When we talk about materials’ ability to endure scratches and scrapes we frequently focus on toughness, referring to a material’s ability to withstand abrasion. That is because most materials are unable to heal themselves once damaged. A new coating for metal, developed by researchers at Northwestern University, breaks the mold — by, well, not breaking. Instead of showing permanent damage when it’s scratched, scraped, or cracked, the novel material is able to self-heal within seconds. The hope is that the novel coating could one day be used to stop tiny defects from turning into the kind of localized corrosion that causes big structures to fail.
“We made self-healing coatings on metal surface based on oil,” Jiaxing Huang, professor of Materials Science and Engineering at Northwestern, told Digital Trends. “The unusual part is that the oil coating does not drip, sticks very well, and at the same time can rapidly heal when scratched. Such coatings can protect metal surface from highly corrosive environment[s].”
The self-healing material was achieved by modifying an oil with lightweight hollow particles in the form of tiny graphene capsules, measuring just tens of microns in size. These capsules form a network in the oil, preventing the oil film from shrinking or dripping. However, they still allow oils to flow when a scratch breaks the network, thereby healing the damaged area. In a proof of concept demo, the researchers showed that the material is able to heal repeatedly. Even after being scratched in the exact spot for nearly 200 times in a row, it was still able to return to its former un-visibly damaged state within seconds.
But while Huang describes this as a “very interesting lab discovery,” he warns against overhyping the material. That’s because it’s so far only been demonstrated on small-sized samples, such as metal plates or on wires. Provided that there is no problem when scaling it up, though, one possible real-world application could include emergency underwater repair of coatings on metal structures — since the modified oil can be brushed directly onto metal underwater. It might also be useful as a temporary anti-corrosion solution for metals which are going to be placed into highly corrosive environments.
“We are interested in [the] anti-fouling properties of such coatings,” Huang said, describing possible next steps. “We also wish to broaden the scope of suitable lightweight particles or to find ways to mass produce such graphene capsules. This is such an intriguing, yet seemingly simple system [that] we wish to gain much better understanding of why it works so well.”
A paper describing this project was recently published in the journal Research.