Posts belonging to Category Carbon nanotubes



Light-Powered Wires To Modulate Brain’s Electrical Signals

The human brain largely remains a black box: How the network of fast-moving electrical signals turns into thought, movement and disease remains poorly understood. But it is electrical, so it can be hacked—the question is finding a precise, easy way to manipulate electrical signaling between neurons.

A new University of Chicago study shows how tiny, light-powered wires could be fashioned out of silicon to provide these electrical signals. Published Feb. 19 in Nature Nanotechnology, the study offers a new avenue to shed light on—and perhaps someday treat—brain disorders.

Ten years ago, the science world was alive with speculation about a recently discovered technique called optogenetics, which would manipulate neural activity with light. The problem is that it has to be done with genetics: inserting a gene into a target cell that would make it respond to light. Other ways of modulating neurons have since been suggested, but a perfect alternative remains elusive.

A team led by Asst. Prof. Bozhi Tian built minuscule wires previously designed for solar cells. These nanowires are so small that hundreds of them could sit side by side on the edge of a sheet of paper—putting them on the same scale as the parts of cells they’re trying to communicate with.

These nanowires combine two types of silicon to create a small electrical current when struck by light. Gold, diffused by a special process onto the surface of the wire, acts as a catalyst to promote electrochemical reactions.

The rod at top right is positioned to modify electrical signaling between the neurons. The entire image is smaller than the diameter of a single human hair.

When the wire is in place and illuminated, the voltage difference between the inside and outside of the cell is slightly reduced. This lowers the barrier for the neuron to fire an electrical signal to its neighboring cells,” Tian said.

Source: https://news.uchicago.edu/

TriboElectricity, The Green Energy Source

Researchers from Clemson’s Nanomaterials Institute (CNI) are one step closer to wirelessly powering the world using triboelectricity, a green energy source. In March 2017, a group of physicists at CNI invented the ultra-simple triboelectric nanogenerator or U-TENG, a small device made of plastic and tape that generates electricity from motion and vibrations. When the two materials are brought together — through such actions as clapping the hands or tapping feet — they generate voltage that is detected by a wired, external circuit. Electrical energy, by way of the circuit, is then stored in a capacitor or a battery until it’s needed.

Nine months later, in a paper published in the journal Advanced Energy Materials, the researchers reported that they had created a wireless TENG, called the W-TENG, which greatly expands the applications of the technology. The W-TENG was engineered under the same premise as the U-TENG using materials that are so opposite in their affinity for electrons that they generate a voltage when brought in contact with each other.

In the W-TENG, plastic was swapped for a multipart fiber made of graphene — a single layer of graphite, or pencil lead — and a biodegradable polymer known as polylactic acid (PLA). PLA on its own is great for separating positive and negative charges, but not so great at conducting electricity, which is why the researchers paired it with graphene. Kapton tape, the electron-grabbing material of the U-TENG, was replaced with Teflon, a compound known for coating nonstick cooking pans.

After assembling the graphene-PLA fiber, the researchers pulled it into a 3-D printer and the W-TENG was born. The end result is a device that generates a maximum of 3,000 volts — enough to power 25 standard electrical outlets or, on a grander scale, smart-tinted windows or a liquid crystal display (LCD) monitor. Because the voltage is so high, the W-TENG generates an electric field around itself that can be sensed wirelessly. Its electrical energy, too, can be stored wirelessly in capacitors and batteries.

It cannot only give you energy, but you can use the electric field also as an actuated remote. For example, you can tap the W-TENG and use its electric field as a ‘button’ to open your garage door, or you could activate a security system — all without a battery, passively and wirelessly,” said Sai Sunil Mallineni, the first author of the study and a Ph.D. student in physics and astronomy.

Source: http://newsstand.clemson.edu
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Hard Material With Self-Healing Capability

Imagine a cellphone that can heal from cuts and scratches just like the human body can. For Chinese researcher Ming Yang and his team at the Harbin Institute of Technology, it’s not really a question of imagining anymore: They have developed a new kind of smart coating that manages to be both soft and hard, not unlike our own skin.

We designed a self-healing coating with a hardness that even approaches tooth enamel by mimicking the structure of epidermis,” Yang says. “This is the most desirable property combination in the current self-healing materials and coatings.”

As described in a paper published Wednesday in ACS Nano, this new material is far from the first smart coating, with previous research looking at both soft and hard coating options. Yang says there’s serious global need for better self-healing materials.

Nowadays people always talk about environment and energy,” he adds. “A self-healing material can help save a lot of money and energy using a smart, environmental friendly way. But the current self-healing materials and coatings are typically soft and wear out quickly. This can bring potential problems about the management of plastic waste.

This new material could solve those waste problems, as it comes closer than any predecessor to combining the flexibility of a soft coating and the resilience of a hard coating, without the short lifespan of the former or the brittleness of the latter. This could be the best of both worlds.

The trick is to use artificial materials in nature’s way,” explains Yang. “The multilayer structure is the key. By placing a hard layer containing graphene oxide on top of a soft layer, we create a smart hybridization you can get the most out of.”

The graphene oxide material used in the coating’s top layer is harder than skin cells, offering a toughness closer to that of teeth enamel. The amazing thing, according to Yang, is that the coating’s hard and soft layers are able to work together to create healing properties that neither could accomplish on its own.

Source: https://pubs.acs.org/
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Hydrogen Economy Closer

Washington State University (WSU) researchers have found a way to more efficiently generate hydrogen from water — an important key to making clean energy more viable. Using inexpensive nickel and iron, the researchers developed a very simple, five-minute method to create large amounts of a high-quality catalyst required for the chemical reaction to split water.

Energy conversion and storage is a key to the clean energy economy. Because solar and wind sources produce power only intermittently, there is a critical need for ways to store and save the electricity they create. One of the most promising ideas for storing renewable energy is to use the excess electricity generated from renewables to split water into oxygen and hydrogen. Hydrogen has myriad uses in industry and could be used to power hydrogen fuel-cell carsIndustries have not widely used the water splitting process, however, because of the prohibitive cost of the precious metal catalysts that are required – usually platinum or ruthenium. Many of the methods to split water also require too much energy, or the required catalyst materials break down too quickly.

In their work, the researchers, led by professor Yuehe Lin in the School of Mechanical and Materials Engineering, used two abundantly available and cheap metals to create a porous nanofoam that worked better than most catalysts that currently are used, including those made from the precious metals. The catalyst they created looks like a tiny sponge. With its unique atomic structure and many exposed surfaces throughout the material, the nanofoam can catalyze the important reaction with less energy than other catalysts. The catalyst showed very little loss in activity in a 12-hour stability test.

We took a very simple approach that could be used easily in large-scale production,” said Shaofang Fu, a WSU Ph.D. student who synthesized the catalyst and did most of the activity testing. “The advanced materials characterization facility at the national laboratories provided the deep understanding of the composition and structures of the catalysts,” comments Junhua Song, another WSU Ph.D. student who worked on the catalyst characterization.

The findings are described in the journal Nano Energy.

Source: https://news.wsu.edu/

Flexible, Low-Cost, Water-Repellent Gaphene Circuits

New graphene printing technology can produce electronic circuits that are low-cost, flexible, highly conductive and water repellent. The nanotechnology “would lend enormous value to self-cleaning wearable/washable electronics that are resistant to stains, or ice and biofilm formation,” according to a recent paper describing the discovery.

“We’re taking low-cost, inkjet-printed graphene and tuning it with a laser to make functional materials,” said Jonathan Claussen, an Iowa State University assistant professor of mechanical engineering, an associate of the U.S. Department of Energy’s and the corresponding author of the paper recently featured on the cover of the journal Nanoscale. The paper describes how Claussen and the nanoengineers in his research group use to create electric circuits on flexible materials. In this case, the ink is flakes of graphene – the wonder material can be a great conductor of electricity and heat, plus it’s strong, stable and biocompatible.

And now they’ve found another application of their laser processing technology: taking graphene-printed circuits that can hold water droplets (they’re hydrophilic) and turning them into circuits that repel water (they’re superhydrophobic).

We’re micro-patterning the surface of the inkjet-printed graphene,” Claussen said. “The laser aligns the graphene flakes vertically – like little pyramids stacking up. And that’s what induces the hydrophobicity.” Claussen said the energy density of the laser processing can be adjusted to tune the degree of hydrophobicity and conductivity of the printed graphene circuits. And that opens up all kinds of possibilities for new electronics and sensors, according to the paper. “One of the things we’d be interested in developing is anti-biofouling materials,” said Loreen Stromberg, a paper co-author and an Iowa State postdoctoral research associate in mechanical engineering and for the Virtual Reality Applications Center. “This could eliminate the buildup of biological materials on the surface that would inhibit the optimal performance of devices such as chemical or biological sensors.”

The technology could also have applications in flexible electronics, washable sensors in textiles, microfluidic technologies, drag reduction, de-icing, electrochemical sensors and technology that uses graphene structures and electrical simulation to produce stem cells for nerve regeneration. The researchers wrote that further studies should be done to better understand how the nano– and microsurfaces of the printed graphene creates the water-repelling capabilities. .

The Iowa State University Research Foundation is working to patent the technology and has optioned it to an Ames-based startup, NanoSpy Inc., for possible commercialization. NanoSpy, located at the Iowa State University Research Park, is developing sensors to detect salmonella and other pathogens in food processing plants. Claussen and Stromberg are part of the company.

Source: https://www.news.iastate.edu/

Universal Vaccine Against Influenza A Viruses

Researchers have developed a universal vaccine to combat influenza A viruses that produces long-lasting immunity in mice and protects them against the limitations of seasonal flu vaccines, according to a study led by Georgia State UniversityInfluenza, a contagious respiratory illness that infects the nose, throat and lungs, is among the leading causes of death in the United States, according to the Centers for Disease Control and Prevention (CDC). The CDC estimates influenza has resulted in between 12,000 and 56,000 deaths annually in the U.S. since 2010. Seasonal flu vaccines must be updated each year to match the influenza viruses that are predicted to be most common during the upcoming flu season, but protection doesn’t always meet expectations or new viruses emerge and manufacturers incorrectly guess which viruses will end up spreading. In 2009, the H1N1 pandemic caused 200,000 deaths during the first 12 months, and low vaccine effectiveness was also observed during the 2014-15 and 2016-17 flu seasons. A universal flu vaccine that offers broad protection against various viruses is urgently needed and would eliminate the limitations of seasonal flu vaccines.

Seasonal flu vaccines provide protective immunity against influenza viruses by targeting the exterior head of the virus’s surface protein, which is hem
agglutinin
(HA). The influenza virus trains the body to produce antibodies against inactivated virus particles containing the head of this protein, ideally preventing the head from attaching to receptors and stopping infection. However, the head is highly variable and is different for each virus, creating a need for better vaccines. This study uses a new approach and instead targets the inside portion of the HA protein known as the stalk, which is more conservative and offers the opportunity for universal protection.

In this study, the researchers found vaccinating mice with double-layered protein nanoparticles that target the stalk of this protein produces long-lasting immunity and fully protects them against various influenza A viruses. The findings are published in the journal Nature Communications.

Source: http://news.gsu.edu/

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.

Source: http://news.mit.edu/

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.

Source: https://warwick.ac.uk/

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

Source: https://ucrtoday.ucr.edu/

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.

Source: http://resou.osaka-u.ac.jp/

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.

Source: https://sciencebusiness.net/

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.

Source: https://news.ucsc.edu/