The space elevator—a theoretical mode of transportation where transport modules move up and down a long cable that connects Earth to space—has long been the stuff of futuristic fantasy. It's shown up in books, movies, and scientific journals, while researchers have tried to uncover a material strong enough and light enough to make such a structure possible. Now, a team of MIT scientists has designed one of the strongest lightweight materials in existence, taking us one step closer to realizing that sci-fi dream—and creating a formula for a material that could revolutionize architecture and infrastructure right here on Earth, too.
The material is composed of graphene, a two-dimensional form of carbon that's considered to be the strongest of all known materials. But because the 2D form of graphene is so thin—it's only one atom thick—it's impractical for building purposes. The team's breakthrough is in creating a 3D geometry out of graphene using a combination of heat and pressure. As detailed in a paper published today in the journal Science Advances, they developed computational models of the form and then recreated it with graphene. The kicker? During testing, they found that the samples of the porous material were ten times stronger than steel, even though they were only 5% as dense.
According to Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering, who was on the research team along with researchers Zhao Qin, Gang Seob Jung, and Min Jeong Kang, the idea behind reconfiguring graphene is similar to changing the form of a piece of paper: When you role a piece of paper into a tubular shape, for instance, it's much stronger than when it's flat or crumpled. Tubular forms are already used in architecture because of their strength—the Willis Tower, in Chicago, uses a tubular structural system.
"It’s a very innovative material because if we can produce the material in big amounts, we can use that to somehow substitute some of the steel used for construction and infrastructure," Zhao Qin says. "We could save a lot of labor to construct infrastructure and buildings because it is so light and so strong."
The material could also have a positive environmental impact in architecture. Its porous structure and large surface area could act as a filter for water or air—which has potential applications in building green structures. Because it's made of carbon, the material is chemically and mechanically stable. In the face of external environmental factors, like stronger storms and rising sea levels, these features could help make buildings more resilient.
But Qin believes that the potential applications for the material aren't limited to buildings on Earth. It's in shipping supplies into space to build space stations, or even colonies, that such a lightweight building material could dramatically reduce costs. When asked to speculate about how many stories a skyscraper built of this type of material might have, Qin instead pointed to the space elevator. A structure of three-dimensional graphene could potentially clear the Earth's atmosphere, even if many remaining constraints make this a more distant possibility.
Even more exciting is the fact that the porous geometry the team designed doesn't necessarily require the use of graphene, which Qin says is currently so expensive that it would be ultimately impractical for engineering use. Other forms of organic molecules, like polypeptide proteins, cellulose, or silk, could also potentially be transformed into a material with similar geometric properties. While this has implications for the building industry, these types of super-strong materials could have potential in a host of products, from medical equipment to cars. Qin says this line of inquiry is next on the team's agenda.
While the space elevator today remains a fantasy, this advancement in material science has brought stronger, lighter, and more resilient forms of architecture—and that sci-fi future—a little closer.