Researchers at the Harbin Institute of Technology in China have designed a new kind of smart coating that manages to be both soft and hard and can heal itself.
The new polymer has properties of self-repair, opening up the ability to fuse cracks and paper over scratches.
"This is the most desirable property combination in the current self-healing materials and coatings. We designed a self-healing coating with a hardness that even approaches tooth enamel by mimicking the structure of epidermis," Miss Yang, who leads a team of researchers at the Harbin Institute of Technology, told Inverse. "This is the most desirable property combination in the current self-healing materials and coatings."
This new material is far from the first smart coating, with previous research looking at both soft and hard coating options, according to a paper published Wednesday, in ACS Nano.
Yang and his co-authors shaped the material they developed after human skin, this way creating a polymer that is both self-healing and hard.
"A self-healing material, when carved in two parts, can go back together like nothing has happened, just like human skin," according to Yang.
Coating mimicks epidermis
When the thick outermost layer of skin, the epidermis, is damaged, cells from the softer layer underneath can go up to the top to heal the injury. They harden and become dead cells in the process to protect the live layers beneath. But our skin is not very stiff and certainly not as hard as tooth enamel.
However, teeth do not have the property of repairing themselves. Yang and his team have managed to create a material that embodies the best of both worlds, with a multilayer structure akin to skin to be able to imitate the self-healing process.
Yang and his co-researchers created the multi-layers using polyvinyl alcohol, a synthetic polymer that is used in everything from fishing to eye drops, and tannic acid, utilized to stain wood and clarify beer. The materials are both environmentally friendly.
Yang and his team talk about this as a “living” layer, and it acts like the live skin layered under your epidermis. The upper layers have high concentrations of graphene oxide, a hard substance also used in battery electrodes.
Self-healing can save energy
Yang says globally there seems to be a need for better self-healing materials. “Nowadays people always talk about environment and energy,” he says.
“A self-healing material can help save a lot of money and energy using a smart, environmentally friendly way. But the current self-healing materials and coatings are typically soft and wear out quickly. This can bring potential problems about the management of plastic waste.”
“The trick is to use artificial materials in nature’s way,” says Yang. “The multilayer structure is the key. By placing a hard layer containing graphene oxide on top of a soft layer, we create a smart hybridization you can get the most out of.”
According to Yang, this new material could solve the waste problems as well. This is because it comes closer than any predecessor to combining the flexibility of a soft coating and the durability of a hard coating. It has advantages because it does not have the short lifespan of the first one or the brittleness of the second one, combining in a way the best of both worlds.