Engineers from the University of Illinois are developing circuits that will automatically fix themselves when their wires are broken. The self-healing system restores electrical conductivity to a cracked circuit in mere microseconds.

For such a magical-sounding concept, the method is actually pretty straightforward. The engineers place 10-micron microcapsules along the length of the circuit. The microcapsules are full of liquid metal, a gallium-indium alloy. If the circuit underneath the microcapsules cracks, the microcapsules break open and release the liquid metal inside. The liquid metal fills the gaps in the circuit and restores up to 99 percent conductivity.

The self-healing system has the added advantage of being localized and autonomous. There's no need to go through an entire device as the capsules repair only the point of damage. More importantly, the system doesn't need human intervention or diagnostics, saving more time and money.

The researchers see their system as being used primarily in extreme environments like aerospace or heavy industry. In these settings a broken circuit might result in catastrophic failure and there might not be enough time to look through every wire to find the fault.

"In general there's not much avenue for manual repair," says materials science and engineering professor Nancy Sotto.

"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 system can also be used in the consumer market with portable devices like mobile phones and batteries. The self-healing microcapsules can quickly fix broken laptops or tablets. The team is already looking at applying their system to batteries to improve their longevity.

The results of the study are published in the journal Advanced Materials.