The concept is pretty simple. The team crushed up a bunch of neodymium permanent magnets, like the kind you find in electric motors and hard drives, into microscopic particles. It then inserted them into the ink used to make printed electronics, along with carbon powder to increase conductivity. The ink is then subjected to a magnetic field, aligning the particles so that when it's torn or cut, each side is magnetically attracted to the other, healing the breach.

The team says the system repairs tears as wide as 3 mm, "a record in the field of self-healing systems." As shown in the video above, it can also self-heal multiple cuts. They add that unlike other systems, the magnetic ink is long-lasting, fast, works without any user intervention and shrugs off humid or hot conditions.

There is one big issue -- the cut ink traces still function electronically after healing, but the ink is no longer bonded, which could cause intermittent problems under heavily loading. However, the group plans to develop new self-healing ink recipes and test them using computer simulations. "Our work holds considerable promise for widespread practical applications for long-lasting printed electronic devices," says lead author Joseph Wang.