"Because we are using an interfacial material that we can modify by repeating sequences, we can fine tune the properties. We can make it very flexible and very strong at the same time."Melik Demirel, Penn State
Nature creates layered materials like bone and mother-of-pearl that become less sensitive to defects as they grow. Now, using biomimetic proteins patterned on squid ring teeth, researchers have created composite layered 2D materials that are extremely stretchable and resistant to breaking.
"Researchers rarely reported this interface property for the bone and nacre because it was difficult to measure experimentally," said Melik Demirel, chair in biomimetic materials and director of the Center for Advanced Fiber Technologies at Penn State.
Composite 2D materials are made up of atom-thick layers of a hard material, like graphene or a MXene — usually a transition metal carbide, nitride or carbonitride — separated by layers of something to glue the layers together. While large chunks of graphene or MXenes have bulk properties, 2D composites' strength comes from interfacial properties.
"Because we are using an interfacial material that we can modify by repeating sequences, we can fine tune the properties," said Demirel. "We can make it very flexible and very strong at the same time."
He noted that the materials can also have unique thermal conduction regimes, or properties, spreading heat more strongly in one direction than a direction at 90°. The researchers report this work in a paper in the Proceedings of the National Academy of Sciences.
"This material would be great for insoles for running shoes," said Demirel. "It could cool the foot and the repeated flexing would not break the insole." These 2D composites could also be used for flexible circuit boards, wearable devices and other equipment that requires strength and flexibility.
According to Demirel, traditional continuum theory does not explain why these materials are both strong and flexible, but simulations demonstrated that the interface matters. What apparently happens is that, with a higher percent of the material composed of the interface, the interface breaks in places when the material is under stress, but the material as a whole does not break.
"The interface breaks, but the material doesn't," said Demirel. "We expected them to become compliant, but all of a sudden it is not only compliant, but super stretchy."
This story is adapted from material from Penn State, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.