Scotch tape can work miracles. It seals envelopes, fixes torn pages, and secures wrapping paper with sticky precision. And in 2002 the ubiquitous adhesive aided in the discovery of some of this century’s most important nanotechnology.
Andre Geim, a physics professor at the University of Manchester’s School of Physics and Astronomy, asked one of his Ph.D. students, Da Juang, to create a thin sample by polishing a 1-inch graphite crystal. According to the New Yorker, when Juang returned a few weeks later with a speck of carbon in a petri dish, Geim laughed and told him to try again since there was nothing left. But a colleague noticed a sticky tangle of Scotch tape in the trashcan, its adhesive covered with silver graphite dust.
Geim folded and pressed together a piece of the tape, and placed it under the microscope to discover that the graphite layers were the thinnest that he had ever seen. By gently opening the tape, he was able to further peel layers apart. In doing so, he isolated the first two-dimensional material ever discovered.
Graphene is a single layer of carbon—one atom thick—arranged in a two-dimensional hexagonal lattice pattern. It is the lightest material known, and it is 100 to 300 times stronger than steel.
As its name suggests, graphene is extracted from graphite, the carbon material used in pencils. Carbon’s layers are weakly bonded, which is why graphite (made up of stacked layers of graphene) makes such an excellent writing medium. As a pencil is drug across paper, it sheds these layers and leaves a visible mark.
But it’s the conversion from three-dimensional material to two that makes graphene so extraordinary. It becomes a remarkable energy conductor. In graphite, the electrons associated with the carbon atoms interact with each other between the layers to stick the sheets together. But when the layers are separated, they’re able to move across the lattice structure freely and with extraordinary speed.
Geim’s team also found that grapheme had a remarkable “field effect,” meaning that its conductivity can be easily influenced (and thus controlled) by other electric fields. And its conductivity is rather astonishing—35% better than copper—and its electron transport is 1,000 times better than silicon. Graphene has been called, “the nanomaterial of the new millennium.”
Energy storage researchers have focused on optimizing the material’s unique architecture. In time, it may enable the construction of components for electronic devices, allowing them to become smaller, lighter, and more energy efficient.
However, there are also challenges to working with graphene. It is especially difficult to manufacture without tiny flaws. But energy storage researchers have discovered ways to capitalize on this issue within certain applications. In hydrogen fuel cells, for example, they’ve found that the tiny holes allow hydrogen gas molecules to pass through so that the Graphene layer works as a filter, protecting nanocrystals from larger oxygen, moisture, and contaminants that often degrade battery performance.
Graphene has sparked tremendous excitement, investment, and innovation. Scientists agree that extensive research remains to be done, but that the material shows exciting potential for energy storage, as well as an array of technological advances. Who knows? Someday it may make capacitors, lithium-ion batteries, and sensors ultra-efficient or serve as a catalyst for graphene-based fuel cells.
Recently, researchers at Brown University discovered that by wrinkling the material, they could increase the performance by 400% over flat graphene sheets, resulting in higher current densities for more efficient batteries.
“After crumpling and wrinkling, the graphene oxide is highly stretchable and flexible without breaking, and retains good electrical conductivity,” Professor Ian Wong told EE Times. “Such functionality could be useful for wearable multifunctional devices that can sense and respond to external stimuli, such as chemical detection.”
In order to control the wrinkling effect, Brown University researchers deposited the graphene on Shrinky Dinks, a polymer base—and common 1970s-era children’s activity—that shrinks in predictable amounts when heated. And, once again, a household item has inspired innovation.
What applications can you envision for graphene? What do you think the implications will be for the future of energy storage?