IISc, Cambridge researchers develop ‘self-healing’ circuit

5 months ago 40
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BENGALURU: Researchers from the

Indian Institute of Science

(IISc) and University of


have developed what they call self-healing


that can help enhance durability of gadgets ranging from

wearable medical devices

to mobile screens.
Flexible electronic


such as foldable display screens, wearable sensors, and self-powered, portable energy devices are made up of millions of circuits composed of thin-film transistors (TFTs), IISc said. It added that these devices are prone to open-circuit failures due to mechanical stress from bending or stretching, electric stress arising from human contact, and corrosion from moisture or sweat.
Researchers from the two institutions — from the department of instrumentation and applied physics, IISc, and the department of engineering, University of Cambridge — started out with their research trying to answer whether the durability of such devices be enhanced by employing self-healing TFT circuits.
And, in a recent study, the team — Sanjiv Sambandan, Li Ding, Pushkaraj Joshi, James Macdonald and Virendra Parab — has developed such circuits and found them to be effective. The authors also describe a strategy for efficiently packaging these particles in the circuits for large-scale manufacturing. This could potentially widen the scope of applications of flexible electronic devices.
In laypersons' terms, Sambandan told TOI the concept was a lot like how entities in the blood rush to a site of injury to achieve clotting and healing. TFTs, he said, are an emerging technology and are used in textiles, plastics and all other foldable displays and wearable devices.
“Now, in bendable cell phones or wearable devices like health monitoring devices on textiles...the mechanical or electrical stress causes a fracture at the interconnect, thereby causing system failure. What we have done, to explain in a crude manner, is to mix metallic particles in oil and contain them over the interconnects. This mixture will help heal fractures in a matter of seconds,” Sambandan explained.
He said that there is no external control applied to achieve this and that the system need not specially act to trigger healing.
“The physics of the interaction of particles with the field results in knowing the interconnect is broken resulting in an automatic start and stop of healing. We’ve used 1 micron particles of silver in silicone oil. This material is smeared all over. It is engineered in such a way that the oil only stays in certain regions (interconnects),” he explained.
How does the self-healing work: When the interconnect breaks, the current it was carrying goes down to zero, but there will be a voltage causing an electric field. This electric field triggers self-healing.
“The electric field will polarise all the metallic particles and they attract each other and form a little chain/bridge across this gap. Once this is done, the current is restored. And, once the current is restored it heats all these loosely held particles and they stick together. Soon as the repair is done, the self-healing stops automatically,” Sambandan said.

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