Researchers from MIT have developed a form of graphene that is not only 10 times as strong as steel but also has just 5 percent of its density.
In a study published in the journal Science Advances, Markus Buehler and colleagues showed how fusing and compressing graphene flakes gave birth to the new material and addressed some of graphene's glaring weaknesses.
Graphene has always been strong - the strongest of all known materials - but the kind of strength it has in two-dimensional form does not carry over when the material is formed in 3D. The study addressed this problem. Instead of changing something in graphene, the researchers realized that the solution lay in how the material is used: formed in an unusual geometric pattern.
This also suggests that other strong and lightweight materials can be made stronger as well by taking on similar geometric features.
Earlier studies have explored strengthening lightweight materials but experiments were not able to match predicted results. For the current study, the researchers decided to analyze graphene down to individual atoms in its structure and they were able to come up with a mathematical framework that closely matched observations in their experiments.
Combining heat and pressure, the researchers were able to compress graphene flakes, creating a strong, stable structure similar in form to microscopic creatures known as diatoms and certain corals. With a surface area enormous compared to its volume, the structure was proven to be remarkably strong.
"Once we created these 3D structures, we wanted to see what's the limit - what's the strongest possible material we can produce," said Zhao Qin, one of the study authors.
The researchers produced different 3D models in the process, which they all subjected to tests. In computational simulations, it was the graphene sample that resulted in a material that had 10 times steel's strength but had just 5 percent of its density.
Graphene is just an atom thick but the geometry that gave its new form strength without added heft can also be used on large-scale structural materials, according to the researchers. For instance, concrete for structures like bridges can take on porous geometry to give it a boost in strength at just a fraction of added weight. As the form features airspaces within, it may also be used to improve insulative properties or as part of a filtration system for either chemical or water processing.
Recently, graphene also made news after researchers from Trinity College Dublin combined the material with Silly Putty to create a sensor that is sensitive enough to measure footsteps from spiders.
Called G-putty, the new material dramatically changes in electrical resistance with the slightest deformation or pressure. Specifically, just compressing or stretching it by 1 percent of its usual size will result in a shift in electrical resistance by a factor of five.
If other materials that can detect deformations were compressed or stretched at the same rate, just a 1-percent change in electrical resistance will be observed. This means G-putty has a sensitivity level 500 times better than these materials.