“This shouldn’t happen!” section: Scientists have observed a never-before-seen healing process in metal. If this process can be fully understood and controlled, we can usher in a whole new era in engineering.

A team from Sandia National Laboratories and Texas A&M University tested the metal’s toughness using a proprietary transmission electron microscope technique to pull the ends of the metal 200 times per second. They then observed self-healing on an ultra-small scale in a 40-nanometer-thick piece of platinum suspended in vacuum.

Cracks caused by the deformation described above are known as fatigue damage: repetitive stresses and movements that cause microscopic tears that eventually cause machinery or structures to fail. Surprisingly, after about 40 minutes of observation, the crack in the platinum began to reconnect and repair before turning in the other direction.

“It was incredible to see it first hand,” said materials scientist Brad Boyce of Sandia National Laboratories. “We certainly weren’t looking for that.”

“We confirmed that metals have their own inherent natural ability to self-heal, at least in the case of fatigue damage at the nanoscale.”

These are the exact conditions, and we don’t yet know exactly how this happens or how we can take advantage of it. But when you consider the cost and effort required to repair everything from bridges to motors to telephones, it’s impossible to tell how self-healing metals can make a difference.

And while this observation is unprecedented, it’s not entirely unexpected. In 2013, Texas A&M University materials scientist Michael Demkovich worked on a study that suggested that this type of nanocrack healing could be due to small crystal grains inside metals actually changing their boundaries in response to stress.

Demkovic also worked on this latest work, using updated computer models to show that his decades-old theories about metal self-healing at the nanoscale match what’s going on here.

Another promising aspect of the study is that the self-repair process took place at room temperature. Normally, a metal needs a lot of heat to change its shape, but the experiment was done in a vacuum; It is not yet clear whether the same process would occur with base metals in a typical environment.

One possible explanation lies in a process known as cold welding, which occurs at ambient temperature in which metal surfaces are brought close enough together that their corresponding atoms will mix. As a rule, the process is hindered by thin layers of air or pollution; In environments such as outer space, pure metals can be pressed close enough together to literally stick together.

“I hope this discovery encourages materials researchers to believe that under the right conditions, materials can do things we never expected,” Demkovic says. Study published Nature.