Posts belonging to Category Graphene

Artificial Synapse For “Brain-on-a-Chip”

When it comes to processing power, the human brain just can’t be beat. Packed within the squishy, football-sized organ are somewhere around 100 billion neurons. At any given moment, a single neuron can relay instructions to thousands of other neurons via synapses — the spaces between neurons, across which neurotransmitters are exchanged. There are more than 100 trillion synapses that mediate neuron signaling in the brain, strengthening some connections while pruning others, in a process that enables the brain to recognize patterns, remember facts, and carry out other learning tasks, at lightning speeds.

Researchers in the emerging field of “neuromorphic computing” have attempted to design computer chips that work like the human brain. Instead of carrying out computations based on binary, on/off signaling, like digital chips do today, the elements of a “brain on a chip” would work in an analog fashion, exchanging a gradient of signals, or “weights,” much like neurons that activate in various ways depending on the type and number of ions that flow across a synapse.

In this way, small neuromorphic chips could, like the brain, efficiently process millions of streams of parallel computations that are currently only possible with large banks of supercomputers. But one significant hangup on the way to such portable artificial intelligence has been the neural synapse, which has been particularly tricky to reproduce in hardware.

Now engineers at MIT have designed an artificial synapse in such a way that they can precisely control the strength of an electric current flowing across it, similar to the way ions flow between neurons. The team has built a small chip with artificial synapses, made from silicon germanium. In simulations, the researchers found that the chip and its synapses could be used to recognize samples of handwriting, with 95 percent accuracy.

The design, published today in the journal Nature Materials, is a major step toward building portable, low-power neuromorphic chips for use in pattern recognition and other learning tasks.


Adding Graphene To Silicon Electrodes Double Lithium Batteries Life

New research led by WMG (academic department), at the University of Warwick (UK) has found an effective approach to replacing graphite in the anodes of lithium-ion batteries using silicon, by reinforcing the anode’s structure with graphene girders. This could more than double the life of rechargeable lithium-ion based batteries by greatly extending the operating lifetime of the electrode, and also increase the capacity delivered by those batteries.

Graphite has been the default choice of active material for anodes in lithium—ion batteries since their original launch by Sony but researchers and manufacturers have long sought a way to replace graphite with silicon, as it is an abundantly available element with ten times the gravimetric energy density of graphite. Unfortunately, silicon has several other performance issues that continue to limit its commercial exploitation.

Due to its volume expansion upon lithiation silicon particles can electrochemically agglomerate in ways that impede further charge-discharge efficiency over time. Silicon is also not intrinsically elastic enough to cope with the strain of lithiation when it is repeatedly charged, leading to cracking, pulverisation and rapid physical degradation of the anode’s composite microstructure. This contributes significantly to capacity fade, along with degradation events that occur on the counter electrode – the cathode. To use the mobile phones as an example, this is why we have to charge our phones for a longer and longer time, and it is also why they don’t hold their charge for as long as when they are new.

However new research, led by Dr Melanie Loveridge in WMG at the University of Warwick, has discovered, and tested, a new anode mixture of silicon and a form of chemically modified graphene which could resolve these issues and create viable silicon anode lithium-ion batteries. Such an approach could be practically manufactured on an industrial scale and without the need to resort to nano sizing of silicon and its associated problems.

The new research has been published in Nature Scientific Reports.


Making Fuel Cells for a Fraction of the Cost

It is the third announcement in less than one week for a major improvment in the making of fuel cells.

In the competition between Lithium-Ion batteries (e.g. Tesla cars), and hydrogen fuel cells (see picture of Nexo from Hyundai) that power electric cars, it is difficult to predict which one will be the winner at the end.

Fuel cells have the potential to be a clean and efficient way to run cars, computers, and power stations, but the cost of producing them is limiting their use. That’s because a key component of the most common fuel cells is a catalyst made from the precious metal platinum.

In a paper published in Small, researchers at the University of California, Riverside (UCR), describe the development of an inexpensive, efficient catalyst material for a type of fuel cell called a polymer electrolyte membrane fuel cell (PEMFC), which turns the chemical energy of hydrogen into electricity and is among the most promising fuel cell types to power cars and electronics.

The catalyst developed at UCR is made of porous carbon nanofibers embedded with a compound made from a relatively abundant metal such as cobalt, which is more than 100 times less expensive than platinum. The research was led by David Kisailus, the Winston Chung Endowed Professor in Energy Innovation in UCR’s Marlan and Rosemary Bourns College of Engineering.

Fuel cells, which are already being used by some carmakers, offer advantages over conventional combustion technologies, including higher efficiency, quieter operation and lower emissions. Hydrogen fuel cells emit only water.

Like batteries, fuel cells are electrochemical devices that comprise a positive and negative electrode sandwiching an electrolyte. When a hydrogen fuel is injected onto the anode, a catalyst separates the hydrogen molecules into positively charged particles called protons and negatively charged particles called electrons. The electrons are directed through an external circuit, where they do useful work, such as powering an electric motor, before rejoining the positively charged hydrogen ions and oxygen to form water.

A critical barrier to fuel cell adoption is the cost of platinum, making the development of alternative catalyst materials a key driver for their mass implementation.

Using a technique called electrospinning, the UCR researchers made paper-thin sheets of carbon nanofibers that contained metal ions — either cobalt, iron or nickel. Kisailus and his team, collaborating with scientists at Stanford University, determined that the new materials performed as good as the industry standard platinum-carbon systems, but at a fraction of the cost. “The key to the high performance of the materials we created is the combination of the chemistry and fiber processing conditions,” Kisailus said


Solar-driven Hydrogen Economy

Hydrogen as a fuel source, rather than hydrocarbons like oil and coal, offers many benefits. Burning hydrogen produces harmless water with the potential to eliminate carbon dioxide emissions and their environmental burden. In pursuit of technologies that could lead to a breakthrough in achieving a hydrogen economy, a key issue is making hydrogen cheaply. Using catalysts to split water is the ideal way to generate hydrogen, but doing so usually requires an energy input from other chemicals, electricity, or a portion of sunlight which has high enough energy.

Now researchers at Osaka University have developed a new catalytic system for efficiently splitting water and making hydrogen with energy from normal sunlight. Their study was recently reported in Angewandte Chemie International Edition.

It has not been possible to use visible light for photocatalysis, but our approach of combining nanostructured black phosphorus for water reduction to hydrogen and bismuth vanadate for water oxidation to oxygen lets us make use of a wide range of the solar spectrum to make hydrogen and oxygen with unprecedented efficiency,” lead author Mingshan Zhu says.

Black phosphorus has a flat, two-dimensional structure similar to that of graphene and strongly absorbs light across the whole of the visible spectrum. The researchers combined the black phosphorus with bismuth vanadate, which is a well-known water oxidation catalyst.

In the same way that plants shuttle electrons between different structures in natural photosynthesis to split water and make oxygen, the two components of this new catalyst could rapidly transfer electrons excited by sunlight. The amounts of the two components was also optimized in the catalyst, leading to production of hydrogen and oxygen gases in an ideal 2:1 ratio.


Europe: 17 Organizations United To Produce Li-Ion Batteries

Energy storage has emerged as a central building block of the EU’s objectives in low emission electric transport and replacing electricity generated by fossil fuels with renewables. The realisation that batteries are of such strategic importance has come as a wake-up call, with Europe finding itself lagging in commercialising research in the field, and for now, completely dependent on manufacturers outside the EU for battery supplies. Public and private funders in Europe that have put €555 million into developing new energy storage technologies since 2008 have little to show for it in terms of commercial outputs.

While a number of start-ups, such as France’s NAWA Technology are working on various approaches to increasing energy density and speeding up recharging of electric vehicle batteries, none are in production. As yet, Europe has no factories producing electric vehicle batteries, though LG Chem of South Korea is currently constructing a manufacturing plant in Poland, which is due to open later this year. Another Korean manufacturer, SK Innovation, whose major customer is Mercedes-Benz, has announced it will invest $777 million to build a battery plant with capacity of 7.5 GW/year in Hungary

A European company, Northvolt is planning to build a plant in Skelleftea, northern Sweden, with construction due to start in the second half of 2018. Meanwhile, Frankfurt-based TerraE announced earlier in January that it has formed a consortium of 17 companies and research institutions to handle the planning for two large-scale lithium-ion battery cell manufacturing facilities in Germany. TerraE will build and operate the factories, where customers can have batteries produced to their own specifications.


Ultra-Thin Memory Storage For Nanocomputer

Engineers worldwide have been developing alternative ways to provide greater memory storage capacity on even smaller computer chips. Previous research into two-dimensional atomic sheets for memory storage has failed to uncover their potential — until now. A team of electrical engineers at The University of Texas at Austin, in collaboration with Peking University scientists, has developed the thinnest memory storage device with dense memory capacity, paving the way for faster, smaller and smarter computer chips for everything from consumer electronics to big data to brain-inspired computing.

For a long time, the consensus was that it wasn’t possible to make memory devices from materials that were only one atomic layer thick,” said Deji Akinwande, associate professor in the Cockrell School of Engineering’s Department of Electrical and Computer Engineering. “With our new ‘atomristors,’ we have shown it is indeed possible.”

Made from 2-D nanomaterials, the “atomristors” — a term Akinwande coined — improve upon memristors, an emerging memory storage technology with lower memory scalability. He and his team published their findings in the January issue of Nano Letters.

Atomristors will allow for the advancement of Moore’s Law at the system level by enabling the 3-D integration of nanoscale memory with nanoscale transistors on the same chip for advanced computing systems,” Akinwande said.

Memory storage and transistors have, to date, always been separate components on a microchip, but atomristors combine both functions on a single, more efficient computer system. By using metallic atomic sheets (graphene) as electrodes and semiconducting atomic sheets (molybdenum sulfide) as the active layer, the entire memory cell is a sandwich about 1.5 nanometers thick, which makes it possible to densely pack atomristors layer by layer in a plane. This is a substantial advantage over conventional flash memory, which occupies far larger space. In addition, the thinness allows for faster and more efficient electric current flow.

Given their size, capacity and integration flexibility, atomristors can be packed together to make advanced 3-D chips that are crucial to the successful development of brain-inspired computing. One of the greatest challenges in this burgeoning field of engineering is how to make a memory architecture with 3-D connections akin to those found in the human brain.

The sheer density of memory storage that can be made possible by layering these synthetic atomic sheets onto each other, coupled with integrated transistor design, means we can potentially make computers that learn and remember the same way our brains do,” Akinwande said.


Efficient, Low-Cost Catalyst To Produce Hydrogen

A nanostructured composite material developed at UC Santa Cruz has shown impressive performance as a catalyst for the electrochemical splitting of water to produce hydrogen. An efficient, low-cost catalyst is essential for realizing the promise of hydrogen as a clean, environmentally friendly fuel.

Researchers led by Shaowei Chen, professor of chemistry and biochemistry at UC Santa Cruz, have been investigating the use of carbon-based nanostructured materials as catalysts for the reaction that generates hydrogen from water. In one recent study, they obtained good results by incorporating ruthenium ions into a sheet-like nanostructure composed of carbon nitride. Performance was further improved by combining the ruthenium-doped carbon nitride with graphene, a sheet-like form of carbon, to form a layered composite.

The bonding chemistry of ruthenium with nitrogen in these nanostructured materials plays a key role in the high catalytic performance,” Chen said. “We also showed that the stability of the catalyst is very good.”

Currently, the most efficient catalysts for the electrochemical reaction that generates hydrogen from water are based on platinum, which is scarce and expensive. Carbon-based materials have shown promise, but their performance has not come close to that of platinum-based catalysts.

In the new composite material developed by Chen’s lab, the ruthenium ions embedded in the carbon nitride nanosheets change the distribution of electrons in the matrix, creating more active sites for the binding of protons to generate hydrogen. Adding graphene to the structure further enhances the redistribution of electrons.

The new findings were published in ChemSusChem.


Memristors Retain Data 10 Years Without Power

The internet of things ( IoT) is coming, that much we know. But still it won’t; not until we have components and chips that can handle the explosion of data that comes with IoT. In 2020, there will already be 50 billion industrial internet sensors in place all around us. A single autonomous device – a smart watch, a cleaning robot, or a driverless car – can produce gigabytes of data each day, whereas an airbus may have over 10 000 sensors in one wing alone.

Two hurdles need to be overcome. First, current transistors in computer chips must be miniaturized to the size of only few nanometres; the problem is they won’t work anymore then. Second, analysing and storing unprecedented amounts of data will require equally huge amounts of energy. Sayani Majumdar, Academy Fellow at Aalto University (Finland), along with her colleagues, is designing technology to tackle both issues.

Majumdar has with her colleagues designed and fabricated the basic building blocks of future components in what are called “neuromorphiccomputers inspired by the human brain. It’s a field of research on which the largest ICT companies in the world and also the EU are investing heavily. Still, no one has yet come up with a nano-scale hardware architecture that could be scaled to industrial manufacture and use.

The probe-station device (the full instrument, left, and a closer view of the device connection, right) which measures the electrical responses of the basic components for computers mimicking the human brain. The tunnel junctions are on a thin film on the substrate plate.

The technology and design of neuromorphic computing is advancing more rapidly than its rival revolution, quantum computing. There is already wide speculation both in academia and company R&D about ways to inscribe heavy computing capabilities in the hardware of smart phones, tablets and laptops. The key is to achieve the extreme energy-efficiency of a biological brain and mimic the way neural networks process information through electric impulses,” explains Majumdar.

In their recent article in Advanced Functional Materials, Majumdar and her team show how they have fabricated a new breed of “ferroelectric tunnel junctions”, that is, few-nanometre-thick ferroelectric thin films sandwiched between two electrodes. They have abilities beyond existing technologies and bode well for energy-efficient and stable neuromorphic computing.

The junctions work in low voltages of less than five volts and with a variety of electrode materials – including silicon used in chips in most of our electronics. They also can retain data for more than 10 years without power and be manufactured in normal conditions.

Tunnel junctions have up to this point mostly been made of metal oxides and require 700 degree Celsius temperatures and high vacuums to manufacture. Ferroelectric materials also contain lead which makes them – and all our computers – a serious environmental hazard.

Our junctions are made out of organic hydro-carbon materials and they would reduce the amount of toxic heavy metal waste in electronics. We can also make thousands of junctions a day in room temperature without them suffering from the water or oxygen in the air”, explains Majumdar.

What makes ferroelectric thin film components great for neuromorphic computers is their ability to switch between not only binary states – 0 and 1 – but a large number of intermediate states as well. This allows them to ‘memoriseinformation not unlike the brain: to store it for a long time with minute amounts of energy and to retain the information they have once received – even after being switched off and on again.

We are no longer talking of transistors, but ‘memristors’. They are ideal for computation similar to that in biological brains.  Take for example the Mars 2020 Rover about to go chart the composition of another planet. For the Rover to work and process data on its own using only a single solar panel as an energy source, the unsupervised algorithms in it will need to use an artificial brain in the hardware.

What we are striving for now, is to integrate millions of our tunnel junction memristors into a network on a one square centimetre area. We can expect to pack so many in such a small space because we have now achieved a record-high difference in the current between on and off-states in the junctions and that provides functional stability. The memristors could then perform complex tasks like image and pattern recognition and make decisions autonomously,” says Majumdar.


Flat Lens Boost Virtual Reality

Metalensesflat surfaces that use nanostructures to focus light — promise to revolutionize optics by replacing the bulky, curved lenses currently used in optical devices with a simple, flat surface.  But, these metalenses have remained limited in the spectrum of light they can focus well Now a team of researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) has developed the first single lens that can focus the entire visible spectrum of light — including white light — in the same spot and in high resolution. This has only ever been achieved in conventional lenses by stacking multiple lenses.

Focusing the entire visible spectrum and white light – combination of all the colors of the spectrum — is so challenging because each wavelength moves through materials at different speeds. Red wavelengths, for example, will move through glass faster than the blue, so the two colors will reach the same location at different times resulting in different foci. This creates image distortions known as chromatic aberrations.

Cameras and optical instruments use multiple curved lenses of different thicknesses and materials to correct these aberrations, which, of course, adds to the bulk of the device.

Metalenses have advantages over traditional lenses,” says Federico Capasso, Professor of Applied Physics at SEAS and senior author of the research. “Metalenses are thin, easy to fabricate and cost effective. This breakthrough extends those advantages across the whole visible range of light. This is the next big step. Using our achromatic lens, we are able to perform high quality, white light imaging. This brings us one step closer to the goal of incorporating them into common optical devices such as cameras“.

The research is published in Nature Nanotechnology.


Nano-based Chip Detects Explosives

Technical University of Denmark (DTU) is ready with a prototype for a chemical “sniffer system” for the detection of criminal substances like narcotics and explosivesDogs have an eminent sense of smell. Their snouts use a specific sniffing technique which almost grabs hold of scents. Elephants’ snouts are even better than those of dogs, but obviously these are attached to elephants which are difficult to carry around. Consequently, today dogs are employed to track narcotics, money and explosives. Sometimes dogs are able to sense explosives in very small doses, however, they are not always 100 percent reliable as they are also sensitive to changes in their surroundings. A technological solution is therefore to be preferred in the tracking of stocks of narcotics or explosive materials.

Researchers at DTU have developed the prototype of a chip able to sniff molecular structures from a number of known substances. A special camera visualises the results from the chip (with 24 megapixels per 15 second) and newly developed software interprets these images according to changes in colour (i.e. the difference between two pictures), caused by the impact of the scents in the air.

We have conducted experiments by sucking air from smaller containers like e.g. handbags or pieces of luggage and from large industrial sized containers typically used for smuggling. In both cases, we arrived at promising results”, says Mogens Havsteen Jakobsen, Senior Researcher at DTU Nanotech.

By using the so-called colorimetric sensing technique, the artificial nose is able to detect different substances like explosives, narcotics, the ripeness of cheese, rotten meat and fish, the quality of wine and coffee or bad indoor climate of a room.

The project has specifically targeted explosives which are a growing safety risk in our society. The Chemical Division of the Danish Emergency Management Agency has been an important collaborator because they are authorised to produce and handle explosives. “We have test laboratories which have been made available during the course of the project”, says Jesper Mogensen, civil engineer and analysis chemist at the Chemical Division and therefore used to handling explosives.

There will be some evident advantages in using a technology such as CRIM-TRACK, compared to the instruments available today,” Jesper Mogensen says. “Firstly, the preparation time is short in that what you largely need to do is switch on the tracker and use it. This is valuable time saved. Secondly and perhaps the most important advantage is the fact that the EOD (the Explosive Ordnance Disposal) does not need to collect a sample. Today when we are called to a ransacking if e.g. a kilo of white powder has been found and we have to analyse its chemistry by way of GC-MS (i.e. gas chromatography-mass spectrometry), a sample of the substance must be collected on a fibre. In other words, it is necessary to collect physically a sample with all the risks this entails. With DTU’s sniffer system, it is possible to collect samples in the air. It sniffs for the drug much like a dog and indicates whether there are any explosives or not. This will increase the safety of our EOD”.


In 2025 Humanity Could Benefit From A Major New Source Of Clean Power

An international project to generate energy from nuclear fusion has reached a key milestone, with half of the infrastructure required now built. Bernard Bigot, the director-general of the International Thermonuclear Experimental Reactor (Iter), the main facility of which is based in southern France, said the completion of half of the project meant the effort was back on track, after a series of difficulties. This would mean that power could be produced from the experimental site from 2025.

Nuclear fusion occurs when two atoms combine to form a new atom and a neutron. The atoms are fired into a plasma where extreme temperatures overcome their repulsion and forces them together. The fusion releases about four times the energy produced when an atom is split in conventional nuclear fission

The effort to bring nuclear fusion power closer to operation is backed by some of the world’s biggest developed and emerging economies, including the EU, the US, China, India, Japan, Korea and Russia. However, a review of the long-running project in 2013 found problems with its running and organisation. This led to the appointment of Bigot, and a reorganisation that subsequent reviews have broadly endorsed.

Fusion power is one of the most sought-after technological goals in the pursuit of clean energy. Nuclear fusion is the natural phenomenon that powers the sun, converting hydrogen into helium atoms through a process that occurs at extreme temperatures.

Replicating that process on earth at sufficient scale could unleash more energy than is likely to be needed by humanity, but the problem is creating the extreme conditions necessary for such reactions to occur, harnessing the resulting energy in a useful way, and controlling the reactions once they have been induced.

The Iter project aims to use hydrogen fusion, controlled by large superconducting magnets, to produce massive heat energy which would drive turbines – in a similar way to the coal-fired and gas-fired power stations of today – that would produce electricity. This would produce power free from carbon emissions, and potentially at low cost, if the technology can be made to work at a large scale.

For instance, according to Iter scientists, an amount of hydrogen the size of a pineapple could be used to produce as much energy as 10,000 tonnes of coal.


Nano-based Air Purifier Destroys Pollutants

Molekule, a San Francisco-based startup with a sleekly designed molecular air purifier started as an immigrant dream twenty years ago and ended up being named one of Time’s top 25 inventions of 2017. The inventor Yogi Goswami came up with the idea when his baby son Dilip started having a hard time breathing the air around him. Dilip suffered from severe asthma but no air purifier at the time seemed to work well enough to clean up indoor pollutants. Traditional HEPA filters simply trap a few pollutants but they don’t grab everything and they don’t break them down before releasing them back into the air.

So, Goswami the elder came up with a filter technology that could both suck up things like allergens, mold and bacteria and particles up to one-thousand times smaller than what a HEPA filter can catch using photo electrochemical oxidation (PECO) and nanotechnology to destroy the pollutants on a molecular level and eliminate the full spectrum of indoor air pollutants. The result? Clean, breathable air that even the most sensitive person can handle. Dilip and his sister Jaya Goswami patented the tech and founded Molekule to bring their father’s invention to the rest of us.

The company now ships a stylish $800, two-foot-tall cylinder with the patented filter inside. Sure, it’s a lot pricier than most filters out there but the company also offers financing at $67 a month. It was also instrumental in helping folks breathe during the Northern California wildfires this fall. Jaya mentioned Molekule’s inventory was completely depleted during that time and that the company couldn’t ship fast enough — the product is still backordered till January 3rd, 2018. So far Molekule has brought in just over $13 million in venture funding to keep it going.