With silicon pushed to its limits, which will drive the next electronic revolution

The semiconducting silicon chip ushered in the revolution in electronics and computerization that life was barely recognizable from the start in the first years of the 21st century. Integrated silicon circuits (ICs) support virtually everything we take for granted in our networked, digital world: they control the systems we use and allow us to freely access and share information.

The advances since the first silicon transistor in 1947 have been enormous: the number of transistors on a single chip has risen from a few thousand in the earliest integrated circuits to more than two billion today. Moore's law, which states that the transistor density doubles every two years, is still 50 years after it was proposed.

However, silicon electronics are challenged: the latest circuits are only 7 nm wide - between a red blood cell (7,500 nm) and a single DNA strand (2.5 nm). The size of single silicon atoms (by 0.2 nm) would be a hard physical limit (with an atom-wide circuit), but their behavior becomes unstable and difficult to control before.

Without the ability to continue shrinking ICs, silicon can not continue to produce the profits it has so far. To meet this challenge, we may need to rethink how we make equipment, or even whether we need an alternative to silicon itself.

Speed, heat and light

To understand the challenge, we need to examine why silicon has become the material of choice for electronics. It has many advantages - it is abundant, relatively easy to process, has good physical properties, and has a stable native oxide (SiO2) that happens to be a good insulator - it also has several disadvantages.

A big advantage of combining more and more transistors in a single chip, for example, is that an IC can process information faster. However, this speed boost crucially depends on how easily electrons can move within the semiconductor material. This is known as electron mobility, and while electrons in silicon are quite mobile, they are much more so in other semiconductor materials such as gallium arsenide, indium arsenide, and indium antimonide.

However, the useful conductivity properties of semiconductors involve not only the movement of electrons, but also the movement of so-called electron holes - the gaps left in the lattice of electrons revolving around the core after the electrons are expelled.

Modern ICs use a technique called Complementary Metal Oxide Semiconductor (CMOS) that uses a transistor pair, one using electrons and the other using electron holes. However, the mobility of electron holes in silicon is very low and this is an obstacle to higher performance - so much so that manufacturers need to increase it for several years by including germanium in the silicon.

The second problem with silicon is that its performance deteriorates severely at high temperatures. Modern ICs with billions of transistors generate significant heat, which is why they require a lot of cooling - think of the fans and heatsinks attached to a typical desktop computer processor. Alternative semiconductors such as gallium nitride (GaN) and silicon carbide (SiC) handle much better at higher temperatures, which means they can run faster and have begun to replace silicon in critical high-power applications such as amplifiers.

Finally, silicon is very bad at transmitting light. While lasers, LEDs, and other photonic devices are commonplace today, they use alternative semiconductor connections to silicon. As a result, two different industries have developed, silicon for electronics and compound semiconductors for photonics. This situation has existed for years, but now there is a great deal of effort to combine electronics and photonics on a single chip. That's a big problem for the manufacturers.

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New materials for the future

Of the many materials being studied as partners in improving the electronic performance of silicon, perhaps three are promising in the short term.

The first concerns the poor electron mobility of silicon. A small amount of germanium is already added to improve this, but it would be even better to use large amounts or even a switch to all-germanium transistors. Germanium was the first material used for semiconductor devices. So that's really a step back in the future. However, a reorientation of the established industry to germanium would be quite a problem for the manufacturers.

The second concerns metal oxides. Silicon dioxide has been used in transistors for many years, but with miniaturization, the silicon dioxide layer has shrunk to gradually lose its insulating properties, resulting in unreliable transistors. Despite the decision to use hafnium dioxide (HfO2) from rare earths as a replacement insulator, alternatives with even better insulating properties are being sought.

Perhaps most interesting is the use of so-called III-V compound semiconductors, especially those containing indium, such as indium arsenide and indium antimonide. These semiconductors have up to 50 times higher electron mobility than silicon. In combination with germanium-rich transistors, this approach could lead to a significant increase in speed.

Yet not everything is as easy as it seems. Silicon, germanium, oxides and the III-V materials are crystalline structures whose properties depend on the integrity of the crystal. We can not just throw them together with silicon and get the best out of both. The solution to this problem, the crystal lattice mismatch, is the biggest technological challenge.

Various flavors of silicon

Despite its limitations, silicon electronics have proven to be adaptable and can be converted to reliable mass market devices with minimal cost. Despite the headlines about the "end of silicon" or the spectacular (and sometimes rather unrealistic) promise of alternative materials, silicon is still king and will not be sold in our lives, based on a huge and extremely well-developed global industry.

Instead, advances in electronics are made by improving silicon through the integration of other materials. Companies like IBM, Intel and university labs worldwide have put a lot of time and effort into this challenge. The results are promising: a hybrid approach, mixing III-V materials, silicon and germanium, could be launched within a few years. Compound semiconductors have already found important applications in lasers, LED lighting / displays, and solar modules where silicon simply can not compete. Advanced connectivity is needed as electronic devices become smaller and smaller in power, as well as for high performance electronics where their properties greatly enhance the capabilities of silicon.

The future of electronics is promising and will still be largely based on silicon - but now there are silicon in many different flavors.

Why can not we repair our electronic devices ourselves?

When a car breaks down, the solution has traditionally been to repair it. Repair manuals, experienced mechanics and auto parts dealers make car repairs common, fast and relatively inexpensive. Even modern, computer-equipped vehicles have a lot to do with normal people: changing oil, changing tires, and many other advanced enhancements.

But when a computer or a smartphone breaks down, it's difficult to fix the problem, and more often the broken device is thrown away. Even small electronic devices can cause a huge amount of electronic waste - between 20 million and 50 million tons of electrical appliances per year worldwide. Part of this waste is recycled, but most - including components containing lead and mercury - are dumped in landfills.

Larger devices can be just as difficult to repair. Today's farmers are often unable to repair the computers on which their tractors are running, as manufacturers claim that farmers do not own them. Companies argue that special software used to run tractors and other machines is protected by copyright and patent laws. Granting farmers access to them would violate the intellectual property rights of companies.

The right of the users to repair their own objects or to pay others for it is endangered. However, in our product lifecycle surveys and research, my colleagues and I have found that providing support for those who want to repair and reuse their defective equipment can bring benefits - including benefits - to electronics manufacturers.

A corporate conflict

At least eight states-Nebraska, Kansas, Wyoming, Illinois, Massachusetts, Minnesota, New York, and Tennessee-are considering laws that oblige companies to have their defective electronics repaired by customers. The proposals usually cause manufacturers to sell parts, publish repair manuals and provide diagnostic tools, such as: B. Scanning devices that identify sources of error. In an encouraging move, the US Copyright Office suggested in June that similar rules should apply nationwide. And the US Supreme Court recently ruled that corporate patent rights do not prevent people from selling their electronics privately.

On the one hand, these regulations present a difficult task for the manufacturing companies. Manufacturers can make a lot of money selling authorized parts and service. However, to remain competitive, they must constantly innovate and develop new products. To keep costs down, they can not forever make and store parts for old and outdated equipment. This leads to the so-called "planned obsolescence", the principle that a company designs its articles with relatively short useful lives, which ends approximately at the time when a new version of the product comes out.

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However, our research suggests that companies can take a different approach - designing and manufacturing products that can be refurbished and repaired for reuse - while strengthening customer loyalty and brand awareness. When analyzing interviews with hobbyists and the repair industry, we also found that there are obstacles, such as: These include the lack of repair manuals and spare parts that can hinder and improve the growth of the repair industry.

CAlthough machines and equipment have become less mechanical and electronic, we expect that customers will continue to be able to repair and reuse the electronic products they have purchased. When manufacturers support this expectation by offering repair manuals, replacement parts, and other instructions for repairing their products, they build customer loyalty.

In particular, we have found that customers are more likely to buy additional products from this manufacturer and recommend this manufacturer product to friends. The math here is simple: more customers using a company's products, whether they are new or still in the marketplace after many years, mean more money for the company.

Our research also shows that the failure of most electronic devices is due to simple accidents such as falling or spilling water. The most common problem is a broken screen. There are also other problems - such as Batteries that no longer hold their charge, or printed circuit boards that just do not work anymore.

Simple repairs do not require much work or many tools. arrowsmith2 / Shutterstock.com

Even non-technical users often want to pay someone to clean their devices and replace parts like damaged screens and old batteries. If manufacturers give access to spare parts, more damaged parts could be repaired, which adds to their usefulness. Apple could seize an opportunity here: It's just started to assemble older iPhone models in India, meaning that parts are still being made that can repair other devices they already have.

Helping consumers, businesses and the environment

Technology manufacturers should take action to promote their customers' right to repair their defective equipment, which helps reduce electronic waste and strengthen brand loyalty. If this is not the case, laws and regulations can help.

For example, in France, a 2015 law requires manufacturers to tell customers how long spare parts are available before buying an item. So consumers can decide how much they want to include in the purchase decision for something new in the repair option.

Support for repair rights can not only bring economic benefits to the technology sector. In 1998, there were 4,623 consumer electronics repair and maintenance companies in the US. By 2015, this number had dropped to 2,072. Independent vendors are creating online marketplaces where users can buy and sell used and repaired equipment. Other companies, such as iFixit and Repair Cafe, are creating networks of people who exchange information to repair electronics and even bring together groups of people in person to work on their devices.

In the meantime, making spare parts for older devices through 3D printing is getting easier and cheaper.

However, businesses should not fear that people take too much in their hands: While it has been possible for some years to print and mount entire computers in 3D, they are not very good. The likelihood of buying company equipment is much higher. They only want to be able to repair them if they break.onsumers want to repair their equipment

What if your Fitbit could be powered by a Wi-Fi signal?

The new electronic 2-D technology can use radio energy to power a range of devices such as hearing aids, sensors and other devices that make up the Internet of Things

A flexible, flat semiconductor material that can extract energy from radio signals in cities could be just the thing for a new generation of electronics.

A team from the Massachusetts Institute of Technology reports in Nature that a film of molybdenum disulphide (MoS2) - a two-dimensional material because it's only three atoms thick - can act as an antenna to transmit radio signals from Wi-Fi, cell phones and radio or radio Radios convert television broadcasts to power for wireless devices. It could power energy-efficient pacemakers, hearing aids, and Internet of Things (IoT) sensors.

The power supply would not be enough to charge cell phones and tablets without dramatic breakthroughs, and even the Fitbit is a bit far away. But a small step towards Wi-Fi power can be at hand. "The future of electronics brings intelligence to every single object, from our clothing to our desks and our infrastructure," says Tomás Palacios, professor of electrical engineering at MIT. "The key missing component is how all these billions of devices can be powered." MoS2 sheets are promising because they are flexible and can be inexpensively produced in roll-to-roll printing.

The group demonstrated a flexible material that can cover radio energy at frequencies up to 10 gigahertz. It covers the widely used 2.4- and 5-gigahertz bands that transmit Wi-Fi signals as well as other radio traffic. Flexibility is important for portable devices and many other sensor applications, but other flexible materials generally absorb little radio power at frequencies above 1.6 gigahertz, limiting their potential for power generation. 

According to Palacios, the two-dimensional semiconductor can generate 30 to 50 microwatts of approximately 100 microwatts of WLAN ambient signals, which is sufficient to power pacemakers, hearing aids, strain sensors, communication links, and many low-power IoT objects. Such a system could potentially operate without battery, which lowers weight and prevents leakage of the energy source of a medical implant in the body.

The MIT work "is an important first demonstration of energy production from wireless ambient signals. This is all the more convincing as everything is integrated on the same flexible substrate, "says Deji Akinwande, electrical and computer engineer at the University of Texas at Austin, who was not involved in the work. "The next challenge is to scale the devices to get the higher performance needed for today's mobile applications."

Energy harvesting systems already power other remote devices to prevent frequent battery changes. Most current systems draw power from light, temperature differences, or kinetic movements, says Andreas Schneider, CEO of EnOcean, a German manufacturer of self-powered, batteryless devices that was not involved in the research. He says photovoltaic cells can provide enough light energy to provide indoor lighting with a 100 lux illuminance, which is about the same as corridor illuminance and less than one-third of office normal illuminance.

 Pressing a mechanical switch can generate enough energy to send a signal to turn on a lamp in the room or up the stairs. Temperature gradients along hot water lines can send signals to the heating system. However, the company found that the power of the ambient radio signal is insufficient for current equipment unless additional local radio transmitters have been added. Schneider says, "They do not want to sit next to one another", as they fear that electromagnetic fields could reach unhealthy levels.

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Looking ahead to the future of 5G wireless networks and the Internet of Things, Palacios says, "You might be able to use solar cells, but you only have sunlight during the day. The other possibility is to gain energy already present in radio frequency signals, "like Wi-Fi, which transmits most of the time".

Both Radio Energy Harvester and Radio Signal Receiver collect energy when radio waves interact with antennas. Electromagnetic forces reciprocate electrons in the conductive material and induce an electric current that changes in direction as the waves alternate in phase. Antennas that collect signals for radio receivers transmit the fluctuating signals to circuits that amplify and convert them into audio or video frequencies. Antennas that receive radio-frequency energy send the fluctuating power to an electronic device, a so-called rectifier, which transmits power in one direction only and converts the incoming alternating current into direct current that powers electronic devices or charges batteries.

Rectifiers are typically semiconductors, while antennas are typically metallic and highly conductive. Molybdenum disulfide is "a really good semiconductor," says Palacios. It can be modified to have high conductivity so it can serve as both an antenna and a rectifier - a device called Rectenna invented in the 1960s and now in RFID and proximity cards ( Radio Frequency Identification) is used.

Today, most rectennas are small, rigid chips of inflexible semiconductors like silicon, which have good frequency response but are limited by their inflexibility. The MIT group is the first to produce large, flexible rectennas that can extract energy from widespread, unlicensed radio frequencies of up to 10 gigahertz without the need for battery voltage to trigger the process. Flexibility and thinness are important for use in portable devices and "smart skins" that can be applied to infrastructure, aircraft, or other objects for continuous monitoring or as part of a distributed network of smart sensors. Layers as thin as three atoms can be grown on a large area at low cost by a process widely used in semiconductor fabrication - chemical vapor deposition - and still operate at very high frequencies.

The technology is still in the lab. The production has to be increased and the films have to be integrated into the devices that supply them with electricity. Another challenge will be to develop devices that can only run at ten microwatts. However, Palacios expects the first commercial applications in five to seven years. "The most important thing you need is scaling, which allows us to produce low-cost sensors over a very large area," he notes. Other applications he expects include lighting small displays by delivering 30 to 50 microwatts of power and linking implantable medical devices to external monitors. At least for a few applications, energy can really be gained from the air.

The future of electronics is light

For the last four decades, the electronics industry has been driven by the so-called "Moore's Law," which is not a law, but rather an axiom or observation. In fact, this suggests that the speed and performance of electronic devices approximately double every two years. In fact, tech companies are developing new, faster, smarter and better devices every year.

Moore's Law, as stated by Intel co-founder Gordon Moore, states that the number of transistors in a chip doubles approximately every 24 months. As they get smaller, they also become faster and consume less power for operation.

In the technology world, one of the biggest questions of the 21st century is how small can we make transistors? If there is a limit to how small they can become, we could reach a point where we can no longer make smaller, more powerful and more efficient devices. In the US alone, the industry generates more than $ 200 billion in annual revenue. Could it stop growing?

Get close to the limit

At present, companies like Intel are mass-producing 14-nanometer diameter transistors - only 14-times wider than DNA molecules. They are made of silicon, the second most abundant material on our planet. The atomic size of silicon is about 0.2 nanometers.

Today's transistors are about 70 silicon atoms wide, so that the possibility of making them even smaller, even smaller. We are approaching the limit of how small we can make a transistor.

Currently, transistors use electrical signals - electrons that move from one place to another - for communication. But if instead of electricity we could use light that consists of photons, we could make transistors even faster. My work to find ways to integrate light-based processing into existing chips is part of this new effort.

Put light in a chip

A transistor consists of three parts; Think of them as parts of a digital camera. First, information enters the lens that corresponds to the source of a transistor. Then it passes through a channel from the image sensor to the cables in the camera. Finally, the information is stored on the memory card of the camera, which is referred to as the "drain" of the transistor.

Light waves can have different frequencies. maxhurtz

At the moment, all of this happens by moving electrons around. In order to replace the medium of light, we have to move photons instead. Subatomic particles such as electrons and photons move in a wave motion and oscillate up and down, even when moving in one direction. The length of each wave depends on what it goes through.

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In silicon, the most efficient wavelength for photons is 1.3 microns. This is very small - a human hair has a diameter of about 100 microns. However, electrons in silicon are even smaller - with wavelengths that are 50 to 1000 times shorter than photons.

This means that the equipment for dealing with photons must be larger than today's devices for handling electrons. So it might seem like it would force us to build larger transistors rather than smaller ones.

However, for two reasons, we could maintain the same size of the chips and provide more processing power, shrink chips at the same power, or possibly both. First, a photonic chip requires only a few light sources, producing photons that can then be directed around the chip with very small lenses and mirrors.

And second, light is much faster than electrons. On average, photons can travel about 20 times faster than electrons in a chip. This means that computers are 20 times faster, a speed increase that would take about 15 years with the current technology.

Photonic chips

Scientists have shown progress towards photonic chips in recent years. A key challenge is to ensure that the new light-based chips are compatible with all existing electronic chips. If we can figure out how to do it, or if we even use light-based transistors to enhance electronics, we can see a significant improvement in performance.

When can I get a laptop or a smartphone with light?

We still have a long way to go before the first consumer device hits the market, and progress needs time. The first transistor was made in 1907 using vacuum tubes that were typically between one and six inches high (on average 100 mm). By 1947, the current transistor type was invented, which is now only 14 nanometers wide, and was 40 microns long (about 3,000 times longer than the current one). And in 1971, the first commercial microprocessor (the powerhouse of all electronic devices) was 1,000 times larger than it was when it first hit the market.

The enormous research effort and related development in the electronics industry is only beginning in the photonic industry. As a result, current electronics can perform tasks that are far more complex than currently best photonic devices. However, in the course of research, the power of light will reach and ultimately exceed the speed of electronics. However long it takes, the future of photonics is promising.

Paper-based electronics could fold, biodegrade and be the basis for the next generation of equipment

It seems like every few months there's a new phone, a new laptop, or a new tablet that's so exciting people are lining up to get hold of it. While the constant adoption of newer, more advanced electronics products has made companies such as Apple hugely successful, the short shelf life of these electronics products is bad for the environment.

Modern electronics

are filled with circuit boards on which different metals and plastics are soldered together. Some of these materials are toxic - or decompose into toxic substances. Efforts are being made to promote the recycling of electronic waste, to recover reusable material and to dispose of the remainder properly. However, most appliances are added to the growing pile of electronic waste in landfills.

Printed circuit boards and other electronics can be very stacked. AP Photo / Michael Conroy

Instead of adding more waste to this ever-growing pile, it is possible to develop biodegradable electronics. That's why other researchers and I are focusing on the emerging field of paper-based electronics called "papertronics." They are flexible, even foldable, sustainable, environmentally friendly and cost-effective.

To be truly environmentally friendly, Papertronik can not use conventional batteries made of metals and corrosive acids to store and discharge electricity. Recently my chemistry colleague Omowunmi Sadik and I developed a paper battery that is recyclable, biodegradable, and reliable enough to actually be used. The key is bacteria.

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Flexible bio-batteries

I have developed flexible batteries, salivary batteries, and much more. I figured it makes sense to make a battery of paper if you want paper-based electronics. Fortunately, paper is a good potential battery material: it is flexible, a good insulator - which makes it a good platform for assembling electronic components - and absorbs and releases fluids easily. We added polymers - poly (amic) acid and poly (pyromellitic dianhydride-p-phenylenediamine) - to improve these electrical properties.

To store energy in the battery, we added bacteria instead of the metals and acids that chemically react to produce electrons. When these batteries are eventually commercialized, they use bacteria that are harmless to humans and the environment and are well entrapped to reduce any other contamination.

Because the paper is rough and porous, the bacteria adhere to it and generate their own energy by decomposing almost any available organic material, including plant material or wastewater. At the moment we pack the raw material, but it could also be from the environment. This chemical reaction generates electrons. Normally, these electrons bind to oxygen in a bacterial reaction, but we've built our battery to limit oxygen and replace an electrode. This means that we can capture the electron flow and use it to power devices.

We feared that oxygen could get into the paper and disrupt the flow of electrons between the bacteria and reduce the efficiency of the battery. We have found that while this happens, it has minimal impact. This is because so many bacterial cells adhere to the paper fibers. They form a multi-layered biofilm that protects the chemical reaction from most of the oxygen.

We also wanted a battery that is biodegradable. The bacteria in the battery itself, once released, can break down the paper and polymers into harmless components. In water, our battery is easily biodegradable, with no special equipment or other microorganisms that aid in its degradation.

The polymer paper structures are lightweight, inexpensive and flexible. Thanks to this flexibility, the batteries can also be folded like a normal piece of paper or stacked on top of each other. So more battery power fits into smaller rooms.

Promises and opportunities

Papertronik can be particularly useful in remote areas with limited resources as it is powered by bacteria that live in the most extreme conditions and decompose almost any material to produce electrons. You also do not need a well-established power grid. Although paper batteries are designed to be disposed of after use, their materials are recyclable - and new batteries can be made from recycled paper.

As revolutionary as paper-based bio-batteries are for future electronic devices, they are so easy to make. The polymers and bacteria may be blended with paper or even coated or cast directly onto paper in conventional manufacturing processes, including web printing and screen printing.

The paper batteries can also be added to other materials - such as metals, semiconductors, insulators and nanoparticles. These and other substances can give paper-based devices more features and capabilities, opening new doors for the next generation of electronics.

Graphene made from DNA could change the electronics

Graphene, a single layer of carbon atoms, is touted as the material that could alter the production of electronics. However, it is difficult to produce graphene in molds needed for the electronics. Stanford University researchers have now discovered a new method of producing graphene that chemically transforms DNA matrices into shallow carbon layers, possibly overcoming this limitation.

In graphene, carbon atoms are arranged in a hexagonal structure. This symmetrical structure is a good conductor of electricity. However, shape it into bands that are narrower than 10 nanometers (one-billionth of a meter), and it can act as a semiconductor. If we can mass-produce these thin ribbons, they could be used to build very small and efficient circuits and transistors, potentially making the electronics cheaper, faster, and smaller.

Many approaches to narrow graphene tape production have been reported in recent years. These range from the uncoiling of carbon nanotubes (a form of carbon present as tiny tubes) to the burning of a graphene layer in the presence of a mask of the correct shape. Also, approaches have been described in which the graphene is prepared by chemical reactions from simple starting materials. All of these approaches have had limited success in producing long ribbons that are less than 10 nm wide

The key innovation of the Stanford team was to use DNA as a template. DNA is readily available from natural sources and can be easily manipulated into various forms, starting from the narrow bands required here for the elaboration of 3D architectures called "DNA origami". It also binds readily to metal ions such as the copper catalyst used to convert methane into graphene.

Zhenan Bao and colleagues report on these findings in the journal Nature Communications. Using a process known as molecular combing, they expanded bacterial DNA through a silicon wafer and formed the required shape. The team made both simple bands and overlapping crosses - in principle, complex circuits could be designed in this way.

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Once the DNA is present, it is soaked in a copper nitrate solution and heated to 800-1000 ° C in the presence of methane and hydrogen gases. This starts a chemical reaction that leaves a graphene-like material in the form of the DNA template. The non-carbon portions of the DNA and copper, which acts as a catalyst, evaporate in the oven to give a pure product. Most importantly, the process creates bands that are less than 10 nm wide.

There are some limitations. Graphene ribbons are not pure, crystalline graphene. About 15% of the band is made of noncrystalline carbon, which lacks the electrical properties of graphene. This reduces the ability of the ribbons to act as semiconductors; In fact, resistors are built into the bands at random locations. (To emphasize this, the authors described the bands as graphitic, which means graphene-like.)

Nevertheless, researchers were able to build transistors from the graphite tapes to demonstrate their potential applications. The presence of amorphous carbon means that high voltages must be applied to the bands before they can conduct. This shortens the life of the graphite material, and future work will certainly focus on modifying the chemistry to produce pure graphene.

The mechanism by which the bands form when heated is not yet known. Nevertheless, this work is a creative solution to an important problem. If the process can be refined to produce large amounts of pure graphene tape, the next generation of electronic devices may be one step closer.

The electronics are getting smaller and that causes big problems

Your TV, computer, smartphone, or other electronic device would not work if you were unable to conduct electrical charges across the circuits.

As these devices become more powerful, however, it becomes increasingly difficult to direct these electrical charges exactly where they are needed, as their individual components get smaller and smaller until they reach the nanoscale.

In fact, some of these nanoscale components behave very strangely, to the point where even a single atom can affect or disturb the flow of electrons. Better understanding and control of this nanoscale dynamics is therefore crucial to improving their function.

At the edge

Transistors are the building blocks of microchips and are used in computers, smartphones and amplifiers. Their function depends essentially on how electrons flow near or at the interfaces between their metallic, insulating, and semiconductor materials.

Nowadays, transistors can be up to 10 nanometers wide and get smaller and smaller. If you have a smartphone in your pocket, it probably contains more than a billion transistors.

As this miniaturization trend persists, the performance of electronic components is increasingly affected by the processes of electrons at the material boundaries because the likelihood of an electron approaching an interface increases with decreasing size.

When you are in a room, the smaller the room, the higher the probability that you are standing next to a wall.

A similar phenomenon also affects solar cells, which generate electricity when positive and negative charges are separated within a few nanometers at the boundary between electron-donating and electron-accepting materials.

Light-emitting diodes can work in reverse: they can generate light when positive and negative charges recombine at these boundaries.

Organic molecules - similar to those responsible for photosynthesis in bio-organisms - with semiconducting properties are promising materials for devices such as transistors, solar cells and light-emitting diodes.

They are inexpensive, lightweight, flexible and versatile. Their electronic properties are adjustable and their production consumes less energy than that of silicon.

To the islands

Nano-islands

Recently, we investigated two-dimensional nano-clusters - or "nano-islands" - of different size and shape composed of organic semiconducting molecules on a thin insulator to determine how the electronic properties differ at different locations on them.

We used a scanning tunneling microscope to determine the atomic structure and electronic properties of the organic nano-islands.

Measuring these currents allows us to create an image of the surface of the material to understand where atoms and electrons are located. These measurements were so sensitive that we had to perform them in a laboratory with extremely low vibration at the University of British Columbia in Canada.

Our experiments have shown that the electrons of the molecules at the edge of the nano-islands behave dramatically differently than in the middle. Importantly, these differences in electronic behavior are highly dependent on subtle variations in the position and orientation of nearby molecules.

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We found that when an electron is removed at a certain point in the center of a nano-island, the electrons of the surrounding material react and move in the direction of the positive charge generated by the removal of the electrons.

Similarly, the surrounding electrons moved away from the negative charge generated by the electron addition when an electron was added. This collective movement of electrons polarizes the environment and stabilizes the generated charge: the charge is shielded.

In contrast, the generated charge is much less efficiently shielded when an electron is removed or added at the nano-island interface - where electron transfer becomes important for technological applications.

Imagine a crowded party where someone suddenly leaves the middle of the room and creates an empty space. The people who dance around will occupy that spot much faster than if the person had left the edge of the room.

That's not surprising. What is surprising, however, is the extent of the effect. Our results show that the associated energies are very large.

Tuning in the nano range

Our work proposes a problem for the design of efficient nanoelectronic devices. Subtle features of the nanoscale structure of components not only cause severe electronic effects at their interfaces, but the influence of these effects becomes increasingly important with decreasing component size.

Therefore, it is crucial to control the arrangement of atoms and molecules at the interfaces between these components with incredible precision to develop new technologies with optimal efficiency and functionality.

Our findings open the door to new technical approaches that allow the electronic properties of nanodevices to be tuned by small and precise variations of their atomic structure.

This could be achieved by moving atoms and molecules in a controlled manner on a material surface. Another possibility is the use of supramolecular self-assembly, in which atoms and molecules interact and automatically arrange themselves in desired patterns in the nanoscale.

The effects we have discovered pose a challenge to the future of nanoelectronic devices, but also provide an excellent opportunity to develop faster and more efficient communication, information and electronic technologies.

Embroidering electronics into the next generation of "smart" fabrics

Archeology shows that about 170,000 years ago, just before the penultimate Ice Age, people wore clothing. But even today, most modern people wear clothes that are hardly different from the earliest garments. However, this will change soon as flexible electronics are increasingly being woven into so-called "smart fabrics".

Many of them are already available for purchase, such as: Gaiters that produce soft vibrations for easier yoga, T-shirts that track player performance, and sports bras that monitor heart rate. Smart substances can be promising in healthcare (measuring heart rate and blood pressure of patients), in defense (monitoring the health and activity of soldiers), in cars (adjusting seating temperatures to provide more comfort to passengers), and even in smart cities (Communication of the signs) to be used with passers-by).

Ideally, the electronic components of these garments - sensors, data transmission antennas, and power supply batteries - are small, flexible, and barely perceived by their wearers. This applies today to sensors, many of which are even machine washable. Most antennas and batteries are solid and not waterproof. They must therefore be removed from the clothing before washing.

My work at Ohio State University's ElectroScience Laboratory aims to make antennas and power sources equally flexible and washable. In particular, we embroider electronics with conductive threads, which we call "E-threads", directly in fabrics.

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Antenna embroidery

The E-threads we work with are bundles of twisted polymer filaments to ensure strength. Each thread has a metal-based coating to conduct electricity. The polymer core of each filament is typically Kevlar or Zylon while the surrounding coating is silver. Dozens or even hundreds of these filaments are then twisted into a single E-thread, usually less than half a millimeter in diameter.

These e-threads can be easily used with standard embroidery equipment - the same computer-aided sewing machines that people use to write their names on sports jackets and sweatshirts every day. The embroidered antennas are light and as good as their rigid copper counterparts and can be as complicated as state-of-the-art PCBs.

Our e-threaded antennas can even be combined with normal threads in more complex designs, such as: By integrating antennas into company logos or other designs. We were able to embroider antennas on fabrics as thin as organza and as thick as Kevlar. Once embroidered, the wires can be connected to sensors and batteries by conventional soldering or flexible interconnecting components.

So far, we've been able to create smart hats that read deep brain signals for patients with Parkinson's or epilepsy. We've embroidered T-shirts with antennas that extend the range of Wi-Fi signals to the wearer's mobile phone. We also made mats and sheets to monitor infant body size to detect a range of early childhood illnesses. And we made foldable antennas that measure how much the fabric has bent or raised on a surface.

Go beyond the antenna

My lab also collaborates with other Ohio researchers, including chemist Anne Co and physician Chandan Sen, to produce flexible, miniature fabric-based power generators.

We use a process similar to ink jet printing to place silver and zinc dots alternately on the fabric. When these metals come into contact with sweat, salt solution or even liquid escapes from wounds, silver acts as a positive electrode and zinc as a negative electrode - and electricity flows between them.

We have generated small amounts of electricity by moisturizing the fabric - without additional circuitry or components. It is a fully flexible, washable power source that can be connected to other portable electronic devices, eliminating the need for conventional batteries.

This flexible, wearable electronics transforms clothing, both together and individually, into networked, sensitive communications devices that blend well with the fabric of the connected 21st century.