File this under ‘That shouldn’t be happening!’: Scientists have observed a metal self-healing, something that has never been seen before. If this process can be fully understood and controlled, we could be at the dawn of a whole new era of engineering.
A team from Sandia National Laboratories and Texas A&M University tested the metal’s resilience using a specialized transmission electron microscope technique of pulling 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 a vacuum.
Cracks caused by the type of stress described above are known as fatigue damage: repeated stress and movement that cause microscopic fractures, eventually causing machines or structures to break. Amazingly, after about 40 minutes of observation, the crack in the platinum began to fuse back together and repair itself before starting again in a different direction.
![Metal diagram](https://www.sciencealert.com/images/2023/07/MetalDiagram.jpg)
“This was absolutely stunning to see firsthand,” say materials scientist Brad Boyce of Sandia National Laboratories. “We certainly weren’t looking for it.”
“What we’ve confirmed is that metals have their own intrinsic, natural ability to self-heal, at least in the case of nanoscale fatigue damage.”
These are exact terms, and we don’t yet know exactly how this happens or how to use it. However, when you consider the cost and effort required to repair everything from bridges to engines to telephones, there’s no telling how much of a difference self-healing metals can make.
And while the observation is unprecedented, it’s not entirely unexpected. In 2013, materials scientist Michael Demkowicz of Texas A&M University was working on a study predict that this kind of nanocrack healing could happen driven by the tiny crystalline grains in metals essentially pushing their limits in response to stress.
Demkowicz also worked on this latest study, using updated computer models to show that his decade-old theories about the self-healing behavior of metal at the nanoscale matched what happened here.
That the automatic recovery process took place at room temperature is another promising aspect of the research. Metal usually required lots of heat to change its shape, but the experiment was conducted in a vacuum; it remains to be seen whether the same process will occur in conventional metals in a typical environment.
One possible explanation involves a process known as cold welding, which occurs at ambient temperatures when metal surfaces get so close together that their respective atoms become entangled. Usually thin layers of air or contaminants disrupt the process; in environments such as the vacuum of space, pure metals can be forced close enough together to literally stick.
“I hope this finding will encourage materials researchers to consider that materials, under the right conditions, can do things we never expected,” say Demkowicz.
The research has been published in Nature.