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Hardware Science

Liquid Metal Capsules Used To Make Self-Healing Electronics 135

Posted by samzenpus from the terminator-edition dept.
MrSeb writes "A crack team of engineers at the University of Illinois has developed an electronic circuit that autonomously self-heals when its metal wires are broken. This self-healing system restores conductivity within 'mere microseconds,' which is apparently fast enough that operation can continue without interruption. The self-healing mechanism is delightfully simple: The engineers place a bunch of 10-micron (0.01mm) microcapsules along the length of a circuit. The microcapsules are full of liquid metal, a gallium-indium alloy, and if the circuit underneath cracks, so do the microcapsules (90% of the time, anyway — the tech isn't perfect yet!). The liquid metal oozes into the circuit board, restoring up to 99% conductivity, and everything continues as normal. This even works with multi-layer printed circuit boards (PCBs), such the motherboard in your computer, too. There's no word on whether this same technology could one day be used by Terminators to self-heal shotgun blasts to the face, but it certainly sounds quite similar. The immediate use-cases are in extreme environments (aerospace), and batteries (which can't be taken apart to fix), but long term we might one day buy motherboards with these self-healing microcapsules built in."
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Liquid Metal Capsules Used To Make Self-Healing Electronics More

Liquid Metal Capsules Used To Make Self-Healing Electronics

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  • Crack Team? (Score:5, Funny)

    by sgt scrub ( 869860 ) <saintium@nOSPaM.yahoo.com> on Wednesday December 21, 2011 @02:29PM (#38451862)

    I don't know if I'd want to be on a crack team. I'm more of a coke team kind of guy.

    • This kind of story makes me sad. So much wasted potential - Think of how much more this team could have achieved if they had only stayed off drugs.

  • In 1972... (Score:5, Funny)

    by Anonymous Coward on Wednesday December 21, 2011 @02:29PM (#38451864)

    A crack engineering unit was sent to prison by a military court for a crime they didn't commit. These men promptly escaped from a maximum security stockade to the Los Angeles underground. Today, still wanted by the government, they survive as soldiers of fortune. If your circuits have a problem, if no one else can help, and if you can find them, maybe you can hire... The A-Team.

  • Does not sound cheap.

    • Re: (Score:2)

      by durrr ( 1316311 )
      Used in very tiny proportions.
      Although possibly enough to expand a short circuit, turning that supposed battery saving miracle into a cascading disaster, blowing your leg off instead of just setting your pocket on fire.

      • Re: (Score:2, Offtopic)

        by ackthpt ( 218170 )

        Used in very tiny proportions.

        Although possibly enough to expand a short circuit, turning that supposed battery saving miracle into a cascading disaster, blowing your leg off instead of just setting your pocket on fire.

        This is the way the world ends. Not with a bang or a whimper, but a BZZOWNNT!!!

      • I think they'd probably design the circuits so that there wasn't enough of the liquid metal to reach the next wire over. That being said, this probably only works under normal gravity, so what you're suggesting might be something of an issue in space.

        • Re: (Score:2)

          by durrr ( 1316311 )
          The wires probably break under shock most commonly, as such they'd be rather dense to not test various abnormal G scenarios, most likely transient high-G scenarios, in microgravity the surface tension is likely to keep things in order.

          • Re:a gallium-indium alloy (Score:5, Insightful)

            by Moryath ( 553296 ) on Wednesday December 21, 2011 @03:09PM (#38452352)

            And that's why this is probably useless for consumer grade electronics.

            I mean really - how often do you break TRACES in a motherboard or PCB in any home consumer product? I haven't ever seen a failure like that get out of QC. The things that kill consumer electronics are corrosion, solder point failure (usually from overpressured heatsinks or heat based warping, see RROD), bad/exploding capacitors, and the occasional power surge or ESD damage.

            MAYBE in aeronautics? Maybe maybe MAYBE in automobiles, if you have a PCB somewhere controlling a multifuel system. But for consumer grade home electronics? Not remotely necessary.

            • Re: (Score:3)

              by EdIII ( 1114411 )

              Considering the incredible marketing effort and designed failure in consumer electronics to always buy new crap, I really have to wonder if the average consumer electronic would survive long enough to need this technology.

              I have a Number Nine 128 video card still working on an old P4 server. That's damn near 20 years old I think. No cracks in the PCB on that.

              If I have motherboards that are 3,5,10 years old still working just fine and I fail to see the point of this technology in consumer products. Milita

            • I recall a similar idea about a "self-healing" plastic that had microspheres with chemicals that would form some new plastic when they broke. These material advances are cool in that they make materials that are more durable and can last longer before ultimate failure. In normal consumer electronic usage, this material is not very useful like you say. Consumer electronic internals aren't subjected to a lot of physical stress like bending or shear forces and therefore are not a major fail point. In the t

            • Re:a gallium-indium alloy (Score:5, Interesting)

              by jank1887 ( 815982 ) on Wednesday December 21, 2011 @03:43PM (#38452792)

              traces don't break. they suffer from electromigration [wikipedia.org]. I.e., where the constant collision of electrons with the metal lattice eventually creates voids in the metal. Becomes more of a problem with higher power processors and narrower conductors. some metals are more susceptible as well. (aluminum more than copper, i think).

              And similarly, they would get hot (due to the high current density in the near break) before they break, and this heat could trigger the liquid metal release. There are applications for high-reliability electronics. I think the automotive sector is the one that most easily comes to mind for the consumer market. Long use equiment, like medical equipment maybe too.

              Also, don't forget, the equipment you have is designed to operate as long as necessary without the types of failures this would solve. Given this tool, could they be designed differently? More efficiently? Smaller? Maybe.

              • Re: (Score:2)

                by Kneo24 ( 688412 )
                Oh, traces break. I've seen it numerous times - granted it's due to other sources causing them to break. Besides, if enough electromigration happens, you can effectively call it, "broken", as in it doesn't work properly anymore. Seriously, playing the game of semantics here is pointless, though it was a good effort on increasing the vocabulary of the community.

            • Re:a gallium-indium alloy (Score:4)

              by triffid_98 ( 899609 ) on Wednesday December 21, 2011 @05:51PM (#38454338)

              I mean really - how often do you break TRACES in a motherboard or PCB in any home consumer product? I haven't ever seen a failure like that get out of QC. The things that kill consumer electronics are corrosion, solder point failure (usually from overpressured heatsinks or heat based warping, see RROD), bad/exploding capacitors, and the occasional power surge or ESD damage.

              Agreed 100%. Its highly unusual for a PCB to fail, 90% of the time it's been bad solder joints or bad caps which can then escalate into other problems. Solder joints go bad due to heat or vibration or just being poorly soldered in the first place.

              This problem is going to get much worse before it gets any better. lead based solders help prevent joint cracking and they're now illegal in the EU. As a result all new electronics use lead-free formulations. This means more heat/vibration related failures than ever, all because more politicians demanded we 'think of the children!'(tm)

            • Re: (Score:3)

              by ogdenk ( 712300 )

              And that's why this is probably useless for consumer grade electronics.

              I mean really - how often do you break TRACES in a motherboard or PCB in any home consumer product? I haven't ever seen a failure like that get out of QC. The things that kill consumer electronics are corrosion, solder point failure (usually from overpressured heatsinks or heat based warping, see RROD), bad/exploding capacitors, and the occasional power surge or ESD damage.

              MAYBE in aeronautics? Maybe maybe MAYBE in automobiles, if you have a PCB somewhere controlling a multifuel system. But for consumer grade home electronics? Not remotely necessary.

              I don't know.....if they could find a way to apply this to BGA chips......

              Seriously.... the modern BGA package was the stupidest cost cutting measure in history that has caused the average laptop to last maybe 20% as long as laptops made 10 years ago. I doubt Taiwanese 6-yr-olds in the sweatshop X-Ray every board and make sure the solder balls are perfectly uniform.

              I want a REAL computer again instead of a disposable consumer entertainment devices. But since the consumer market is so large, pro users and

        • Re: (Score:2)

          by fnj ( 64210 )

          Why would you suppose it only works under normal gravity? The wetting phenomenon does not depend on gravity at all.

    • I once worked for a company that tried to get something like this to work. Wetting was a major problem. PCB traces are prone to oxidation anyway, and if they are in buried layers then they are prone to surface contamination from the epoxy. Although in theory cracks should be clean surfaces, the GaIn has to get there in the first place, and in doing so its own surface may be contaminated. Even a very thin layer of oxide or an organic monolayer may well be enough to prevent wetting. I suspect that this will

    • Neither of those metals are cheap, even in minuscule proportions. Indium is about 80 times the price of copper at current rates, and gallium is not much cheaper.

      I suppose in some mission critical applications this would work, but I don't see this coming to consumer electronics, I'll bet it would just be cheaper to replace most devices than it would be to add this technology.

      • When you have something like a telecommunications satellite that costs $250 million and has to last 15+ years without maintenance, you aren't looking at the cost of materials for making micro capsules.

        You are paying upwards of $100 million / ton for the whole thing anyhow.

        • Re: (Score:2)

          by Kneo24 ( 688412 )
          I'm curious, what part of their last sentence did you not understand? They already conceded on the point that in some critical applications that this would work, but not in consumer grade electronics. I think anything costing as much as you stated would fall under the "mission critical application" idea.

  • Great, so we just need metric tons of gallium and indium, facilities to make it into a special alloy, then redesign all the circuit boards out there to be self-healing. Brilliant!

    • Only one Slashdot do you need to be told that "metric tons" don't exist - they are tonnes, and require no prefix.

      I have some indium, a sample rescued from a waste bin. I would really like a tonne of indium. You could buy an apartment with it.

      • Re: (Score:1)

        by Lashat ( 1041424 )

        Does that apply to the often used "metric shit-ton"? So, the correct usage would actually be shit-tonne?

      • Re:But Doc, we just need a little plutonium! (Score:5, Informative)

        by DRJlaw ( 946416 ) on Wednesday December 21, 2011 @03:34PM (#38452674)

        Only one Slashdot do you need to be told that "metric tons" don't exist - they are tonnes, and require no prefix.

        Authorities who disagree with you include:
        The Encyclopedia Britannica [britannica.com]
        The Cambridge Advanced Learner's Dictionary & Thesaurus [cambridge.org]
        The US National Institute of Standards and Technology [nist.gov]
        and about 16.5 million other hits on Google.

        For some reason, having the homonyms ton/tonne variously refer to a short ton (907.18474 kg), a tonne (1000 kg), or long ton (1,016.0469088 kg a.k.a. English ton) vexes some people. They prefer to specify a "metric ton" rather than so overemphasize "tonne" that they sound as if they have a speech impediment.

        The unit of measure exists by virtue of its pervasive use. The fact that you prefer an alternate equivalent does nothing to change that fact.

        • The gp has a sig which reads "Only on Slashdot does an AC get modded Informative for pointing out that the LHC is in Europe."

          The SI unit that equals 1000kg is a tonne. But the United States, in a fit of parochialism, has decided to rename it a "metric ton". To quote:

          Thus the spellings “meter,” “liter,” and “deka” are used rather than “metre,” “litre,” and “deca” as in the original BIPM English text; (ii) the name of the unit with symbo

          • Re:Let me explain (Score:4, Informative)

            by DRJlaw ( 946416 ) on Wednesday December 21, 2011 @05:06PM (#38453842)

            The SI unit that equals 1000kg is a tonne. But the United States, in a fit of parochialism, has decided to rename it a "metric ton".

            The SI unit that equals 1000 Kg is a megagram (Mg, or 10^6 grams). The tonne is not an SI unit [bipm.org], but, in a fit of nostalgia [oxfordwine.co.uk], has been metricized and accepted for use with the SI system.

    • How about they just start with bad solder joints that can fix the craptastic job done by the original manufacturers.

  • Not such a good idea (Score:5, Interesting)

    by ka9dgx ( 72702 ) on Wednesday December 21, 2011 @02:40PM (#38452018) Homepage Journal

    I know it would be an alloy... but Gallium isn't such a great thing to be shipping around in airplanes, etc..watch this youtube video of gallium eating an aluminum can [youtube.com] for an idea why.

    • that's because it wants to be an alloy. it will alloy with steel too. but once it is a stable alloy, it can be just fine. E.g.: Gallinstan [wikipedia.org] (68.5% Ga, 21.5% In and 10% Sn) being used as a replacement for mercury in a lot of liquid metal systems.

    • Re: (Score:2)

      by Menkhaf ( 627996 )
      MOD PARENT UP!!!!1111 Look at what common table salt does to water! http://www.youtube.com/watch?v=JD85OUkEKKw [youtube.com] (oh wait, NaCl != Na -- just like gallium != a gallium alloy)

  • The liquid metal oozes

    Sounds a lot like gravity is the main mechanism for deploying the liquid, in which case any circuit that is not facing "Up" cannot utilize this technology otherwise the liquid will just pour whichever direction is down, which is not always toward the circuit... Or am I just understanding this concept incorrectly?

    • Re:Delivery mechanism is what? (Score:4, Informative)

      by Anonymous Coward on Wednesday December 21, 2011 @03:08PM (#38452338)

      At those scales, the effect of gravity relative to static forces is very small. Very small amounts of liquid metal would spread in any orientation. For those who've soldered, you'll know that solder spreads through wires regardless of which way they're oriented. It takes to the surfaces. Only when you add too much does gravity begin to play a substantial role.

      I agree with another poster that whetting is going to be the hardest problem. Although knowing gallium, it's possible that their technique will allow it to alloy with the existing metal and for an amalgam, in essence actually permanently repairing the trace. One would have to experiment to know for sure, but it seems likely that this is the mechanism that is used.

      • I double checked the size of the capsules after I posted and thought about static as a possibility, but I did not want to accidentally sound like a moron, I would rather sound like an uninformed nerd that wants to learn.
        Thanks for the response confirming my thoughts!

      • Re: (Score:2)

        by Kneo24 ( 688412 )
        Someone mod this AC up as informative. They're spot on.

  • Ah yes, yet another ingenious solution to the wrong problem.

    The main problem these days with PC boards is the exact opposite-- tin whiskers growing BETWEEN the traces, not with traces breaking down.

  • And the formulary used will cause our capacitors to expand and leak self-healing fluid all over the motherboard.

  • It's not _that_ self healing. (Score:3)

    by Minwee ( 522556 ) <dcr@neverwhen.org> on Wednesday December 21, 2011 @02:48PM (#38452112) Homepage

    What happens when it breaks a second time? Then it's just as broken.

    This kind of thing may help resist a sudden, one-time shock, but it won't do a thing to protect electronics from ongoing wear. Perhaps if there were a way of notifying the device that it had been broken so that it could quickly inform the user and void its own warranty then it would be more useful.

    • If it breaks a second time it likely won't be in the same spot. And if it was, at least you got the extra runtime.

      As for the warranty... What's the point of a warranty that's void if the device breaks?

      • Re: (Score:2)

        by Minwee ( 522556 )

        If circuits broke entirely at random without any reason at all then that would be a fair assessment. It's more likely that breaks will be a result of circuit boards being placed under stress as a result of design flaws, and that will happen in the same place every time. I know a number of notebook computer owners who would be happy to demonstrate this.

        What's the point of a warranty that's void if the device breaks?

        You're thinking like a consumer again. The point is that it gives the manufacturer another excuse not to honour an otherwise expensive warranty, much like

        • Water damage detectors at least have a hint of it being the consumer's fault (even if they get tripped by other things in practice).

          "Warranty void if product breaks" is easily understood by the customer as "no warranty". So why not just have no warranty?

    • Re: (Score:2)

      by Hentes ( 2461350 )

      There are millions of places where a circuit board can break, so it's unlikely that it will break twice in the same spot.

  • How do they prevent this from creating short circuits under stress?

    • Re: (Score:2)

      by Kneo24 ( 688412 )
      In general PCB's are designed in a way where there's a layer of substrate (i.e. whatever the PCB is made out of) between that trace and the next one. I work with industrial electronics for a living. The biggest annoyance I see is when boards are literally fried from components blowing up. This can very easily cause the traces to go open. This alloy would attempt to keep the connectivity there which could cause further mishaps. The issue is compounded when the board is burned and the carbon in the board star
  • Subject says it all. nuff said.

  • Useless in the real world (Score:1)

    by Anonymous Coward

    While this has a certain cool factor it is pretty impractical. The chances of a copper trace failing due to shock or vibration are much smaller then the chances of the components that are soldered down failing. Copper is quite malleable. By the time you have deformed a PCB enough to destroy a trace you have probably cracked every surface mount part on the board.

  • printers (Score:1)

    by Anonymous Coward

    I guess we'll be stuck with "PC Load Letter" forever now

  • Doesn't add up (Score:5, Interesting)

    by Asic Eng ( 193332 ) on Wednesday December 21, 2011 @03:31PM (#38452624)

    The article states this technology is intended to automatically repair integrated circuits via "microcapsules, as small as 10 microns in diameter". Being charitable and going with 90 nm geometries (which we still used in our company last year - we are a bit slow) that's too large by a factor of 100. Interesting for PCBs, but not for integrated circuits.

    The article also states that the technology would fix things "so fast that the user never knew there was a problem" and then explains that "a failure interrupts current for mere microseconds".

    The summary corrupts that somewhat into the claim that "operation can continue without interruption". It's far too slow for that. Let's assume a rather slow 33 MHz bus - that gives us a clock period of 30 ns - so we'd miss at least 33 clock cycles in this scenario. This interruption might not be noticed by the user, if an error correcting protocol is used on the bus and the system retransmits. Otherwise you would get wrong data, and you have to assume that will be noticed sooner or later.

    Interesting technology on PCBs or communication wires, I could see it being used in safety-critical applications. On integrated circuits it doesn't seem feasible. Basically you make the transistors and wires on ICs already as small as you can. To repair the wires on the IC you now need to insert capsules into the wires to do the automatic repair - so they would be way smaller than the wires. If you could manufacture these structures you'd make the wires smaller though and then you'd lose your ability to insert the microcapsules ... there is no way to win that race.

    • On integrated circuits it doesn't seem feasible. Basically you make the transistors and wires on ICs already as small as you can. To repair the wires on the IC you now need to insert capsules into the wires to do the automatic repair - so they would be way smaller than the wires. If you could manufacture these structures you'd make the wires smaller though and then you'd lose your ability to insert the microcapsules ... there is no way to win that race.

      Along the same lines, if you need twice the room to have the capsule next to the trace/wire, you might as well just make the wire twice as thick and figure that this makes it tougher. To determine if this technology is worthwhile, they would have to compare time to failure between their system and one with traces that occupied the same volume as their wire+capsule combination.

      • Or alternatively, rather than making the wires twice as thick, you could implement the system twice and add some checker logic to find out if something has gone wrong. That's being used a lot on ICs for automotive applications, currently. (At least duplicated embedded CPUs and core logic - peripheral logic is checked with other means.)

        Also for safety applications you have to consider other fault sources like radiation flipping bits which occurs a lot more often than IC wires breaking due to aging. These ca

  • Finally has the technology to build the terminator from Terminator III (the "evil" one) .

  • Anything that adds cost to PCBs is bit of a no-no - I can't see how the "self-healing" benefit can factor into any PCB design (especially motherboards, which have the least layers possible to reduce cost) unless it is for some specialist application, where using such tech would warrant the extra cost involved.

    Cool, but, lets face it - not going to be every day.

  • Basically, this is a technology where, if a short develops and a circuit is broken, it will immediately repair the circuit?

    Are we sure that is a good thing?  If there is a power problem, for example, couldn't that just cause a new short to happen somewhere more expensive to repair?

    • You put in fuses or fuse-diodes for that reason. A random crack in a circuit line is not a good safety measure against shorts.
      Btw, this does not repair short circuits. It maintains connectivity. In a short circuit, there is too much connectivity, not too few.

    • Are we sure that is a good thing? If there is a power problem, for example, couldn't that just cause a new short to happen somewhere more expensive to repair?

      That's nothing. Imagine when there is a power "problem" because humans tried to switch off the Terminator, and it just causes a new circuit to override the power "problem".

  • It might be useful but in my 30 years of dealing with electronic equipment; I have encountered way, way more faulty components than a burnt or "faulty" run. Of the times I have found a toasted run, there was always a toasted component to go along with it.
  • My computer is so overclocked, I have a pipeline feeding this stuff in to keep repairing the motherboard!
  • Add liquid metal to a crack - what could possibly go wrong?
    If you can't answer that and call yourself an engineer then you don't deserve the title.

  • Isn't it better to focus on margins and making sure the worst case scenario is not capable of degrading circuits? If margins are a problem or electron migration is a potential issue be more careful and size your components accordingly.

    Even if the capsuls do their job they change the capacitance of the circut upon release right? 10-microns is hundreds of times the feature size of a modern process. So you don't know exactly what percent of the circut is restored you don't really have the capability to model

  • If they ever perfect this technology, it still won't make it into consumer products.

    2 reasons:

    First being that it would increase the cost of the product, which cuts into profit.

    Second, they want you stuff to break and be unfixable, so you HAVE to buy a new one.

    Best use of this idea: Headphones.

  • just a heavier crash, and the main board of the drone has problems. No idea what exactly breaks.

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