Scientists and engineers at the U.S. Army Research Laboratory (ARL) in Maryland have demonstrated a new nanomaterial powder that creates large amounts of energy by simply mixing it with water.
Credit: U.S. Army Research Laboratory
The substance is described as a nano-galvanic aluminium-based powder. It creates a bubbling reaction that splits apart water – two molecules of hydrogen and one of oxygen.
"The hydrogen that is given off can be used as a fuel in a fuel cell," said Scott Grendahl, a materials engineer and team leader. "What we discovered is a mechanism for a rapid and spontaneous hydrolysis of water."
It has already been known for a long time that hydrogen can be produced by adding a catalyst to aluminium. However, this normally takes time and requires elevated temperatures, added electricity and/or toxic chemicals. By contrast, the nanomaterial powder seen here does not require a catalyst and is very fast. The team calculates that one kilogram of the powder can produce 220 kilowatts of energy in just three minutes, which is doubled if you consider the amount of heat energy produced by the exothermic reaction.
"That's a lot of power to run any electrical equipment," said Dr. Anit Giri, a physicist for the Weapons and Materials Research Directorate. "These rates are the fastest known without using catalysts such as an acid, base or elevated temperatures."
As seen in the video, the team demonstrated a small radio-controlled tank powered by the powder and water reaction. They believe their discovery is dramatic in terms of future potential. It could be 3-D printed and incorporated into future air or ground robots. These self-cannibalising machines would feed off their own structures, then self-destruct after mission completion. It could also help future soldiers to recharge mobile devices for recon teams.
"There are other researchers who have been searching their whole lives and their optimised product takes many hours to achieve, say 50% efficiency," Grendahl said. "Ours does it to 100% efficiency in less than three minutes."
"The important aspect of the approach is that it lets you make very compact systems," notes Anthony Kucernak from Imperial College London, who was not involved in this particular study, but is an expert on fuel cell technology. "That would be very useful for systems which need to be very light or operate for long periods on hydrogen, where the use of hydrogen stored in a cylinder is prohibitive."
Researchers in the U.S. have created "smart windows" that rapidly change opacity, depending on how sunny it is. This new technology could cut utility costs.
Engineers at Stanford University have created dynamically changing windows that can switch from transparent to opaque in only a minute – and back again in just 20 seconds – a major improvement over dimming windows currently being installed to reduce cooling costs in some buildings.
The newly designed "smart" windows consist of conductive glass plates outlined with metal ions that spread out over the surface, blocking light in response to an electrical current. The results are described in the 9th August edition of the journal Joule.
"We're excited because dynamic window technology has the potential to optimise the lighting in rooms or vehicles, and save about 20 percent in heating and cooling costs," said Michael McGehee, a professor of materials science and engineering at Stanford and senior author of the study. "It could even change the way people wear sunglasses."
Credit: Barile et al./Joule 2017
The researchers have filed a patent for their new technology and have entered into discussions with glass manufacturers and other potential partners. However, more research is needed to make the surface area of the windows large enough for commercial applications. The prototypes used in the study are only about 4 square inches (25 square centimetres) in size. The team also wants to reduce manufacturing costs to be competitive with dynamic windows already on the market.
"This is an important area that is barely being investigated at universities," McGehee said. "There's a lot of opportunity to keep us motivated."
Commercially available smart windows are made of materials, such as tungsten oxide, that change colour when charged with electricity. But these tend to be expensive, have a blue tint, can take more than 20 minutes to dim, and become less opaque over their lifetime. The Stanford prototype blocks light through the movement of a copper solution over a sheet of indium tin oxide, modified with platinum nanoparticles.
Credit: Barile et al./Joule 2017
When transparent, the window is clear and lets roughly 80 percent of incoming natural light pass through. When dark, the transmission of light drops below five percent. To test its durability, the researchers switched the windows on and off more than 5,000 times and saw no degradation in the transmission of light.
"We've had a lot of moments where we thought, how is it even possible we've made something that works so well so quickly?" McGehee said. "We didn't tweak what was out there. We came up with a completely different solution."
Perhaps in some future decade, with further advances in nanotechnology, smart windows could be developed that respond to sunlight in real time and instantly change colour – while being affordable enough to feature as standard in every building and vehicle.
Researchers at the University of Tokyo have made a "breathable" nanoscale mesh with an electronic sensor that can be worn on the skin for a week without discomfort, and could potentially monitor a person's health continuously for long periods.
Credit: 2017 Someya Laboratory
A hypoallergenic, electronic sensor can be worn on the skin continuously for a week without discomfort, and is so light and thin that users forget they even have it on, says a group of Japanese scientists. The elastic electrode, constructed of "breathable" nanoscale meshes, holds promise for the development of non-invasive e-skin devices that can monitor a person's health continuously over a long period.
Wearable electronics that monitor heart rate and other health signs have made headway in recent years, with next-generation gadgets employing lightweight, elastic materials attached directly to the skin for more sensitive, precise measurements. However, while the ultrathin films and rubber sheets in these devices adhere and conform well to the skin, their lack of breathability is deemed unsafe for long-term use: dermatological tests show the fine, stretchable materials prevent sweating and block airflow around the skin, causing irritation and inflammation, which could lead to lasting physiological and psychological effects.
"We learned that devices that can be worn for a week or longer for continuous monitoring were needed for practical use in medical and sports applications," says Professor Takao Someya at the University of Tokyo's Graduate School of Engineering. His research group has previously developed an on-skin patch for measuring oxygen in blood.
In their latest research, they developed an electrode constructed from nanoscale meshes containing a water-soluble polymer, polyvinyl alcohol (PVA), and a gold layer – materials considered safe and biologically compatible with the body. The device can be applied by spraying a tiny amount of water, which dissolves the PVA nanofibres and allows it to stick easily to the skin – it will conform seamlessly with curvilinear surfaces of human skin, such as sweat pores and the ridges of fingerprint patterns.
Credit: 2017 Someya Laboratory
The researchers conducted a skin patch test on 20 subjects and detected no inflammation of skin after they had worn the device for a week. The group also evaluated the permeability, with water vapour, of the nanomesh conductor – along with those of other substrates like ultrathin plastic foil and a rubber sheet – and found that its porous mesh structure exhibited superior gas permeability compared to other materials.
Furthermore, the scientists proved the device's mechanical durability through repeated bending and stretching, exceeding 10,000 times, of a conductor attached on the forefinger; they also established its reliability as an electrode for electromyogram recordings when its readings of the electrical activity of muscles were comparable to those obtained through conventional gel electrodes.
"It will become possible to monitor patients' vital signs without causing any stress or discomfort," says Someya about the future applications. In addition to nursing care and medical uses, the new device could enable continuous, precise monitoring of athletes' physiological signals and bodily motion without impeding their training or performance. The team's research is published this week in Nature Nanotechnology.
An array of nanomesh conductors attached to a fingertip, top, and a scanning electron microscope (SEM) image
of a nanomesh conductor on a skin replica, bottom. Credit: 2017 Someya Laboratory.
Traditional silicon-based transistors revolutionised electronics with their ability to switch current on and off. By controlling the flow of current, the creation of smaller computers and other devices was possible. Over the decades, rapid gains in miniaturisation led to computers shrinking from room-sized monoliths, to wardrobe-sized, to desktops and laptops and eventually handheld smartphones – a phenomenon known as Moore's Law. In recent years, however, concerns have arisen that the rate of progress may have slowed, or could even be approaching a fundamental limit.
A solution may be on the horizon. This month, researchers have theorised a next-generation transistor based not on silicon but on a ribbon of graphene, a two-dimensional carbon material with the thickness of a single atom. Their findings – reported in Nature Communications – could have big implications for electronics, computing speeds and big data in the future. Graphene-based transistors may someday lead to computers that are 1,000 times faster and use a hundredth of today's power.
"If you want to continue to push technology forward, we need faster computers to be able to run bigger and better simulations for climate science, for space exploration, for Wall Street. To get there, we can't rely on silicon transistors anymore," said Ryan M. Gelfand, director of the NanoBioPhotonics Laboratory at UCF.
University of Central Florida Assistant Professor Ryan M. Gelfand
His team found that by applying a magnetic field to a graphene ribbon, they could change the resistance of current flowing through it. For this device, the magnetic field was controlled by increasing or decreasing the current through adjacent carbon nanotubes. The strength of the magnetic field matched the flow of current through this new kind of transistor, much like a valve controlling the flow of water through a pipe.
Transistors act as on and off switches. A series of transistors in different arrangements act as logic gates, allowing microprocessors to solve complex arithmetic and logic problems. But clock speeds that rely on silicon transistors have been relatively stagnant for over a decade now, and are mostly still stuck in the 3 to 4 gigahertz range.
A cascading series of graphene transistor-based logic circuits could produce a massive jump, explains Gelfland, with clock speeds approaching the terahertz range – 1,000 times faster – because communication between each of the graphene nanoribbons would occur via electromagnetic waves, instead of the physical movement of electrons. They would also be smaller and far more efficient, allowing device-makers to shrink technology and squeeze in more functionality.
"The concept brings together an assortment of existing nanoscale technologies and combines them in a new way," said Dr. Joseph Friedman, assistant professor of electrical and computer engineering at UT Dallas, who collaborated with Gelfland and his team. While the concept is still in the early stages, Friedman said work towards a prototype all-carbon, cascaded spintronic computing system will continue in the NanoSpinCompute research laboratory.
The University of California, Berkeley, has created a device that pulls water from dry air, powered only by the Sun. Even under conditions of relatively low (20-30%) humidity, it can produce 2.8 litres of water over a 12-hour period.
Credit: University of California, Berkeley
Imagine a future in which every home has an appliance that pulls all the water the household needs out of the air, even in dry or desert climates, using only the power of the Sun. That future may be just around the corner, with the demonstration of a water harvester that uses only ambient sunlight to pull litres of water out of the air each day in conditions as low as 20 percent humidity, a level common in arid areas.
The solar-powered harvester, reported in the journal Science, was constructed at the Massachusetts Institute of Technology using a special material called a metal-organic framework – or MOF – produced at the University of California, Berkeley.
"This is a major breakthrough in the long-standing challenge of harvesting water from the air at low humidity," said Omar Yaghi from UC Berkeley, one of two senior authors of the paper. "There is no other way to do that right now, except by using extra energy. Your electric dehumidifier at home 'produces' very expensive water."
The prototype, under conditions of 20-30 percent humidity, was able to pull 2.8 litres (3 quarts) of water from the air over a 12-hour period, using one kilogram (2.2 pounds) of MOF. Rooftop tests at MIT confirmed that the device works in real-world conditions.
Schematic of a metal-organic framework (MOF). Credit: UC Berkeley, Berkeley Lab image.
"One vision for the future is to have water off-grid, where you have a device at home running on ambient solar for delivering water that satisfies the needs of a household," said Yaghi, who is the founding director of the Berkeley Global Science Institute, a co-director of the Kavli Energy NanoSciences Institute and the California Research Alliance by BASF. "To me, that will be made possible because of this experiment. I call it personalised water."
Yaghi worked with Evelyn Wang, a mechanical engineer at MIT, alongside students at the university. The system they designed consists of approximately two pounds of dust-sized MOF crystals compressed between a solar absorber and a condenser plate, inside a chamber open to the air. As ambient air diffuses through the porous MOF, water molecules preferentially attach to the interior surfaces. X-ray diffraction studies have shown that the water vapour molecules often gather in groups of eight to form cubes.
Sunlight entering through a window heats up the MOF and drives the bound water toward the condenser, which is at the temperature of the outside air. The vapour condenses as liquid water and drips into a collector.
"This work offers a new way to harvest water from air that does not require high relative humidity conditions and is much more energy efficient than other existing technologies," said Wang.
This proof of concept harvester leaves much room for improvement, Yaghi said. The current MOF can absorb only 20 percent of its weight in water, but other MOF materials could possibly absorb 40 percent or more. The material could also be tweaked to be more effective at higher or lower humidity.
"It's not just that we made a passive device that sits there collecting water; we have now laid both the experimental and theoretical foundations so that we can screen other MOFs, thousands of which could be made, to find even better materials," he said. "There is a lot of potential for scaling up the amount of water that is being harvested. It is just a matter of further engineering now."
Yaghi and his team are working to improve their MOFs, while Wang continues to improve the harvesting system to produce more water.
"To have water running all the time, you could design a system that absorbs the humidity during the night and evolves it during the day," he said. "Or design the solar collector to allow for this at a much faster rate, where more air is pushed in. We wanted to demonstrate that if you are cut off somewhere in the desert, you could survive because of this device. A person needs about a Coke can of water per day. That is something one could collect in less than an hour with this system."
For the first time, researchers have fabricated printed transistors consisting entirely of two-dimensional nanomaterials.
Credit: AMBER, Trinity College Dublin
Scientists from Advanced Materials and BioEngineering Research (AMBER) at Trinity College, Dublin, have fabricated printed transistors consisting entirely of 2-D nanomaterials for the first time. These materials combine new electronic properties with the potential for low-cost production.
This breakthrough could enable a range of new, futuristic applications – such as food packaging that displays a digital countdown to warn of spoiling, labels that alert you when your wine is at its optimum temperature, or even a window pane that shows the day's forecast. The AMBER team's findings were published yesterday in the leading journal Science.
This discovery opens the path for industry, such as ICT and pharmaceutical firms, to cheaply print a host of electronic devices, from solar cells to LEDs, with applications from interactive smart food and drug labels, to next-generation banknote security and e-passports.
Prof. Jonathan Coleman, an investigator in AMBER and Trinity's School of Physics, commented: "In the future, printed devices will be incorporated into even the most mundane objects such as labels, posters and packaging."
A scene from Steven Spielberg's 2002 sci-fi thriller, Minority Report.
"Printed electronic circuitry (made from the devices we have created) will allow consumer products to gather, process, display and transmit information – for example, milk cartons could send messages to your phone warning that the milk is about to go out-of-date," he continued. "We believe that 2-D nanomaterials can compete with the materials currently used for printed electronics. Compared to other materials employed in this field, our 2-D nanomaterials have the capability to yield more cost effective and higher performance printed devices.
"However, while the last decade has underlined the potential of 2-D materials for a range of electronic applications, only the first steps have been taken to demonstrate their worth in printed electronics. This publication is important, because it shows that conducting, semiconducting and insulating 2-D nanomaterials can be combined together in complex devices. We felt that it was critically important to focus on printing transistors, as they are the electric switches at the heart of modern computing. We believe this work opens the way to print a whole host of devices solely from 2-D nanosheets."
Led by Prof. Coleman, in collaboration with the groups of Prof. Georg Duesberg (AMBER) and Prof. Laurens Siebbeles (TU Delft, Netherlands), the team used standard printing techniques to combine graphene nanosheets as the electrodes with two other nanomaterials, tungsten diselenide and boron nitride as the channel and separator (two important parts of a transistor), to form an all-printed, all-nanosheet, working transistor.
Credit: AMBER, Trinity College Dublin
Printable electronics have developed over the last 30 years based mainly on printable carbon-based molecules. While these molecules can easily be turned into printable inks, such materials are somewhat unstable and have well-known performance limitations. There have been many attempts to surpass these obstacles using alternative materials, such as carbon nanotubes or inorganic nanoparticles, but these materials have also shown limitations in either performance or in manufacturability. While the performance of printed 2-D devices cannot yet compare with advanced transistors, the team believe there is a wide scope to improve performance beyond the current state-of-the-art for printed transistors.
The ability to print 2-D nanomaterials is based on Prof. Coleman's scalable method of producing 2-D nanomaterials, including graphene, boron nitride, and tungsten diselenide nanosheets, in liquids, a method he has licensed to Samsung and Thomas Swan. These nanosheets are flat nanoparticles that are a few nanometres thick, but hundreds of nanometres wide. Critically, nanosheets made from different materials have electronic properties that can be conducting, insulating or semiconducting and so include all the building blocks of electronics. Liquid processing is especially advantageous in that it yields large quantities of high quality 2-D materials in a form that is easy to process into inks. Prof. Coleman's publication provides the potential to print circuitry at extremely low cost, which will facilitate a wide range of applications from animated posters to smart labels.
Prof. Coleman is a partner in Graphene flagship, a €1 billion EU initiative to boost new technologies and innovation during the next 10 years.
Researchers at the University of Manchester have demonstrated a graphene-based sieve able to filter seawater. This could lead to affordable desalination technologies.
Credit: University of Manchester
In recent years, graphene-oxide membranes have attracted major attention as promising candidates for new filtration technologies. Now, the much sought-after breakthrough of making membranes capable of sieving common salts has been achieved. New research demonstrates the real-world potential of providing clean drinking water for millions of people who currently struggle to obtain adequate water resources. The findings, by scientists from the University of Manchester, were published yesterday in the journal Nature Nanotechnology.
Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn't filter common salts, which require even smaller sieves. Previous research at the University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.
The team has now further developed these graphene membranes and found a way to prevent the swelling of the membrane when exposed to water. Pore size in the membrane can be precisely controlled, to filter common salts out of salty water and make it safe to drink.
Man with a bucket of seawater on the coast of Morocco, Africa. Credit: Salvador Aznar
As the effects of climate change continue to impact on water supplies, wealthy countries are also investing in desalination technologies. Following the recent disasters in California, major cities are looking increasingly to alternative water solutions.
When common salts are dissolved in water, they form a 'shell' of water molecules around the salt molecules. This allows the tiny capillaries of the graphene-oxide membranes to block salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast, which is ideal for application of these membranes for desalination.
"To make it permeable, you need to drill small holes in the membrane. But if the hole size is larger than one nanometre, the salts go through that hole," said Rahul Nair, Professor of Materials Physics. "You have to make a membrane with a very uniform, less-than-one-nanometre hole size to make it useful for desalination. It is a really challenging job. When the capillary size is around one nanometre, which is very close to the size of the water molecule, those molecules form a nice interconnected arrangement, like a train."
"Realisation of scalable membranes with uniform pore size down to the atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology," he continued. "This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes."
"The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration, capable of filtering out ions according to their sizes." said Jijo Abraham, co-author on the research paper.
By 2025, the UN expects that 14% of the world's population will encounter water scarcity. This new technology has the potential to revolutionise water filtration across the world, particularly in nations which cannot afford large-scale desalination technology. It is hoped that graphene membrane systems can be utilised on smaller scales – making them accessible to regions that do not have the financial infrastructure to fund large plants.
Researchers from the University of Texas at Austin have developed ultra-flexible, nanoelectronic thread (NET) brain probes, designed to achieve more reliable long-term neural recording than existing probes and without causing scar formation when implanted.
A rendering of the ultra-flexible probe in neural tissue gives viewers a sense of the device’s tiny size and footprint in the brain. Credit: Science Advances.
A team led by assistant professor Chong Xie and research scientist Lan Luan, from the University of Texas at Austin, have developed new probes that have mechanical compliances approaching that of brain tissue and are over 1,000 times more flexible than current neural probes. This ultra-flexibility leads to an improved ability to reliably record and track the electrical activity of individual neurons for long periods of time. There is a growing interest in developing long-term tracking of individual neurons for neural interface applications – such as high-performance prostheses for amputees, as well as new methods of following the progression of neurodegenerative and neurovascular diseases such as stroke, Parkinson's and Alzheimer's.
One of the problems with conventional probes is their size and mechanical stiffness; their larger dimensions and stiffer structures often cause damage around the tissue they encompass. Additionally, while it is possible for the conventional electrodes to record brain activity for months, they often provide recordings that are unreliable and degrade over time. It is also hard for conventional electrodes to track individual neurons for more than a few days.
In contrast, the UT Austin team's electrodes are flexible enough to comply with micro-scale movements of tissue and still stay in place. The probe's size also drastically reduces tissue displacement, so the brain interface is more stable, and the readings are more reliable for longer periods of time. To the researchers' knowledge, this new probe – which is as small as 10 microns at a thickness below 1 micron, and has a cross-section that is only a fraction of that of a neuron or blood capillary – is the smallest neural probe ever developed.
Following tests on mice, the researchers found that the probe's flexibility and size prevented the agitation of glial cells, which is the normal biological reaction to a foreign body and leads to scarring and neuronal loss.
"The most surprising part of our work is that the living brain tissue – the biological system – really doesn't mind having an artificial device around for months," Luan said.
The researchers also used advanced imaging techniques in collaboration with biomedical engineering professor Andrew Dunn and neuroscientists Raymond Chitwood and Jenni Siegel from the Institute for Neuroscience at UT Austin, to confirm that the neural interface did not degrade in the mouse model for over four months of experiments. The researchers plan to continue testing their probes in animal models and hope to eventually engage in clinical testing. Their latest research is published in the journal Science Advances.