Could the electronics in planes 'self-heal' to keep them in the air?

Plane-ly sensible: There are hundreds of circuits in
aircraft, so a self-healing system could come in handy

• Researchers develop microcapsules that spill conductive liquid into circuit cracks

If a computer chip in an aircraft cracks or fails, it could be fatal, but researchers think they've found a solution - the self-healing chip.

It sounds like science fiction but 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.

When a crack appears, a microcapsule breaks open and releases liquid metal to get electricity flowing again.

Chip off the old block: The clever system can heal itself in mere seconds

 

 As electronic devices are evolving to perform more sophisticated tasks, manufacturers are packing as much density onto a chip as possible. 

However, such density increases 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,’ study author professor Nancy 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.

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 appears, the microcapsules break open and release the liquid metal contained inside.

The liquid metal fills in the gap in the circuit, restoring electrical flow.

Professor Scott White, another researcher on the project, said:  ‘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.

‘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 per cent of their samples healed to 99 per cent of original conductivity, even with a small amount of microcapsules.

The self-healing system also has the advantages of being localised 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.

The researchers published their results in the journal Advanced Materials.

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