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Liquid Metal Capsules Used To Make Self-Healing Electronics
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."
I don't know if I'd want to be on a crack team. I'm more of a coke team kind of guy.
Having to work for a living is the root of all evil.
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.
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 for an idea why.
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.
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.
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.
Authorities who disagree with you include:
The Encyclopedia Britannica
The Cambridge Advanced Learner's Dictionary & Thesaurus
The US National Institute of Standards and Technology
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.
traces don't break. they suffer from electromigration. 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.