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Self-healing electronics capable to regain conductivity

By Damir Beciri
20 December 2011

sottos-white-mooreCurrent electronic devices are becoming faster and denser, but such complex circuitry is prone to reliability problems, and once one tiny circuit within an integrated chip breaks, the whole chip or even whole device is unusable. A team of University of Illinois engineers has developed a self-healing system capable to repair a cracked circuit by fast restoration of its electrical conductivity.

“In general there’s not much avenue for manual repair”, said materials science and engineering professor Nancy Sottos. “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.”

Relying on their previous research related to self-healing polymer materials, the researchers dispersed microcapsules on top of a gold line functioning as a circuit. When they induce the circuit to break, these microcapsules (which are as small as 10 microns) break open to fill in the gap in the circuit by releasing the gallium–indium liquid metal contained inside.

This process of self-repairing occurs in mere microseconds, and the researchers demonstrated that 90 percent of their samples healed to 99 percent of original conductivity, even with a small amount of microcapsules.

“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”, said aerospace engineering professor Scott White. “Everything prior to this has been on structural repair. This is on conductivity restoration. It shows the concept translates to other things as well.”

Since the microcapsules break only near the places where gap occurs, the repair occurs at the point of damage, while the rest of the microcapsules stay intact. Since it requires no human intervention or diagnostics, and it can be applied in small circuitry at micro-scale, the technology could be very useful in repairs of circuits where repair is impossible due to integrated circuitry.

However, there are a few downsides of this system. Aside the fact that indium is a relatively high-priced material widely used in LCDs, electrical components and glass coatings, we have to ask ourselves what do we gain with usage of this system in electronics? While it can prolong the longevity of high-end electronics, the use of indium as well as longer warranty will surely influence the price. Another problem is a very probable situation where the same region of a circuit becomes exposed to stress and prone to failure. Once the microcapsules are used in such an area, there are no backup capsules that could be used to fill the gap in the very same region.

The system could be very beneficial for use in aircrafts, where miles of conductive wire can cause a critical malfunction that is hard to pinpoint or fix during flights. Unlike the Smart Connector system we described a few days before this article, this technology is capable to react within microseconds and fix the automatically fix the broken circuitry.

University of Illinois researchers are planning to improve their system and explore other ways to use microcapsules to control conductivity and implement their findings into batteries in order to improve their safety and longevity.

For more information, read the paper published in the journal Advanced Materials named: “Autonomic Restoration of Electrical Conductivity”.

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