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Reuters

In the 1991 film Terminator 2: Judgment Day, a malevolent time-travelling and shape-shifting android called T-1000 that was made of liquid metal showed a unique quality. Hit with blasts or bullets, its metal would heal itself.
Self-healing metal is still just science fiction, right? Apparently not.
Scientists on Wednesday described how pieces of pure platinum and copper spontaneously healed cracks caused by metal fatigue during nanoscale experiments that had been designed to study how such cracks form and spread in metal placed under stress.
They expressed optimism that this ability can be engineered into metals to create self-healing machines and structures in the relatively near future.


Metal fatigue occurs when metal sustains microscopic cracks after being exposed to repeated stress or motion, damage that tends to worsen over time.
It can cause catastrophic failures in areas including aviation – jet engines, for instance – and infrastructure, such as bridges and other structures.
In the experiments at the US government’s Sandia National Laboratories in New Mexico, the researchers used a technique that pulled on the ends of the tiny metal pieces about 200 times per second. A crack initially formed and spread. But about 40 minutes into the experiment, the metal fused back together.
The researchers called this healing “cold welding”.
“The cold welding process is a metallurgical process that is known to occur when two relatively smooth and clean surfaces of metal are brought together to reform atomic bonds,” said Sandia National Laboratories materials scientist Brad Boyce, who helped lead the study published in the journal Nature.
China scientists turn to ‘Terminator’ liquid metal in alloy breakthrough
“Unlike the self-healing robots in the Terminator movie, this process is not visible at the human scale. It occurs at the nanoscale, and we have yet to be able to control the process,” Boyce added.
Metal pieces were about 40 nanometres thick and a few micrometres wide. While the healing was observed in the experiments only in platinum and copper, Boyce said simulations indicated that self-healing can occur in other metals and that it is “entirely plausible” that alloys like steel could exhibit this quality.
“It’s possible to envisage materials tailored to take advantage of this behaviour,” Boyce said.
“Given this new knowledge, there may be alternative material design strategies or engineering approaches that could be devised to help mitigate fatigue failure. In addition, this new understanding may shed light on fatigue failure in existing structures – improving our ability to interpret and predict such failures,” Boyce added.

Scientists in the past have fashioned some self-healing materials, mostly plastics. Study co-author Michael Demkowicz, a Texas A&M University professor of materials science and engineering, predicted self-healing in metal a decade ago.
Demkowicz correctly figured that under certain conditions, putting metal under stress that ordinarily should worsen fatigue-related cracks could have the opposite effect.
“My guess now is that tangible applications of our findings will take another 10 years to develop,” Demkowicz said.
“When I first made my predictions, some of the press said I was working on a T-1000. That’s still sci-fi,” Demkowicz said.
Pangolin scales could be key to self-healing bulletproof vests: scientists
“However, at the end of television series] Battlestar Galactica, the crew adapted some Cylon [a fictional robot race] technology to help heal fatigue damage to their ship, making metal behave more like an organic tissue that can heal its own wounds. I’d say what we’re working on is more along the lines of the Battlestar Galactica example.”
The self-healing was observed in a very specific environment using a device called an electron microscope.
“One of the big questions left open from the study is if the process also happens in air, not just the vacuum environment of the microscope.
“But even if it only occurs in vacuum, it still has important ramifications for fatigue in space vehicles, or fatigue associated with subsurface cracks that are not exposed to atmosphere,” Boyce said.


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Science

Self-healing metal? It’s not just the stuff of science fiction

The T-1000 liquid metal robot played by Robert Patrick in the film Terminator 2. Image: Tri-Star Pictures

Green marks the spot where a fissure formed, then fused back together in this artistic rendering of nanoscale self-healing in metal, discovered at the US government’s Sandia National Laboratories. Image: Dan Thompson/Sandia National Laboratories via Reuters

Scientists create self-healing robots with 'Borg-like' ability to adapt to damage

An "injured" robot scrambles to its feet in a still from a video provided by  University of Wyoming researchers. Photo: SCMP Pictures

An "injured" robot scrambles to its feet in a still from a video provided by  University of Wyoming researchers. Photo: SCMP Picture

China scientists turn to ‘Terminator’ liquid metal in alloy breakthrough

Researchers at China’s Wuhan University say they have developed a method of creating exceptionally strong alloys at lower temperatures using a malleable metal called gallium. Photo: Shutterstock

The researchers used energy-dispersive X-ray spectroscopy to map the elements of the alloy during synthesis. Photo: Fu Lei

A schematic of the liquid metal-assisted alloying process. Photo: Fu Lei

Chinese researchers test metal alloy to fix broken bones in minutes

X-Ray shows image of the metal alloy after it's injected under human (a, b) and mouse skin (c)

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World

United States & Canada

Experiments show pieces of platinum and copper healing cracks caused by metal fatigue, an ability scientists say could be engineered into future machines
The process was observed at the US government’s Sandia National Laboratories in New Mexico


Experiments show pieces of platinum and copper healing cracks caused by metal fatigue, an ability scientists say could be engineered into future machines.


Science fiction

United States