“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. 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 liquid metal 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