Be sure to check out part 2 of this 5-part series: “5 Reasons Drones Will Soon Be Everywhere,” and check back next week for part 4!
Graphite is, so far as we can tell in our daily lives, not the sturdiest stuff. That’s precisely why it’s useful for writing and used as the “lead” in pencils, after all. A little pressure, and it crumbles. So if you were to peel away a single layer of graphite, a sheet of interlocking hexagons of carbon a single atom thick… Intuitively, what properties would you expect it to have?
You probably wouldn’t expect it to be strong. You almost certainly wouldn’t expect it to be stronger than steel, much less many times stronger than steel. It definitely doesn’t sound like a good candidate for the strongest material known to man.
But as it turns out, it is. It’s called graphene, the first in a growing category of what are called 2D materials.
Some elements can exist in multiple forms, called allotropes – different ways of arranging atoms of an element that can result in very different properties. The same carbon atoms can be graphite or diamond, depending on how they’re arranged. As it turns out, when you put elements like carbon, silicon, tin, and others in crystalline patterns only one atom thick, their properties become very different indeed. They’re not literally two-dimensional, but they’re about as close as you can get. A graphene sheet is about 0.345 nanometers thick, or a bit more than one-third of one-billionth of a meter.
Graphene’s existence has been known for some time, but it was not until 2004 that it was first successfully isolated from graphite by Professors Kostya Novoselov and Andre Geim at the University of Manchester. It’s now being joined by a growing host of other 2D materials including silicene (2D silicon), phosphorene, (phosphorus,) stanene (tin,) and more.
Some, like graphene, have truly extraordinary properties. Tensile strength 200 times greater than steel combined with high flexibility, astonishingly high conductivity, tremendous energy storage capacity, and more. They have the potential to immensely advance everything from construction materials to electronics to energy to medicine.
Computers more powerful than anything made from today’s materials ever could. Powerful new treatments for cancer. Direct connections between machines and the human mind. Cell phones and tablets you can roll up like paper. Tennis rackets of terrifying speed and power. Unbelievably cool and efficient electrical wires. Electric cars you can recharge as quickly as you fill a gas tank today. Sophisticated electronics small and flexible enough to be built into your clothes. Sturdier, safer, more fuel-efficient vehicles. Nigh-unstoppable cyborg supermen. Sadly, I’m pretty sure jokes about how demanding Crysis is are well past their sell-by date at this point, or I’d throw that in too.
It’s early days yet, so discussion of uses for graphene and other 2D materials is still long on speculation and short on practical experience. And creating these materials is still a very difficult and expensive process, though it’s getting easier. Some scientific predictions about the expected properties of newer 2D materials, like stanene’s status as the world’s most conductive material, have not yet been proven empirically. So we don’t know just what’s possible with 2D materials yet.
But there’s a hell of a lot that might be. Here are five ways that graphene and other 2D materials can be put to astonishing use.
The most immediately striking feature of graphene is that it is light and flexible, yet astonishingly strong – 200 times stronger than the strongest steel. (Assuming equal thickness.) This could make it tremendously useful as a structural material when you want the most strength for the least weight. Graphene is unlikely to be used alone. Rather, it would be incorporated into composites to lend its strength to other materials, such as plastic or metal. This is both cheaper – anything made of pure graphene would be absurdly expensive – and can give the composite desirable attributes graphene would lack on its own.
Graphene could have a tremendous impact on vehicle construction, since maximizing the strength of a vehicle is highly desirable but usually in direct conflict with speed, maneuverability, and fuel efficiency. Graphene composites could give the same or better strength as existing materials while weighing much less, improving both safety and fuel efficiency. Vehicle weight is an especially pressing concern in aircraft, but cars and other ground vehicles stand to benefit too.
In addition to being strong and light, graphene is very good at dispersing kinetic energy… A bulletproof vest incorporating graphene sheets could offer better protection than present ballistic materials like Kevlar or even the ceramic plates in modern military armor, while being much lighter and more flexible. The value of the latter two traits should not be underestimated. Many soldiers have suffered permanent, sometimes disabling injuries and chronic pain from the accumulated effects of hauling around 60-100 pounds of armor and equipment day after day.
Meanwhile, Bill Gates has donated $100,000 in research funding for the purpose of making graphene-strengthened condoms. The mean-spirited jokes about being mere nanometers thick practically write themselves.
Graphene is not without weaknesses. Its fracture toughness – the ability to resist suddenly fracturing into pieces under stress when cracks or flaws are already present in the material – is much more modest than its strength. Most sheets of graphene are made by joining multiple graphene patches together, and it’s not quite seamless, so some flaws come built-in. Those flaws will give way more easily than the rest of the sheet- and when they do, they rapidly spread through the graphene sheet like cracks in glass.
Pushed too far, a strong material without fracture toughness is in danger of turning into the guy at the office who’s there every day, doesn’t stop working from the moment he arrives to the moment he leaves, and is always the calm, steady, unshakable voice of reason… until the day he shows up at work with a chainsaw and a shotgun because Bob from Accounting has parked in his space five days in a row and by God that is the last time anyone will ever do that.
There are ways to mitigate this, and even flawed graphene can still support an absurd amount of weight for something an atom thick. But it’s important to remember that there is no perfect material that’s best at everything; every material has weaknesses.
Still, as disappointments go, learning that something you’d hoped would be 200 times stronger than the strongest steel might be a mere 100 times stronger in real-world conditions isn’t too hard to get over.
Graphene’s strength is the most touted quality when describing the remarkable properties 2D materials, but not necessarily the most important. The extremely high electron mobility of 2D materials like graphene, silicene, and phosphorene, combined with their compact size, give them tremendous potential in electronics.
We may be close to exhausting the computing potential of conventional silicon. One of the big factors in computing power is how small you can make your transistors, and we’re now reaching sizes (less than 10 nanometers) so small that quantum effects threaten to become a serious problem for silicon transistors. 2D materials could create transistors at sizes where normal silicon is no longer viable, taking computing power to levels that would otherwise be impossible. 2D transistors can be incredibly small – the smallest graphene transistor to date contains only 10 atoms.
However, graphene has a serious drawback. It lacks an energy band gap – a range of electron energy levels that are unable to pass through the material. This means that, without special modifications to what’s already a costly and difficult production process, it cannot be used as semiconductor. A semiconductor can’t just open its energy bands to every smooth-talking elementary particle that comes along- it has to be able to say no. Graphene conducts everything, so there’s no “semi.” This is a bit of a problem, since you need semiconductors for digital logic gates, and you need digital logic gates for… Well, almost everything people actually do with computers now.
Thus far, graphene transistors have been analog devices. Those certainly have their use, and fully analog computers are a thing – or at least they were a thing, back when a box of metal gears that could do multiplication problems was the state-of-the-art in computer technology. Not so much now.
Silicene and phosphorene do have band gaps, so they’re probably better candidates than graphene as a successor to 3D silicon for most computing tasks. That doesn’t make graphene useless for computers – there are specialized applications, like wireless communications, where analog graphene processors would work very well.
Meanwhile, all those transistors need electricity to run and communicate. Computer components too small to see still get their electricity the old-fashioned way, with copper wires. Very, very, tiny copper wires. Unfortunately, as copper wires get narrower their electrical resistance goes up, increasing power consumption and waste heat. The more densely packed transistors get, the bigger a problem this becomes.
Enter stanene, two-dimensional tin. Stanene is believed to be – it wasn’t actually produced until 2015, so we’re not sure yet – the most efficient conductor of electricity on earth. Stanene is a topological insulator, which means electrons move along the material’s edges in a smooth, orderly fashion instead of bouncing around through the interior losing energy and creating waste heat. It’s like the janitor at my elementary school that always shrieked like a banshee if anyone wasn’t standing in line properly, except actually effective.
Stanene retains its conductive properties across a wider range of temperatures than other topological insulators, making it better for hot environments like the nightmarish sweatshop that is a computer processor. Nanoscale stanene wires could transmit electrical signals inside a computer chip with unparalleled efficiency, preventing your superfast silicene CPU from erupting into molten slag and burning a China Syndrome-esque hole through the crust of the earth.
No amount of fancy gadgetry will help you without power to run it. Luckily, graphene may be able to lend a hand there as well. Experimental lithium-ion batteries containing graphene can hold more energy than conventional counterparts, and have much faster charging times. Graphene’s optical and electrical properties make it, or perhaps its cousin graphene oxide, a promising material for solar panels. Perhaps most interesting, though, is what it could do for capacitors.
Like batteries, capacitors contain energy. They can be charged and discharged much faster than a battery, and can withstand many more such cycles, at the cost of much lower energy capacity for a given size. Somewhere between the two are supercapacitors, originally known as electric double-layer capacitors and also sometimes called “ultracapacitors.” (I assume it’s only a matter of time before Super Capacitor Turbo Championship Edition reaches the market.) These run at lower voltages than regular capacitors but can hold much more energy, though still much less than a battery. Usually.
That’s where graphene comes in. The chief factor in how much energy a supercapacitor can hold is the surface area of its electrodes. Consequently, these electrodes are made of materials that maximize their surface area for a given mass and volume. “Activated” carbon processed to be filled with tiny pores has long been used for this. More recently carbon aerogel, an incredibly light, porous, and misleading material that is actually neither air nor a gel, has come into use.
Graphene is an excellent conductor of electricity, far better than activated carbon. And if you want to maximize surface area, graphene is nothing but surface area! A capacitor using graphene sheets could contain more energy than anything in existing capacitors, and discharge that energy faster. There are already experimental graphene capacitors whose energy capacity per kilogram is actually comparable to a lithium-ion battery.
Capacitors with such tremendous energy capacity could have some striking effects. Portable devices like phones and laptops could be recharged almost instantly. Electric cars would become a much more appealing prospect – with an adequate power source you could “refuel” it in minutes instead of hours, and do so many more times before needing a replacement compared to a battery.
And all those electronic “I’m with Stupid” shirts certainly won’t power themselves.
Graphene has number of potential medical uses. Some would depend on its superior strength. Graphene could be incorporated into artificial bone and used in bone grafts for victims of severe skeletal injuries. (Or possibly to just give someone a nigh-unbreakable superskeleton, provided you can find a candidate with sufficiently powerful mutant healing abilities to survive the process.)
It would also aid in delivering drugs to a patient’s body. The active chemicals in a drug that actually cause its effects are often attached to other substances that help them reach their destination and provide maximum effectiveness. (Try to ignore any unfortunate mental images of microscopic drug mules smuggling contraband substances in their various orifices that this concept may have conjured up.) Graphene’s surface area allows it to carry the maximum possible payload, since it’s hard to increase the number of atoms in a substance exposed to the outside higher than “all of them.”
Graphene could be especially valuable in treating cancer. Like any other cell, cancer cells need to receive nutrients and dispose of waste via the body’s circulatory system, which tumors tap into like neighbors stealing cable. Shockingly, malfunctioning rogue cells that spread and reproduce wildly without regard for the well-being of their surrounding tissues don’t always do the best construction job. So tumor circulation tends to be… Well, pretty much what you’d expect a sanitation system built in haste by selfish, amoral hooligans to be like.
It doesn’t properly filter incoming molecules, so it’s easier for nanoparticles to get in, and once they’re in they accumulate because of poor waste drainage. Consequently, nanoparticles – like, just to choose an example completely at random, tiny ribbons of graphene – disproportionately accumulate in tumors rather than healthy tissue, making them an excellent way to deliver cancer-killing drugs without carpet bombing the rest of the patient’s body in the process.
Also, Bill Gates has donated $100,000 for research into using graphene to strengthen condoms. I know I already mentioned this, but since I have the maturity of a 10-year-old I wanted to seize this excuse to mention it again.
2D materials offer other possibilities for electronics beyond greater computing power. You could, for instance, trade in your night vision goggles for a pair of contact lenses.
An ultrathin infrared radiation detector can be made from two graphene sheets, with an insulating layer between them. When light hits the top sheet, its effects on the electrons there produces an electric field that affects the flow of an electrical current that is run through the bottom sheet. These changes are then measured and interpreted as visual data, letting you see thermal energy.
This allows infrared sensors that are thinner than is otherwise possible, and would function at room temperature without the cooling system some forms of infrared sensing require. Aside from better-known applications of infrared vision – surveillance, the military, tracking your quarry through the Central American jungle in your quest to make trophies of men – compact infrared sensors would also be a great boon for science, engineering, and perhaps especially medicine.
Graphene’s high conductivity, combined with the fact that it is nearly transparent, would also make it a good candidate for display technology using liquid crystals or light-emitting diodes. Now, recall that one of graphene’s striking properties is combining great strength with excellent flexibility.
Combined with processors based on 2D materials (whether graphene or something else,) this raises the possibility of electronic devices that are not only very compact or powerful, but bendable. Imagine having a smartphone, tablet, or laptop that could be bent like plastic, or even folded or rolled up like paper, without damaging it. You might even incorporate electronics into clothing.
(My first thought was that you could have an “I’m with Stupid” shirt that keeps track of where your companion is and makes sure the shirt’s arrow is always pointed in the appropriate direction. Fortunately, the world is full of people more creative and less malicious than I who could doubtless come up with good uses for such a technology.)
Maybe that’s not enough. Maybe you’d like to be a terrifying fusion of man and machine. Or at least be able to walk and pick stuff up, a much more modest request that thousands of victims of violence, accidents, and disease are still denied.
Great advances in technology for prosthetic limbs have been made possible by implanting electrodes and electric sensors directly into the brain. This allows the brain’s motor control center to send commands to an artificial limb, controlling it by thought just as it would a real body part. Information can also be sent in the other direction, with electrodes implanted in the sensory areas of the brain stimulating sensations such as sight or touch based on data from external sensors.
Graphene is a promising component for these implants, thanks to its strength, electrical conductivity, and transparency. Rigid conventional materials used in brain implants often produced scarring that impedes implants’ ability to interact with the brain over time, a problem that more flexible graphene could reduce.
Now, the first use for graphene neural implants would doubtless be medical. Prosthetic limbs for amputees that not only move but actually feel, cameras feeding images directly into the brains of the blind, perhaps artificial linkages between the brains and once-paralyzed limbs of paraplegics and quadriplegics.
We might, eventually, get a bit more ambitious. Consider the possibilities we’ve looked at. Suppose they’re realized – they may or may not all pan out, but none of them are wildly implausible.
We’ve got ultra-advanced sensors both inside and outside the body. We’ve got light, flexible material far stronger than steel, never mind the flimsy crap humans are built from. We’ve got powerful computers that barely take up any space. We’ve got two-way communication between organic brains and electronic devices. We’ve got very dense, easily rechargeable power sources.
We’ve basically got at least half the Deus Ex: Human Revolution upgrade tree. God have mercy on us all.
Be sure to check out part 2 of this 5-part series: “5 Reasons Drones Will Soon Be Everywhere,” and check back next week for part 4!