Nature-inspired protein creates stretchable, composite layered materials

July 25, 2022

By A’ndrea Elyse Messer

Using biomimetic proteins patterned on squid ring teeth, researchers have created composite layered 2D materials that are resistant to breaking and extremely stretchable.

Editor’s note: This article originally appeared on Penn State News. It features Melik Demirel, Lloyd and Dorothy Foehr Huck Chair in Biomimetic Materials, director of the Center for Advanced Fiber Technologies and professor of engineering science and mechanics, Penn State.

UNIVERSITY PARK, Pa. — Nature creates layered materials like bone and mother-of-pearl that become less sensitive to defects as they grow. Now, a Penn State-led research team has created — using biomimetic proteins patterned on squid ring teeth, circular appendages on the tentacles of squid that are used to grasp prey — composite layered 2D materials that are resistant to breaking and extremely stretchable. The results of this work were published today (July 25) in the Proceedings of the National Academy of Sciences.

"Researchers rarely reported this interface property for the bone and nacre because it was difficult to measure experimentally," said Melik Demirel, Lloyd and Dorothy Foehr Huck Chair in Biomimetic Materials and professor of engineering science and mechanics 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 other layers that interface with the hard material to glue everything 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, who also directs the Penn State Center for Advanced Fiber Technologies. "We can make it very flexible and very strong at the same time."

He noted that the materials can also have unique thermal conduction properties capable of spreading heat in one direction more strongly than at 90 degrees.

"This material would be great for insoles for running shoes," Demirel said. "It could cool the foot and the repeated flexing would not break the insole."

He also noted that these 2D composites could 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."

Others working on this project from Penn State were Mert Vural, postdoctoral fellow; Tarek Mazeed, postdoctoral fellow; Oguzhan Colak, graduate student; and Reginald F. Hamilton, associate professor; all in the Department of Engineering Science and Mechanics.

Dong Li and Huajian Gao, professors of mechanical and aerospace engineering at Nanyang Technological University in Singapore, also contributed to this work.

The Defense Advanced Research Projects Agency; the Army Research Office; Nanyang Technological University; and the Agency for Science, Technology and Research, Singapore, supported this work. Calculations were done at the A*STAR Computational Resource Centre, National Supercomputing Centre, Singapore.


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