• Scientists have witnessed the healing of the metal without any human intervention
• Airplanes, engines and even self-repairing robots could now be plausible ideas

The idea of ​​the indestructible killer robots may look like something straight out of the Terminator movie.

But they could soon become reality, since scientists have just witnessed the healing of the metal for the first time, without any human intervention.

A company based in the United States study overturned everything we thought we knew about metals by revealing that wear-and-tear cracks can actually repair themselves under certain conditions.

It’s a discovery that has the potential to revolutionize engineering, with the prospect of self-healing engines, planes and even robots on the horizon.

“It was absolutely stunning to watch first-hand,” said Brad Boyce, a Sandia National Laboratories scientist who led the study with Texas A&M University.

“What we have confirmed is that metals have their own intrinsic and natural ability to repair themselves, at least in the case of nanoscale fatigue damage.”

The metals that are currently used to build vital infrastructure such as bridges and airplanes experience a lot of stress and repeated movement that causes microscopic cracks to form over time.

While such fatigue damage typically causes machines to break, Boyce and his team witnessed the reduction of the 18nm nanometer-sized fracture.

This was a completely unexpected finding as the scientists only intended to assess how cracks would propagate through a 40nm thick piece of platinum when pressure was applied.

It was 40 minutes into the experiment when the damage reversed, as a “T-junction” crack merged together as if it had never been there in the first place.

Then, as pressure was applied, the crack grew back in a different direction, as scientists watched in amazement under the microscope.

“From the solder joints in our electronic devices to the engines in our vehicles to the bridges we drive on, these structures often fail unpredictably due to cyclic loading that leads to crack initiation and eventual fracture,” Boyce continued.

“When they fail, we have to deal with replacement costs, lost time and, in some cases, injury or loss of life. The economic impact of these failures is measured in the hundreds of billions of dollars each year for the United States.

“The cracks in the metals were never to get bigger, not smaller. Even some of the basic equations we use to describe fissure growth exclude the possibility of such healing processes.

While much remains unknown about self-healing, scientists believe a process known as cold welding may have played a role.

This can occur at the peak of metal fatigue, allowing bare metals to “join” when compressed on contact.

Their study comes 10 years after Michael Demkowicz of the Massachusetts Institute of Technology put forward a similar theory about self-healing metals.

He promoted the idea that nanocracks rely on the generation of crystal defects called “disclinations” to heal in metals.

In this study, the researchers also recognized that different crystal materials with different grain shapes and textures could be impacted in different ways.

Their nano-sized stage was primarily tested in oxygen-free conditions, so they believe there is an opportunity to explore vacuum-free conditions even further.

Mr Boyce continued: ‘The extent to which these results are generalisable will likely be the subject of further research.

“We show that this happens in nanocrystalline metals under vacuum. But we don’t know if this can also be induced in conventional metals in the air.

Ten years after his own study, Demkowicz praised this latest research and expressed his hopes for the future.

He said: “I hope this discovery will encourage materials researchers to consider that, under the right circumstances, materials can do things that we never expected.”