The Graphene Corner
What is Graphene?
Graphene is the lightest material known. Produced in single sheets, it’s composed of carbon atoms bonded together in honeycomb-shaped lattice that’s just one atom thick. Hyper conductive and 100 to 300 times stronger than steel, it’s also incredibly cheap.
What’s Graphene Used For?
Discovered in 2003, up until a short time ago, no one knew what what to do with it. Now, it’s a bleeding-edge material that’s being combined all the time with all sorts of other substances to develop varieties of inventions, ranging from electronics to medical devices to energy efficiency devices. That’s why we’re introducing this mini-feature, “The Graphene Corner”, to keep up with all the innovations.
Can Graphene’s Ripples Generate Electricity?
Since graphene is only one atom thick, it’s essentially a two dimensional material. Now, while that sounds impossible, pieces of graphene actually move by themselves due to what’s called Brownian motion. That is, because carbon atoms in graphene are being bombarded by other wandering atoms, like those that make up air, as wells as carbon’s own fluctuations, graphene doesn’t sit still but ripples like the surface of the ocean.
University of Arkansas Physics professor Paul Thibado and his group of student researchers wanted to study the movement of graphene and placed sections of the material on a copper wire grid to observe the fluctuations under a scanning electron microscope. What the team ultimately discovered was that the ripples occurred naturally due to atoms vibrating in response to ambient temperature. Because graphene ripples fluctuate up and down (what’s called temperature-induced curvature inversion) by itself, it would be possible to use it to generate electricity. All that had to be done was to imbue the graphene with a negative charge and place it between two positive electrodes. As the graphene rippled, its movement would then generate an electrical current, at least theoretically.
But theoretically speaking, how much electricity could it generate? The graphene sample sections were a mere 10 microns across — about one eighth the width of a human hair — which means ripples were in the nanometer range, so the output might be 10 picowatts of electricity. That’s 1 picowatt = 10-12 watts.
While this aspect of graphene might not be suitable for generating grid-scale amounts of power, it might be better suited for medical implants or IOT technologies.
Nanoribbon Transistors — It Matters How You Slice It
If you cut a sheet of graphene so that it’s only a few atoms wide, you create a nanoribbon. Nanoribbons are extremely useful because while graphene sheets are highly conductive, when you slice out a nanoribbon it becomes a semiconductor — but that depends on how you slice it.
Graphene consists of equilateral carbon hexagons. How the graphene nanoribbon acts, either as conductor or semiconductor, depends on how the edge is cut. If the cut is made so that it preserves the hexagon shapes and leaves a zig-zag edge, then the ribbon will act like a metal. If the shapes are cut across so that the edge has arms or an “armchair” edge sticking out, then it will be a semiconductor. Consequently, researchers have been looking for a much easier way to create nanoribbons for use in building graphene transistors that could ultimately revolutionize current computing power.
In 2013, Standford researchers discovered a method of making graphene transistors by using DNA to grow nanoribbons and then assembling the transistor structures.
Most recently in November, researchers at Empa in conjunction with the Max Planck Institute for Polymer Research and University of California at Berkeley announced they had successfully grown nanoribbons just nine atoms wide with the desired armchair edging using specially prepared molecules and an ultra-high vacuum process. Using a scanning electron microscope, the ribbons were then assembled on a gold base one nanometer wide and up to 50 nanometers long. To increase the switching efficiency and reliability, hafnium oxide(HfO2) was used as the dielectric material. Using this method, the researchers created high-performance field-effect transistors using graphene nanoribbons.
Graphene —The Natural Enhancement to Spiderwebs
It sounds like something out of 1950s sci fi movie —feed spiders an experimental substance and they’ll take over the world!
Well, maybe not, but researchers at Italy’s University of Trento have been giving spiders graphene in their drinking water to see if it would affect the quality of their spider silk.
The answer is boy, does it! In fact, graphene-enhanced spider silk is five times stronger than normal. Strong enough to hold the weight of a person, tough enough to rival kevlar. It’s actually one of the strongest materials on the planet.
Incredibly, both graphene and carbon nanotubes were processed naturally by test spiders and these combined with the spiders’ protein used for making their web-spinning silk. The change isn’t permanent, however, as once the graphene is gone from the food supply, the spiders stop producing the hyper-strong silk.
According to the experiment’s leader, Nicola Pugno, graphene and carbon nanotubes could lead to a new class of “bionicomposites” for other biological applications.
Graphene’s Role in the Future of Healthcare
What about bone? Bone is mostly composed of collagen that makes it flexible but also contains calcium carbonate which makes it hard. With aging populations facing an increasing number of bone disorders, degeneration, and disease, the number of patients is expected to increase in coming years —primarily due to increases in obesity and poor physical activity. One possibility is the use of graphene as a scaffold, either by implantation or injection, to build or regenerate bone. In other words, instead of using an implant to repair a broken bone, a patient could regenerate or regrow their hip joint with their own bone that was reinforced with graphene nanocomposites. That reduces the possibility of allergic reaction to metallic implants, implant failure, and other complications.
Check out more technology innovations in our Technology Buzz series!