Self-healing electronics could work longer and reduce waste

December 20, 2011
This shows self-healing electronics. Microcapsules full of liquid metal sit atop a gold circuit. (Top) When the circuit is broken, the microcapsules rupture (center), filling in the crack and restoring the circuit (bottom). Credit: Scott R. White

When one tiny circuit within an integrated chip cracks or fails, the whole chip – or even the whole device – is a loss. But what if it could fix itself, and fix itself so fast that the user never knew there was a problem?

A team of University of Illinois engineers has developed a self-healing system that restores electrical conductivity to a cracked circuit in less time than it takes to blink. Led by aerospace engineering professor Scott White and materials science and engineering professor Nancy Sottos, the researchers published their results in the journal .

"It simplifies the system," said chemistry professor Jeffrey Moore, a co-author of the paper. "Rather than having to build in redundancies or to build in a sensory diagnostics system, this material is designed to take care of the problem itself."

As electronic devices are evolving to perform more sophisticated tasks, manufacturers are packing as much density onto a chip as possible. However, such density compounds reliability problems, such as failure stemming from fluctuating temperature cycles as the device operates or fatigue. A failure at any point in the circuit can shut down the whole device.

"In general there's not much avenue for manual repair," Sottos said. "Sometimes you just can't get to the inside. In a multilayer integrated circuit, there's no opening it up. Normally you just replace the whole chip. It's true for a battery too. You can't pull a battery apart and try to find the source of the failure."

Most consumer devices are meant to be replaced with some frequency, adding to electronic waste issues, but in many important applications – such as instruments or vehicles for space or military functions – electrical failures cannot be replaced or repaired.

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Professor Scott White and his team of scientists have developed a new way for electronics and batteries to repair themselves. Credit: Katherine Gatsche, University of Illinois

The Illinois team previously developed a system for self-healing polymer materials and decided to adapt their technique for conductive systems. They dispersed tiny microcapsules, as small as 10 microns in diameter, on top of a gold line functioning as a circuit. As a crack propagates, the microcapsules break open and release the contained inside. The liquid metal fills in the gap in the circuit, restoring electrical flow.

"What's really cool about this paper is it's the first example of taking the microcapsule-based healing approach and applying it to a new function," White said. "Everything prior to this has been on structural repair. This is on conductivity restoration. It shows the concept translates to other things as well."

A failure interrupts current for mere microseconds as the liquid metal immediately fills the crack. The researchers demonstrated that 90 percent of their samples healed to 99 percent of original conductivity, even with a small amount of microcapsules.

The self-healing system also has the advantages of being localized and autonomous. Only the microcapsules that a crack intercepts are opened, so repair only takes place at the point of damage. Furthermore, it requires no human intervention or diagnostics, a boon for applications where accessing a break for repair is impossible, such as a battery, or finding the source of a failure is difficult, such as an air- or spacecraft.

"In an aircraft, especially a defense-based aircraft, there are miles and miles of conductive wire," Sottos said. "You don't often know where the break occurs. The autonomous part is nice – it knows where it broke, even if we don't."

Next, the researchers plan to further refine their system and explore other possibilities for using microcapsules to control conductivity. They are particularly interested in applying the microcapsule-based self-healing system to batteries, improving their safety and longevity.

Explore further: New recipe for self-healing plastic includes dash of food additive

More information: The paper, "Autonomic Restoration of Electrical Conductivity," is available online at … /adma.201102888/full

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1 / 5 (2) Dec 20, 2011
Ok : First : Indium world resources are almost depleted...
second : yes... of course, makers of electronic devices ARE willing to fabricate products that will last forever so that we really don't need to buy a new one when it stops working for no apparent reason after a couple of years...

not rated yet Dec 20, 2011
It would probably be good for repairing damage from static electricity discharges, I read they are a reason why most electronics end up failing .
1 / 5 (3) Dec 20, 2011
The self-healing circuitry of the latex and blood-vesseled humanoids will allow them, after being unleashed among us, to survive our attempts to terminate them with extreme prejudice...
not rated yet Dec 20, 2011
I think this will first taken into use at military and satellite tech. Those are places where repair costs are enormous compared to added cost of manufacture of these parts.
1 / 5 (3) Dec 20, 2011
So what if you have a circuit that can heal itself and last nearly forever; when it will become obsolete in a year, and you have to update again. I have many old computer hulks that have perfectly good, working parts. Unfortunately, none of them will run today's software. What a farce, unless you use the self healers for space travel, where you can't simply go to the store to repair or buy new... of little or no use here on Earth; where companies would fast go out of business if they didn't build in a limited lifetime to their products.
5 / 5 (1) Dec 21, 2011
There are many uses for this. Don't just focus on consumer electronics.

Think about embedded stress sensors in bridges/buildings/roads, embedded medical devices (pacemakers, insulin pumps, defibrillators, etc. ), sattelites, amplifiers in deep sea cables, ...

Basically anything that is hard and/or costly to get to and replace.

Yes: consumer electronics are obsolete after a few years, but sensors and embedded hardware in industrial machines are not. They don't need to be upgraded and replaced once they are in place. The longer they last the better.

It's very costly to have your factory grind to a standstill because one part along the production chain fails - so this type of treatment could quickly pay for itself.
not rated yet Dec 21, 2011
I can see it has some uses in High Reliability systems, but cannot see this ever being used in consumer electronics.
Production cost is critical and products have a short lifecycle due to obsolescence, it's easier and cheaper just to upgrade. It also doesn't address many of the failure modes of semiconductors and would be very unlikely to help repairin ESD damage. And with Geometry of 10 microns it's simply orders of magnitude too large for use in chips.

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