MIT researchers develop strong, lightweight material configuration

A team of MIT researchers have designed a new 3D graphene configuration. The team was able to compress and fuse together flakes of graphene to make a sponge-like configuration that is both strong and lightweight.

3D-printed gyroid models such as this one were used to test the strength and mechanical properties of a new lightweight material. Photo courtesy of Melanie Gonick/MIT

In its 2D form, graphene is thought to be one of the strongest materials. However, researchers have struggled with taking the 2D form and translating it into 3D materials.

The research team at MIT have managed to structure the graphene into a 3D form and discovered that the material’s strength and lightweight features have more to do with the geometrical configuration than the material itself.

The MIT team analyzed the material’s behavior down to the level of individual atoms within the structure. They were able to produce a mathematical framework that closely matches experimental observations.

The 2D materials have exceptional strength and unique electrical properties. However, due to their thinness, “they are not very useful for making 3D materials that could be used in vehicles, buildings, or devices,” says Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering (CEE). “What we’ve done is to realize the wish of translating these 2D materials into three-dimensional structures.”

The researchers compressed small flakes of graphene using heat and pressure. This produced a strong, stable structure with a  form that resembles some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be extremely strong.

“Once we created these 3D structures, we wanted to see what’s the limit — what’s the strongest possible material we can produce,” says Zhao Qin, a CEE research scientist.

The team created a variety of 3D models and used computational simulations to test the structures. The 3D graphene material proved both extremely strong and light weight. Buehler explains that this model resembled what would happen with sheets of paper.

Paper has little strength along its length and width, and can be easily crumpled up. But when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.

“You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” Buehler says, to gain similar advantages of strength combined with advantages in cost, processing methods, or other material properties (such as transparency or electrical conductivity).

“You can replace the material itself with anything,” Buehler says. “The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”

This illustration shows the simulation results of tensile and compression tests on 3D graphene. Photo courtesy of Zhao Qin.

The team expects a wide range of applications for their discovery. One possibility is to use the polymer or metal particles as templates, coat them with graphene by chemical vapor deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3D graphene in the gyroid form.

The same geometry could even be applied to large-scale structural materials, the team suggest. Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing.

“This is an inspiring study on the mechanics of 3D graphene assembly,” says Huajian Gao, a professor of engineering at Brown University, who was not involved in this work. “The combination of computational modeling with 3D-printing-based experiments used in this paper is a powerful new approach in engineering research. It is impressive to see the scaling laws initially derived from nanoscale simulations resurface in macroscale experiments under the help of 3D printing,” he says.

This work, Gao says, “shows a promising direction of bringing the strength of 2D materials and the power of material architecture design together.”

www.mit.edu