Graphene is the super substance that could replace silicon, plastic and glass
By Marco Chiappetta
The silicon, plastic, and glass that make up much of our tech these days could soon be replaced with something old, yet completely new: Graphene.
If graphene sounds like something that could fell a superhero, you’re almost right. It’s the thinnest substance known to science, yet it’s 300 times stronger than steel and harder than a diamond. High-quality graphene is also transparent and flexible, and it’s an excellent conductor of heat and electricity.
We’ve known of graphene’s existence since the mid-1800s, but scientists have been able to experiment with graphene only in the past decade. In 2004, two researchers at the University of Manchester isolated graphene for the very first time, using—believe it or not—a chunk of graphite and a roll of adhesive tape.
So what exactly is graphene?
Graphene is a crystalline structure composed entirely of carbon atoms, arranged in a hexagonal, honeycomb-like pattern. Graphene’s single-atom thinness (meaning it has length and width, but no height) makes it as close to 2D as any substance can be.
Graphene is also a fundamental component of other allotropes (structurally different forms of the element carbon). These include charcoal, carbon nanotubes, and other fullerenes (molecules composed solely of carbon).
It is graphene’s unique structure and composition that endows it with so many valuable properties. Carbon atoms have four electrons in their outer shell, three of which form strong covalent bonds with the electrons in neighboring carbon atoms. This gives graphene its signature hexagonal shape. The fourth electron in each carbon atom, now known to be fermions, behave like relativistic particles described by the Dirac equation (which, in another sci-fi twist, also implies the existence of antimatter).
Getting back to graphene, it is those free electrons, in conjunction with the material’s relative uniformity, that make graphene such an excellent electrical and thermal conductor, superior to copper and silver respectively. The strong covalent bonds between the carbon atoms, meanwhile, give graphene its strength.
Layers of graphene are bonded by weak van der Waals forces (the sum of attractive forces between two surfaces, accounting for a lizard’s ability to climb vertical walls, among other things). The bonds between the carbon atoms in each layer of graphene, on the other hand, are incredibly strong; in fact, a hammock fabricated from a single-atom-thick sheet of graphene could support a load of nearly 9 pounds.
High-quality graphene is also lightweight, flexible, impermeable to other elements, and it’s virtually transparent. Thanks to the space between its atoms, the material absorbs just 2.3 percent of white light, allowing 97 percent to pass through.
How graphene might be used
Potential applications for graphene are nearly limitless. Numerous projects are already underway in industries ranging from consumer electronics to sporting goods. To date, graphene-based consumer products have been limited to items that use a small amount of the substance in protective coatings. Once the mysteries of graphene manufacturing have been unlocked—more on that later—you can expect to find the material everywhere.
One area where graphene is likely to have the most immediate impact is the manufacture of flexible and transparent electronics, such as touchscreens. Graphene could replace indium, which is one of the rarest elements on Earth. (Carbon—the foundation of graphene—is one of the most abundant elements on the planet.) Graphene is also lighter, thinner, and stronger than indium. Ultra-strong windshields that double as display clusters are not out of the realm of possibility. Neither is Tony Stark’s transparent smartphone.
Graphene’s electrical properties also render it an ideal material for building integrated circuits. During a Q&A session at the 2013 Intel Developers Forum, Intel CEO Brian Krzanich said the company is evaluating graphene’s potential use in chip manufacturing, replacing silicon. Routine use, he said, would be a “few generations” out, putting it roughly in the 2020 timeframe.
Graphene might also serve as the foundation for next-generation solid-state capacitors that charge more quickly than today’s offerings and hold a charge for much longer. And graphene could usher in an age of ultra-powerful, lightweight batteries with far more capacity than anything available today. By super-cooling graphene and surrounding it in strong magnetic fields, researchers have also been able to alter the direction of the flow of electrons along graphene’s surface, based on the spin of the electrons, which opens up possibilities for quantum computing.
Graphene won’t be relegated solely to electronics and display technology. Its excellent strength-to-weight ratio could also pave the way for strong, lightweight vehicles, while its transparency and electrical conductivity make it a good candidate for future solar panels. Punching nano-sized holes in a sheet of otherwise impermeable graphene could be used in machines that pull a single strand of DNA through the hole, for rapid DNA sequencing, or water purification or desalination.
Before those fantastical devices can become reality, however, industry must first develop a reliable, cost-effective manufacturing process. That’s where the majority of current graphene research effort is concentrated.
Graphene is being manufactured today using a number of methods: The “Scotch tape” method (also known as mechanical exfoliation or the cleavage method), is the simplest. This is how Andre Geim and Konstantin Novoselov isolated graphene from a larger hunk of graphite in 2004—research that led to their being awarded the Nobel Prize in Physics in 2010.
The adhesive tape is used to extract small pieces of graphite from a larger chunk. A layer of graphene is peeled away from the graphite by continually folding the tape over the pieces and then separating the tape. The strength of the adhesive overcomes the weak van der Walls forces holding the layers of graphite together until there is a single layer, yielding graphene.
Mechanical exfoliation can be used only to isolate relatively small pieces of graphene, however, so researchers are experimenting with other methods to produce larger quantities.
Chemical vapor deposition (CVD) is one of the most promising. In this process, chemical vapors are evaporated in a furnace, leaving a graphene deposit on a thin metal substrate. A similar process has been used in the manufacture of very large integrated circuits (VLSI) for many years. Graphene can also be isolated by submerging graphite in a liquid and blasting it with ultrasonic waves to separate its individual layers, or by slicing an edge of a cylinder formed from graphene (also known as a carbon nanotube).
Using these methods, scientists have been able to produce pieces of graphene of various qualities and sizes, including long graphene strands that have already been used to make super-capacitors. While some companies—most recently Samsung—have claimed breakthrough achievements in graphene manufacturing, most of the known work remains academic and has not yet scaled to real-world industrial applications.
We’re still a ways off from widespread availability of graphene-based microprocessors, flexible touchscreens, and similarly exotic new devices. But when industry perfects a practical and inexpensive means of manufacturing graphene, you can bet it will become as ubiquitous as plastics are today.
Image credits: The image at the top of this page is courtesy of Graphenea, a graphene manufacturer and supplier. The image of the graphite, adhesive tape dispenser, and graphene transistors was released by the copyright holder into the public domain.
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