US researchers have created a ‘self-healing’ circuit board, a development that could have big implications for space travel
The vision of a physically ‘self healing’ computer moved one step closer this week after researchers in America created a system that restored electrical conductivity to a cracked circuit.
The discovery was made by a team of University of Illinois engineers in addressing one of the greatest weaknesses of the modern computer, namely that, if a tiny crack or failure occurs in a single circuit, often the entire board or indeed the whole computer itself is rendered useless.
The fault is often so tiny that repairs are often impractical and simply too costly. The problem is even worse when the device cannot be accessed to make the repair or install a replacement part.
The engineers have come up with a novel solution to the problem, as their self-healing circuit is able to repair itself when it is cracked by releasing liquid metal, which restores conductivity “in less time than it takes to blink.”
Potentially, the idea has far-reaching implications for sectors where any electronic failure would be disastrous. One obvious area for this would be space travel, or any other sector that uses computers in hazardous conditions, such as military applications.
The research was led by aerospace engineering professor Scott White and materials science and engineering professor Nancy Sottos, and the researchers published their results in the journal Advanced Materials.
“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.”
The researchers point out that a current problem is that manufacturers are increasing the density of a chip or circuit board. This increased density poses 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,” the researchers said.
“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.”
The researchers also point out a green angle for this discovery. With faulty consumer electronics simply being scrapped, electronic waste increases massively on a global scale. The self-healing circuitry would reduce this because it could deliver longer lasting electronic goods.
How did the researchers come up with such a simply but innovative idea?
Apparently, the boffins had already developed a system for self-healing polymer materials. They then decided to adapt their technique for conductive systems.
The process disperses tiny microcapsules, as small as 10 microns in diameter, on top of a gold line functioning as a circuit. When a crack develops, the microcapsules break open and release the liquid metal contained inside. The liquid metal flows into 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.”
The researchers said that a failure interrupts current for mere microseconds as the liquid metal immediately fills the crack. The team has demonstrated that 90 percent of their samples healed to 99 percent of original conductivity, even with a small amount of microcapsules.
Another advantage of this system is that repairs are localised to the fault only. “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,” said the researchers.