electrons will push to keep the substances separated by an distance which is *EASILY* wide enough for electrons which are being drawn by an opposite charge in a conductive material to pass But of course. in general, the level of force required to even get the material to this stage would probably cut the material.

But assuming that it could survive those forces, then the resistance of the wire would rise so sharply as that tiny a cross section was approached, that the heat would melt the insulation, and with a liquid core, it would render the wire just as useless as if it had been physically cut.

Finally, there's also the fact that at these kinds of scales, there's not a whole lot of difference between conductor and insulator, even the best insulators will not prevent electricity from flowing some small distance, and over the gap that you are trying to squeeze the liqud out of, even if you were to actually separate one side of the tube from the other, keeping the tube itself intact, across the gap itself between the two sides of the tube and where the tube is being squeezed, there would be many millions or even billions of isolated pools of the conductor that, themselves, would be close enough to eachother that electricity could effectively arc between them through the insulative material, while still being far enough apart that nominal amounts of macroscopic pressure, such as what you experience in a water hose, would not actually push through.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42385243)

Sorry but you are a moron.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42392629)

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 you're convinced that I'm a moron, then there's not much point in continuing this. But for the record, resorting to ad hominems doesn't exactly strengthen your position.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42393293)

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 gap no electrical charge will flow. The potential needed to jump a mm of air is about 3kV [wikipedia.org] . A 5V charge would not make it. It is even worse when there is not enough space for air to be so there is no possibility if ionization. You can not seem to get it through your head that electron flow is not separate from the atoms that they make up. Electrons are not tiny bits of matter that flow like water. They are charges that move from atom to atom in material that readily accepts and releases charges, conductors, and is stopped by materials that do not exchange charges well, insulators, What you continue to ignore is that if there is no conductor, at the voltages we are talking about, there is no charge flow.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42395617)

[the crimp] separates the conductor

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.

Re:Pinching (1)

jklovanc (1603149) | about 2 years ago | (#42397655)

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 to prove that there is no air in the tube so any results would be suspect at best. You still have not described how a n elastic material that can elongate 800% can't bulge by less than 2%.

you are going to have to squeeze it so tightly that not even a single molecule of thickness exists inside the body of the tube across the gap you are squeezing. This is quite a bit thinner than what you need to stop water pressure for a garden hose,

If the crimp is tight enough to stop molecules of water under pressure the why is it not tight enough to stop molecules of metal under very little pressure? Since it is stopping the liquid metal, the pinch would separate it.

There are two points you repeatedly get wrong;
1. Electrons do not flow outside of a conductor.
2. Elastic materials stretch in all directions.
Go to a high school or university and ask a physics instructor. They will explain it much better so that you can understand basic physics.

Re:Pinching (1)

mark-t (151149) | about 2 years ago | (#42398583)

If the crimp is tight enough to stop molecules of water under pressure the why is it not tight enough to stop molecules of metal under very little pressure

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.

Re:Pinching (1)

hankwang (413283) | about 2 years ago | (#42357315)

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... (1)

sycodon (149926) | about 2 years ago | (#42344127)

...are finally finding something besides how to hack into some software.

They killed the old gag. (0)

Anonymous Coward | about 2 years ago | (#42344227)

We used to send the rookies to the supplier or back to the plant office for "Cable Stretchers" because we'd cut the cable too short. Now they come up with stretchable wire. What do you bet the researchers where once those rookies.

So the old joke is true then... (0)

Anonymous Coward | about 2 years ago | (#42344249)

...you will actually be able to be low on network fluid?

Isn't this 30 year old technology? (4, Interesting)

Anonymous Coward | about 2 years ago | (#42344255)

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?

Re:Isn't this 30 year old technology? (0)

Anonymous Coward | about 2 years ago | (#42345205)

Same alloy, completely different sheath material allowing much higher elongation factor.

Headphones ... (0)

Anonymous Coward | about 2 years ago | (#42344273)

Can't wait to buy a headphones with this technology ...

Re:Headphones ... (1)

Osgeld (1900440) | about 2 years ago | (#42344787)

why, so you can fuck up your headphone jack even more?

Re:Headphones ... (1)

jklovanc (1603149) | about 2 years ago | (#42345385)

So you can say "Get off the cord ; I cant't hear the music"?

What??? (1)

cortcomp (2798707) | about 2 years ago | (#42344293)

Now when i bill a customer for "topping off their network fluid" it can actually be true?

gallium, while not very toxic, has other issues. (1)

queazocotal (915608) | about 2 years ago | (#42344305)

Re:gallium, while not very toxic, has other issues (1)

flimflammer (956759) | about 2 years ago | (#42344671)

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.

Re:gallium, while not very toxic, has other issues (0)

Anonymous Coward | about 2 years ago | (#42344823)

Those fancy wires are going to be expensive. Indium is around $240 a pound these days, versus $3.50 a pound for copper.

NCSU must be having a hard time (0)

Anonymous Coward | about 2 years ago | (#42344309)

If they think that what amounts to the same as filling a rubber hose with water and stretching it, is somehow newsworthy, they must be really suffering in their fundraising efforts. But I admire their chutzpah, because there's absolutely nothing of interest or merit if the metal is already liquid.

Stevens was right. (1)

samriel (1456543) | about 2 years ago | (#42344317)

So, a network made from this type of wire really would be a series of tubes?

Jasper (1)

Impy the Impiuos Imp (442658) | about 2 years ago | (#42344817)

Hey, I just made stretchable ice!

That's one way to do it. (2)

SuricouRaven (1897204) | about 2 years ago | (#42345459)

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.

Re:That's one way to do it. (1)

jklovanc (1603149) | about 2 years ago | (#42345749)

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.

Tired Musician (0)

Anonymous Coward | about 2 years ago | (#42346189)

Can't we just do away with the wires altogether please?

Do you suppose it could form other solid shapes? (1)

amanaplanacanalpanam (685672) | about 2 years ago | (#42346553)

Like, for example, knives...and stabbing weapons?

Speaker cables (1)

deek (22697) | about 2 years ago | (#42346987)

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. ;-)

Re:Speaker cables (1)

hankwang (413283) | about 2 years ago | (#42351215)

until it gets squeezed under a chair leg or from pulling it around a corner.

Internet Applications (1)

RivenAleem (1590553) | about 2 years ago | (#42349509)

Finally we can get rid of all that copper wiring and replace it with tubes of liquid metal, as it should have been!

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