STARTS WITH A BANG — OCTOBER 7, 2021 These 5 recent advances are changing everything we thought we knew about electronics From wearable electronics to microscopic sensors to telemedicine, new advances like graphene and supercapacitors are bringing "impossible" electronics to life. Atomic and molecular configurations come in a near-infinite number of possible combinations, but the specific combinations found in any material determine its properties. Graphene, which is an individual, single-atom sheet of the material shown here, is the hardest material known to humanity, but with even more fascinating properties that will revolutionize electronics later this century. (Credit: Max Pixel) KEY TAKEAWAYS Graphene, a single-atom thick sheet of a carbon lattice, is the hardest material known to humanity. If a cheap, reliable, ubiquitous way of producing graphene and depositing it in plastics and other versatile materials were discovered, it could lead to a microelectronics revolution. Along with other recent developments in miniaturized electronics, laser-engraved graphene is transforming this science-fiction future into a near-term reality. Almost everything we encounter in our modern world relies, in some way, on electronics. Ever since we first discovered how to harness the power of electricity to generate mechanical work, we’ve generated devices large and small to technologically improve our lives. From electric lighting to telephones to computers and much much more, every single device that we’ve developed consists of only a few simple components stitched together in a wide variety of configurations. In fact, for over 100 years, we’ve relied on: a voltage source (like a battery), resistors, capacitors, and inductors, as the core of practically every device ever invented and utilized. Our modern electronics revolution, which relied on these four types of components plus — a little later on — the transistor, has brought us practically every item we make use of today. As we race to miniaturize electronics, to monitor more and more aspects of our lives and our reality, to transmit greater amounts of data with smaller amounts of power, and to interconnect our devices to one another, we quickly run into the limits of these classical technologies. But five advances are all coming together in the early 21st century, and they’re already beginning to transform our modern world. Here’s how it’s all going down. Graphene, in its ideal configuration, is a defect-free network of carbon atoms bound into a perfectly hexagonal arrangement. It can be viewed as an infinite array of aromatic molecules. (Credit: AlexanderAIUS/CORE-Materials of flickr) 1.) The development of graphene. Of all the materials that have ever been found in nature or created in the lab, diamonds aren’t the hardest ones anymore. Instead, there are six that are harder, with the hardest of all being graphene. Isolated by accident in the lab in 2004, graphene is a one-atom thick sheet of carbon, locked together in a hexagonal crystal pattern. Just 6 years after this advance, its discoverers, Andre Geim and Kostya Novoselov were awarded the Nobel Prize in physics. Not only is it the hardest material ever, with an incredible resilience to physical, chemical, and heat stresses, but it is literally the perfect atomic lattice. Graphene also has fascinating conductive properties, which means that if electronic devices, including transistors, could be made out of graphene instead of silicon, they could be smaller and faster than anything we have today. If you mixed graphene into plastics, you could transform your plastic into a heat-resistant, stronger material that also conducted electricity. Additionally, graphene is approximately 98% transparent to light, meaning it has revolutionary implications for transparent touchscreens, light-emitting panels, and even solar cells. As the Nobel foundation put it just 11 years ago, “Maybe we are on the verge of yet another miniaturization of electronics that will lead to computers becoming even more efficient in the future.” But only if other advances also occurred alongside this development. Fortunately, they have. Compared to conventional resistors, SMD (surface mounted device) resistors are smaller. Shown here compared to a match head, for scale, these are the most miniaturized, effective, reliable resistors ever created. (Credit: Berserkerus at Russian Wikipedia) 2.) Surface mount resistors. This is the oldest of the “new” technologies, and should be familiar to anyone who’s ever dissected a computer or cellphone. A surface mount resistor is a tiny rectangular object, usually made out of ceramic, with conductive edges on either end of it. The development of ceramics, which resist the flow of electric current but don’t dissipate power or heat up as much, enables resistors that are superior in a great many ways to the older, traditional resistors that were used previously: axially leaded resistors. In particular, there are enormous advantages that come along with these little resistors, including: small footprint on a circuit board, high reliabilities, low power dissipation, and low stray capacitance and inductiveness, that make them ideal for use in modern electronic devices, particularly low-power and mobile devices. If you need a resistor, you can use one of these SMD (surface mounted devices) to either lower the size you need to devote to your resistors or increase the power that you can apply to them within the same size constraints. The photograph shows the large grains of a practical energy-storage material, calcium-copper-titanate (CCTO), which is one of the world’s most efficient and practical ‘supercapacitors.’ The density of the CCTO ceramic is 94 percent of the maximum theoretical density. Capacitors and resistors have been thoroughly miniaturized, but inductors lag behind. (Credit: R. K. Pandey/Texas State University) 3.) Supercapacitors. Capacitors are one of the oldest electronics technologies of all, based on a simple setup where you have two conducting surfaces (plates, cylinders, spherical shells, etc.) that are separated from one another by a very small distance, with those two surfaces capable of holding equal and opposite charges. When you try to run current through a capacitor, it charges up; when you either turn your current off or connect the two plates, the capacitor discharges. Capacitors have applications from energy storage to quick bursts that release it all at once to piezoelectronics: where a change in the pressure of your device creates an electronic signal. Of course, manufacturing multiple plates separated by tiny distances on very, very small scales is not only challenging, but fundamentally limited. Recent advances in materials, and in particular, calcium-copper-titanate (CCTO), are enabling the storage of great amounts of charge in tiny volumes of space: supercapacitors. These miniaturized devices are able to charge and discharge a great many times before wearing out, can charge and discharge much more rapidly, and can store up to 100 times more energy-per-unit-volume than old-style capacitors. They are a game changing technology as far as miniaturized electronics go. The novel graphene design for the kinetic inductor (right) has finally surpassed traditional inductors in terms of inductance density, as the central panel (in blue and red, respectively) demonstrates. (Credit: J. Kang et al., Nature Electronics, 2018) 4.) Superinductors. The last of the “big three” to be developed, superinductors are the newest player on the scene, having only come to fruition in 2018. An inductor is basically a coil of wire, a current, and a magnetizable core are all used together. Inductors basically oppose a change in the magnetic field inside of them, meaning that if you attempt to flow a current through one, it resists it for a time, then allows current to flow freely through it, and then resists the change once again when you turn the current off. Along with resistors and capacitors, they’re the three basic elements to all circuits, but, once again, there’s a limit to how small they can get. The problem is that the value of inductance depends on the inductor’s surface area, which is a dream-killer as far as miniaturization goes. But rather than classical magnetic inductance, there’s also the concept of kinetic inductance: where the very inertia of the current-carrying particles themselves oppose a change in their motion. Just like ants marching in a line have to “talk” to each other to change their speed, these current-carrying particles, like electrons, need to exert a force on one another to accelerate or decelerate, and that resistance to change creates kinetic inductance. Led by Kaustav Banerjee’s Nanoelectronics Research Lab, kinetic inductors that leverage graphene technology have now been developed: the highest inductance-density material ever created. Ultraviolet, visible, and infrared lasers can all be used to break apart graphene oxide to create sheets of graphene using the technique of laser-engraving. The right panels show scanning electron microscope images of the graphene produced at various scales. (Credit: M. Wang, Y. Yang, and W. Gao, Trends in Chemistry, 2021) 5.) Putting graphene in any device. Let’s take stock, now. We have graphene. We have “super” versions — miniaturized, robust, reliable, and efficient — of resistors, capacitors, and inductors. The last barrier to an ultra-miniaturized revolution in electronics, at least in theory, is the ability to transform any device, made of practically any material, into an electronic device. All we’d need to do in order to make this possible is to be able to embed graphene-based electronics into whatever sort of material, including flexible materials, that we desired. The fact that graphene is good mobility, flexibility, strength, and conductivity, all while being benign to human bodies, makes it ideal for this purpose. Over the past few years, the way graphene and graphene devices have been manufactured has come only through a small handful of processes that are themselves fairly restrictive. You can take plain old graphite and oxidize it, then dissolve it in water, and then fabricate graphene through chemical vapor deposition, but only a few substrates can have graphene deposited on them this way. You could chemically reduce that graphene oxide, but you wind up with poor-quality graphene if you do it that way. Or you could produce graphene via mechanical exfoliation, but that doesn’t allow you to control the size or thickness of the graphene you produce. If only we could overcome this last barrier, an electronics revolution might be close at hand. Many flexible and wearable electronic devices will become possible with the advance of laser-engraved graphene, including in the fields of energy controls, physical sensing, chemical sensing, and wearable and portable devices for telemedicine applications. (Credit: M. Wang, Y. Yang, and W. Gao, Trends in Chemistry, 2021) That’s where the advance of laser-engraved graphene comes in. There are two major ways that this can be accomplished. One involves starting with graphene oxide, as before: you take graphite, oxidize it, but then instead of chemically reducing it, you reduce it with a laser. Unlike chemically reduced graphene oxide, this makes a high-quality product, with applications for supercapacitors, electronic circuits, and memory cards, to name a few. You can also take polyimide — a high-temperature plastic — and pattern graphene directly onto it with lasers. The lasers break chemical bonds in the polyimide network, and the carbon atoms thermally reorganize themselves, creating thin, high-quality sheets of graphene. There have already been an enormous number of potential applications demonstrated with polyimide, since you can basically turn any shape of polyimide into a wearable electronic device if you can engrave a graphene circuit onto it. These include: strain sensing, Covid-19 diagnostics, sweat analysis, electrocardiography, electroencephalography, and electromyography, to name just a few. A number of energy control applications exist for laser-engraved graphene, including writing motion monitors (A), organic photovoltaics (B), biofuel cells (C), rechargeable zinc-air batteries (D), and electrochemical capacitors (E). (Credit: M. Wang, Y. Yang, and W. Gao, Trends in Chemistry, 2021) But perhaps what’s most exciting, with the advent, rise, and newfound ubiquity of laser-engraved graphene, is to look ahead to the horizon of what’s possible. With laser-engraved graphene, you could harvest and store energy: an energy control device. One of the most egregious example of where technology has failed to advance is the battery, as we pretty much store electric energy with dry cell chemical batteries, a technology that’s centuries old. Already, prototypes of storage devices such as zinc-air batteries and solid-state, flexible electrochemical capacitors have been created. With laser-engraved graphene, not only could we potentially revolutionize the way we store energy, but we could create wearable devices that convert mechanical energy into electrical energy: triboelectric nanogenerators. We could create superior organic photovoltaic devices, potentially revolutionizing solar power. We could create flexible biofuel cells as well; the possibilities are tremendous. On the fronts of both harvesting and storing energy, revolutions are on the short-term horizon. Laser-engraved graphene holds tremendous potential for biosensors, including the detection of uric acid and tyrosine (A), heavy metals (B), cortisol monitoring (C), the detection of ascorbic acid and amoxicillin (D), and thrombin (E). (Credit: M. Wang, Y. Yang, and W. Gao, Trends in Chemistry, 2021) Additionally, laser-engraved graphene should usher in an unprecedented era of sensors. This includes physical sensors, as physical changes, such as temperature or strain, can cause changes in the electrical properties, such as resistance and impedance (which includes contributions from capacitance and inductance as well). It also includes devices that detect changes in gas properties and humidity, as well as — when applied to the human body — physical changes in someone’s vital signs. The Star Trek inspired idea of a tricorder, for example, could quickly become obsolete by simply attaching a vital-sign-monitoring patch that alerts us to any worrisome changes in our bodies instantaneously. This line of thought can also open up a whole new field: of biosensors based on laser-engraved graphene technology. An artificial throat based in laser-engraved graphene can help monitor throat vibration, recognizing the differences in signals between coughing, humming, screaming, swallowing, and nodding motions. And, of course, if you want to create an artificial bioreceptor capable of targeting specific molecules, engineer all sorts of wearable biosensors, or even help enable a variety of telemedicine applications, laser-engraved graphene has tremendous potential. Laser engraved graphene has many wearable and telemedicine applications. Shown here are electrophysiological activity monitoring (A), a sweat-monitoring patch (B), and a rapid COVID-19 diagnosis monitor for telemedicine (C). (Credit: M. Wang, Y. Yang, and W. Gao, Trends in Chemistry, 2021) It was only in 2004 that a method for producing sheets of graphene, at least on purpose, was first developed. In the 17 years since, a slew of parallel advances has finally placed the possibility of revolutionizing how humanity interacts with electronics right on the cusp of the cutting edge. Compared to all prior ways of producing and fabricating graphene-based devices, laser-engraved graphene allows simple, mass-producible, high-quality, inexpensive graphene patterning across a wide variety of applications, including on-skin electronic devices. In the relatively near-term future, it wouldn’t be unreasonable to anticipate advances in the energy sector, including energy control, energy harvesting, and energy storage. Alongside that, advances in sensors, including physical sensors, gas sensors, and even biosensors, are also right on the near-term horizon. The largest revolution will probably come in terms of wearable devices, including devices used for diagnostic telemedicine applications. To be certain, many challenges and barriers to this still remain, but these represent incremental, rather than revolutionary, improvements. As connected devices and the internet of things continue to take off, the demand for ultraminiaturized electronics is greater than ever. With the recent advances in graphene technology, the future, in many ways, is already here. © Copyright 2007-2021 & BIG THINK, BIG THINK PLUS, SMARTER FASTER trademarks owned by Freethink Media, Inc. All rights reserved.