Boffins build elastic wires with liquid metal Researchers at North Carolina State University have shown “conductive wires that can be stretched up to eight times their original length while still functioning.” The wires have been tested, and demonstrated in the video below, to work perfectly well as headphone wires. Sound continues to reach the headphones even as the …
Plastic Deformation is usually (well in my nick of the woods) meant to denote deformation that doesn't return to the original state, whereas elastic deformation does. So you're right that they use the word strangely here, although it's not exactly the antonym of elastic (it's still deformable, after all).
I do think so. Network cable is capable of dealing with lengths from 1m to 100m... so unless the 100m patch cable uses thicker wire, it will have a resistance 100 times that of the 1m cable. Same for headphone cables, which come in widely different lengths, yet seem to work just fine. Perhaps because the resistance of the wire itself is negligible compared to the resistance of other components in series to it?
It’s not so much resistance as impedance; the cables are designed to have a certain characteristic impedance per unit length (capacitive and inductive effects are present too). If there was a stretchy part in, say, a twisted-pair Ethernet cable, then the twisting rate would vary, as would the conductor spacing (as the insulation stretches it must get thinner to compensate). This would result in a less-than-ideal section for noise resistance… but probably no worse than bunging in a 6-inch shielded patch cable to make up a slight length difference.
1. if you are serious about your network you are never 2 inches short. Ideally you should know how to terminate your cables by yourself and you will always have just the right length, otherwise you just have to buy a slightly longer cable.
2. I agree that the variation in impedance is not going to make a huge difference in the end; but depending on the physical properties of the cable, the constant tension may have desastrous effects. Just watch the cables jump out of the sockets one by one as the plastic jacks weaken over time... physical tension on my Ethernet cables? Not on my watch!
Strikes me that the volume of the conductor in the cable must remain constant, so if it gets longer, it gets proportionally narrower. Which means, as the researchers point out, that the resistance rises.
While the resistance isn't specified, it does imply two effects: first the decrease in signal level into any low or medium impedance load (e,g, headphones, and it really isn't going to work for cat-5...) and secondly the power dissipation in the cable itself,and therefore self heating. How friendly is boiling Indium/Gallium vapour to those inadvertently breathing it?
@Patrick R - 'increase' means it has, like every other non-superconductor, resistance. Irrespective of what that is, there will be a voltage across that resistance if current is flowing through it (i.e. it's not driving an infinite input impedance). If the cross sectional area is reduced - which it must be if the volume remains constant and the length increases - then the resistance, which is proportional to area and inversely proportional to length, will increase.
When the resistance increases, the power dissipated in the cable (remember P=IV?) will increase also. You might like to consider the case of a fuse blowing: it dies because it can no longer dissipate the power it is required to and it melts - this cable, which is already fluid, will simply heat until it boils. At which point you have a flexible plastic container around hot metal vapour.
This is electronics 101. While I may have exaggerated for effect, you can guarantee that the amount of metal used will be no more than the makers can get away with, which will render it more, not less, likely to accidental overload.
The headphones flying off your head, slamming into your hi-fi, overturning your coffee mug and scattering a pile of CDs, papers and stuff all over the room in the process...
That of course presumes that someone would actually use the stretching effect while ignoring the highly uncomfortable feeling of the phones being constantly tugged by the elastic wire, which brings me back to the question - what is the frikkin' point?
Also nice to know that if your insulation breaks your wires will leak out, happily seeking out and shorting any bit of electrical equipment that they can find.
Ignoring the statement in the article about possible applications in wearable computing, I could imagine this as a very useful temporary wire. Imagine your setting up a concert, a jack cable snaps and the replacement(which you should have anyway) is missing, whip out your elastic wire which is nice and stretchy, allowing it to fit many uses.
I bust two sets of bluetooth earbuds by killing the cables, but they do get used daily. Shure have solved this problem anyway - you can replace the cables and plug new ones into the earbuds. Maybe other companies have similar solutions too. I'm sure the stretch-armstrongness has other useful applications though.
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As I recall gallium makes mercury look woosy when it comes to amalgamating with aluminium to ruin any strength it had. Small scratch and the gallium creeps in, and carries on into the aluminium block which will still look quite unchanged on the surface, yet be quite brittle and crushable under finger pressure!
Indeed.
And there are very special rules indeed about how to package gallium for transport by plane. The old Russian method used to be a couple of ziploc style plastic bags. Which is fine in cold weather. But mid summer in hot places, well Ga melts at 27 oC. And liquid Ga spilling onto the Al alloy floor of a cargo hold. In theory it should just eat right through.
There is a story that this happened once: no idea whether it's actually true though.
Its useless for headphones if theyll ever be worn near, say, a zip? Or while in an aircraft- take a look at youtube to see what Gallium does to aluminium. Network cable would find itself rendered useless if stretched, too (differing resistive/capacitive properties would really screw with the signal properties). And you couldnt keep a bundle laying around the house because if they got hot you'd end up with heavy metal poisoning.
I really hope this doesnt catch on...
Havn't telephone handsets been using coiled wire for decades to solve the same problem? Liquid metal wires might have a niche when you need to send high-current over a variable-length pathway within space contraints which prohibit the use of coiled or folded wire, but that is a very small niche. Could make a nifty distance-measuring device in robotics though.
Many years ago I helped develop a coiled audio cable. The problem with it is that it is fine when the things on each end are heavy, but not when they are light. Like ear buds...there must be enough return force to hold the thing together in the return position. What is needed is a constant force spring, but Dr Hooke and Prof Young say it wont work.
AFAIK, all the major manufacturers stopped making retractable headphones for your phone (The ones that wind up into a little cassette) mainly because the wires and connections inside kept snapping during the strain of winding and unwinding.
If they could use this tech to solve that issue then I would be a very happy bunny as I loved that form-factor.
This little tip is useful, I made up some DIY removal alloy with bismuth and indium, however BiSn works fine when mixed with both tin/lead and slightly less well with tin/copper.
Best to add a little (30%) indium for that.
Ch*quik is essentially the same but has some other metals including possibly gallium to make it flow better.
Liquid metal roll up piano/PC keyboards, now we are talking.
Lets see someone break THAT! :-)
If you can stretch this cable 8 * its length without degradation then why not pre-stretch it in the factory and make 8 * as much money (duh!)
I'm sure these guys (and gals) have come up with something that is groundbreaking in its own way (and all credit to them), one-way stretchy cable isn't it.
I believe many telephone handset leads still use a special type of wire called "tinsel" where there is a nylon fibre core wrapped in one or more helical windings of copper foil. As you stretch the wire the helix extends to give you a much longer strain before failure- massively reducing cable failures on kinks, bends and stretches.
It seems to have gone out of fashion I suspect because:
It has a higher resistance so isn't ideal for low impedance headphones
It's a complete pain in manufacturing- special insulation displacement connectors are required and it's kind of tricky to solder!
Wonder if this would work if LEDs were placed inside the cores, with axial connectors?
They might be prone to shorting out but this is a non issue as the sheer number of them makes a flexible, stretchable light source that would blow OLED out of the water.
Just have bits of copper like they use with EL wire and sheet, so the segments can be cut up and soldered together.
Ideal for clothing, safety applications etcetera.
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