Cercetătorii de la MIT au dezvoltat un proces care poate produce fibre ultrafine – în care diametrul este măsurat în nanometri sau miliarde de metri – care sunt extrem de puternice și dure
De-a lungul timpului, poluanții chimici și pe bază de ulei acoperă și împiedică filtrele de apă, ceea ce înseamnă că contaminanții trebuie îndepărtați înainte ca filtrele să înceapă. Testele au arătat că Graphair a continuat să funcționeze chiar și atunci când este acoperit cu poluanț”În Graphair am găsit un filtru perfect pentru purificarea apei, care poate înlocui procesele complexe, consumatoare de timp și cu mai multe etape, necesare în prezent, cu un singur pas”.
În timp ce grafenul este cel mai puternic material din lume și poate fi doar un singur atom de carbon subțire, acesta este, de obicei, hidrofug.
| Posted: Feb 15, 2018 | |
Graphene membranes make Sydney Harbour ‘drinkable’(Nanowerk News) Using their own specially designed form of graphene, ‘Graphair’, CSIRO scientists have supercharged water purification, making it simpler, more effective and quicker. |
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| The new filtering technique is so effective, water samples from Sydney Harbour were safe to drink after passing through the filter. | |
| The breakthrough research was published today in Nature Communications („Anti-fouling graphene-based membranes for effective water desalination”). | |
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| A Graphair sample. (Image: CSIRO) | |
| „Almost a third of the world’s population, some 2.1 billion people, don’t have clean and safe drinking water,” the paper’s lead author, CSIRO scientist Dr Dong Han Seo said. | |
| „As a result, millions – mostly children – die from diseases associated with inadequate water supply, sanitation and hygiene every year. | |
| „In Graphair we’ve found a perfect filter for water purification. It can replace the complex, time consuming and multi-stage processes currently needed with a single step.” | |
| While graphene is the world’s strongest material and can be just a single carbon atom thin, it is usually water repellent. | |
| Using their Graphair process, CSIRO researchers were able to create a film with microscopic nano-channels that let water pass through, but stop pollutants. | |
| As an added advantage Graphair is simpler, cheaper, faster and more environmentally friendly than graphene to make. | |
| It consists of renewable soybean oil, more commonly found in vegetable oil. | |
| Looking for a challenge, Dr Seo and his colleagues took water samples from Sydney Harbour and ran it through a commercially available water filter, coated with Graphair. | |
| Researchers from QUT, the University of Sydney, UTS, and Victoria University then tested and analysed its water purification qualities. | |
| The breakthrough potentially solves one of the great problems with current water filtering methods: fouling. | |
| Over time chemical and oil based pollutants coat and impede water filters, meaning contaminants have to be removed before filtering can begin. Tests showed Graphair continued to work even when coated with pollutants. | |
| Without Graphair, the membrane’s filtration rate halved in 72 hours. | |
| When the Graphair was added, the membrane filtered even more contaminants (99 per cent removal) faster. | |
| „This technology can create clean drinking water, regardless of how dirty it is, in a single step,” Dr Seo said. | |
| „All that’s needed is heat, our graphene, a membrane filter and a small water pump. We’re hoping to commence field trials in a developing world community next year.” | |
| CSIRO is looking for industry partners to scale up the technology so it can be used to filter a home or even town’s water supply. | |
| It’s also investigating other applications such as the treatment of seawater and industrial effluents. |
Folosind acest procedeu simplu, două lichide nemiscibile au produs prima structură torturoasă, cu totul lichidă, cu canale submicrometrice interconectate (mai îngust decât părul uman) și cu o formă persistentă. Astfel de „bijeli” (emulsie bicomponentă blocată) pot avea avantaje ca materiale pentru cataliză și stocare a energiei, dar dificultățile în producerea lor și reducerea dimensiunii canalului au limitat valoarea lor până în prezent.
Această abordare nanoparticulo-surfactant este mai simplă și a condus la bijeli cu dimensiuni canale reglabile – chiar până la zece ori mai mici decât este posibil în prezent. Poate fi utilizată o gamă largă de chimicale și concentrații lichide, nanoparticule și polimeri.
| Posted: Feb 15, 2018 | |
Gel uses nanoparticles for on-demand control of droplet shapes(Nanowerk News) Until now, producing liquids that can be shaped and reshaped on demand hasn’t been possible. Scientists discovered a simple way to form stabilized droplets in a variety of structures. Tightly packed nanoparticle-polymer assemblies at droplet surfaces were squeezed into desired shapes assemblies with an electric field. This new approach is a simple route to form droplets of one liquid phase in another liquid. This could lead to the continuous production of discrete, responsive, and reconfigurable all-liquid systems. |
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| This is a unique platform for printing liquids into structures such as small tubes or special sponge-like gels with desired channel dimensions. This printing can structure, re-organize, and indefinitely lock-in the spatial arrangement of liquids. The result? The printed liquids can create optimized pathways for the flow of mechanical, electrical, or optical energy through a material. Tuning compression at the surface may lead to advanced—even revolutionary—energy storage and catalyst technologies. | |
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| Paralleling your favorite oil-based salad dressing, combining nanoparticles and a soap-like material (surfactant) goes one step further—tunable channels are stabilized in the mixture. Left: A water droplet with a trapped, a.k.a. jammed, nanoparticle-surfactant assembly at its surface. Withdrawing the “water-liking” phase caused the single layer of assemblies to compress. The visible wrinkles developed immediately, suggesting a “solid-like” nature of the squeezed assemblies. And, the process is reversible. Right: A confocal fluorescence image shows the bicontinuous structure of the nanoparticle-surfactant mixtures. (Image: Lawrence Berkeley National Laboratory) | |
| Biological cells compartmentalize the functions of proteins and enzymes within organelles and organize into tissues that coordinate to perform work. Trapping, a.k.a. jamming, nanoparticles at water droplet surfaces offers unparalleled routes to similarly compartmentalize human-made matter resulting in the assembly of structured liquids. | |
| Scientists at Lawrence Berkeley National Laboratory have demonstrated that two liquids that do not mix (called immiscible) can be shaped on demand into stable non-spherical structures. The key is tightly packed nanoparticle surfactants (soap-like materials) at droplet surfaces that are squeezed by an electric field. | |
| A water droplet containing nanoparticles decorated with negatively charged functional groups was first created. The water droplet was in an oil containing polymers with complementary positively charged groups at one end. This allowed the opposite charges to form assemblies at the water-oil interface. An electric field was applied across the droplet, deforming it into an elongated shape with increased surface area. | |
| This allowed more assemblies to form at the droplet surface. Upon removal of the electric field, the droplet attempted to revert to a lower surface area shape (sphere). However, the assemblies were compressed and jammed at the interface. This caused the shape of the liquid to be fixed, “arresting” the liquid in an otherwise highly unstable shape. | |
| Suppressing the instability enables development of a continuous process for forming highly uniform droplets with a wide range of shapes. Moreover, droplet configuration can be controllably changed. Subsequent application of a force such as an electric or magnetic field can cause the droplet to deform. The jammed assemble becomes fluid. This allows its spatial organization to be reconfigured and a new droplet shape to form after removal of the field. | |
| Using this simple process, two immiscible liquids produced the first torturous, all-liquid structure with interconnected sub-micrometer (narrower than a human hair) channels and a persistent shape. Such “bijels” (bicontinuous jammed emulsion) may have advantages as materials for catalysis and energy storage, but difficulties in producing them and reducing the size of their channel have limited their value to date. | |
| This nanoparticle-surfactant approach is simpler and led to bijels with tunable channel sizes—even down to ten times lower than currently possible. A wide range of liquid, nanoparticle, and polymer chemistries and concentrations can be used. | |
| These findings provide valuable guidance for the selection of functionalized nanoparticles and polymers to tune the droplet assembly process to generate structured liquids in a predictable manner. | |
Publications |
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| A. Toor, B. Helms, and T.P. Russell, “Effect of nanoparticle surfactants on the breakup of free-falling water jets during continuous processing of reconfigurable structured liquid droplets.External link” Nano Letters 17, 3119 (2017). [DOI: 10.1021/acs.nanolett.7b00556] | |
| C. Huang, J. Forth, W. Wang, K. Hong, G. Smith, B.A. Helms, and T.P. Russell, “Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactantsExternal link.” Nature Nanotechnology 12, 1060 (2017). [DOI: 10.1038/nnano.2017.182] |
Un concurs de departamente a avansat cinci sisteme de avertizare timpurie destinate detectării atacurilor biologice;sistem pentru a menține atacurile biologice la distanță
Noul sistem, numit un rezonator termic, ar putea permite funcționarea continuă, de ani de zile a sistemelor de teledetecție, de exemplu, fără a necesita alte surse de alimentare sau baterii, spun cercetătorii.echipa a creat o combinație de materiale adaptată cu atenție. Structura de bază este o spumă de metal, realizată din cupru sau nichel, care este apoi acoperită cu un strat de grafen pentru a asigura o conductivitate termică și mai mare. Apoi, spuma este infuzată cu un fel de ceară numită octadecan, un material cu schimbare de fază, care se schimbă între solid și lichid într-un anumit interval de temperatură ales pentru o anumită aplicație.
| Posted: Feb 15, 2018 | |
System draws power from daily temperature swings(Nanowerk News) Thermoelectric devices, which can generate power when one side of the device is a different temperature from the other, have been the subject of much research in recent years. Now, a team at MIT has come up with a novel way to convert temperature fluctuations into electrical power. Instead of requiring two different temperature inputs at the same time, the new system takes advantage of the swings in ambient temperature that occur during the day-night cycle. |
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| The new system, called a thermal resonator, could enable continuous, years-long operation of remote sensing systems, for example, without requiring other power sources or batteries, the researchers say. | |
| The findings are being reported in the journal Nature Communications („Ultra-high thermal effusivity materials for resonant ambient thermal energy harvesting”), in a paper by graduate student Anton Cottrill, Carbon P. Dubbs Professor of Chemical Engineering Michael Strano, and seven others in MIT’s Department of Chemical Engineering. | |
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| The team’s test device, which has been deployed on the roof of an MIT building for several months, was used to prove the principle behind their new energy-harvesting concept. The test device is the black box at right, behind a weather-monitoring system (white) and a set of test equipment to monitor the device’s performance (larger black case at left). (Image: Justin Raymond) | |
| “We basically invented this concept out of whole cloth,” Strano says. “We’ve built the first thermal resonator. It’s something that can sit on a desk and generate energy out of what seems like nothing. We are surrounded by temperature fluctuations of all different frequencies all of the time. These are an untapped source of energy.” | |
| While the power levels generated by the new system so far are modest, the advantage of the thermal resonator is that it does not need direct sunlight; it generates energy from ambient temperature changes, even in the shade. That means it is unaffected by short-term changes in cloud cover, wind conditions, or other environmental conditions, and can be located anywhere that’s convenient — even underneath a solar panel, in perpetual shadow, where it could even allow the solar panel to be more efficient by drawing away waste heat, the researchers say. | |
| The thermal resonator was shown to outperform an identically sized, commercial pyroelectric material — an established method for converting temperature fluctuations to electricity — by factor of more than three in terms of power per area, according to Cottrill. | |
| The researchers realized that to produce power from temperature cycles, they needed a material that is optimized for a little-recognized characteristic called thermal effusivity — a property that describes how readily the material can draw heat from its surroundings or release it. Thermal effusivity combines the properties of thermal conduction (how rapidly heat can propagate through a material) and thermal capacity (how much heat can be stored in a given volume of material). In most materials, if one of these properties is high, the other tends to be low. Ceramics, for example, have high thermal capacity but low conduction. | |
| To get around this, the team created a carefully tailored combination of materials. The basic structure is a metal foam, made of copper or nickel, which is then coated with a layer of graphene to provide even greater thermal conductivity. Then, the foam is infused with a kind of wax called octadecane, a phase-change material, which changes between solid and liquid within a particular range of temperatures chosen for a given application. | |
| A sample of the material made to test the concept showed that, simply in response to a 10-degree-Celsius temperature difference between night and day, the tiny sample of material produced 350 millivolts of potential and 1.3 milliwatts of power — enough to power simple, small environmental sensors or communications systems. | |
| “The phase-change material stores the heat,” says Cottrill, the study’s lead author, “and the graphene gives you very fast conduction” when it comes time to use that heat to produce an electric current. | |
| Essentially, Strano explains, one side of the device captures heat, which then slowly radiates through to the other side. One side always lags behind the other as the system tries to reach equilibrium. This perpetual difference between the two sides can then be harvested through conventional thermoelectrics. The combination of the three materials — metal foam, graphene, and octadecane — makes it “the highest thermal effusivity material in the literature to date,” Strano says. | |
| While the initial testing was done using the 24-hour daily cycle of ambient air temperature, tuning the properties of the material could make it possible to harvest other kinds of temperature cycles, such as the heat from the on-and-off cycling of motors in a refrigerator, or of machinery in industrial plants. | |
| “We’re surrounded by temperature variations and fluctuations, but they haven’t been well-characterized in the environment,” Strano says. This is partly because there was no known way to harness them. | |
| Other approaches have been used to try to draw power from thermal cycles, with pyroelectric devices, for example, but the new system is the first that can be tuned to respond to specific periods of temperature variations, such as the diurnal cycle, the researchers say. | |
| These temperature variations are “untapped energy,” says Cottrill, and could be a complementary energy source in a hybrid system that, by combining multiple pathways for producing power, could keep working even if individual components failed. The research was partly funded by a grant from Saudi Arabia’s King Abdullah University of Science and Technology (KAUST), which hopes to use the system as a way of powering networks of sensors that monitor conditions at oil and gas drilling fields, for example. | |
| “They want orthogonal energy sources,” Cottrill says — that is, ones that are entirely independent of each other, such as fossil fuel generators, solar panels, and this new thermal-cycle power device. Thus, “if one part fails,” for example if solar panels are left in darkness by a sandstorm, “you’ll have this additional mechanism to give power, even if it’s just enough to send out an emergency message.” | |
| Such systems could also provide low-power but long-lasting energy sources for landers or rovers exploring remote locations, including other moons and planets, says Volodymyr Koman, an MIT postdoc and co-author of the new study. For such uses, much of the system could be made from local materials rather than having to be premade, he says. | |
| This approach “is a novel development with a great future,” says Kourosh Kalantar-zadeh, a distinguished professor of engineering at RMIT University in Melbourne, Australia, who was not involved in this work. “It can potentially play an unexpected role in complementary energy harvesting units.” | |
| He adds, “To compete with other energy harvesting technologies, always higher voltages and powers are demanded. However, I personally feel that it is quite possible to gain a lot more out of this by investing more into the concept. … It is an attractive technology which will be potentially followed by many others in the near future.” |
| Source: By David L. Chandler, MIT |
Exoskeletonele mobile sunt mașini portabile care sunt mobile și alimentate cu ajutorul unui sistem de hidraulică, motoare electrice, pneumatice, pârghii sau o combinație de tehnologii care permit mișcarea membrelor cu rezistență și rezistență
armata va lua doi Humvee înarmați, autonomi, pe o pistă pentru a le testa și a le certifica drept vehicule de luptă, ceea ce le va face primele vehicule de teren robotizate pentru a fi OK
au dezvoltat noi materiale nețesute care sunt conductive din punct de vedere electric, precum și flexibile și respirabile. Acest lucru deschide calea pentru hainele confortabile de înaltă tehnologie care, de exemplu, transformă lumina soarelui în căldură, pun la dispoziție dispozitive electronice portabile cu electricitate sau conțin senzori pentru antrenament de fitness.au reușit să producă materiale nețesute conductive din punct de vedere electric care au toate celelalte caracteristici pe care le-ați aștepta de la îmbrăcămintea potrivită pentru utilizarea zilnică. Materialele sunt flexibile și, astfel, se adaptează mișcărilor și modificărilor posturii. În plus, ele sunt permeabile la aer, ceea ce înseamnă că nu interferează cu respirația naturală a pielii.
| Posted: Feb 14, 2018 | |
Smart and comfortable new nanocomposite textiles for high-tech clothing(Nanowerk News) Uncomfortable, rigid, with low air permeability: textile materials capable of conducting electricity can be awkward for day-to-day use. However, researchers at the University of Bayreuth, Donghua University in Shanghai, and Nanjing Forestry University have now developed new nonwoven materials that are electrically conductive as well as flexible and breathable. This paves the way for comfortable high-tech clothes which, for example, convert sunlight to warmth, supply wearable electronic devices with electricity, or contain sensors for fitness training. |
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| The scientists have published their findings in the journal npj Flexible Electronics („Polymer nanofibre composite nonwovens with metal-like electrical conductivity”). | |
| Prof. Dr. Andreas Greiner’s team of researchers at the University of Bayreuth and their Chinese partners have succeeded in producing electrically conductive nonwovens which have all the other characteristics you would expect from clothing that is suitable for daily use. The materials are flexible, and thus adapt to movements and changes in posture. In addition, they are air-permeable, meaning they do not interfere with the natural breathing of the skin. | |
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| Prof. Dr. Andreas Greiner (left) and Prof. Dr. Seema Agarwal (right) with equipment for electrospinning at the University of Bayreuth. With backlighting, one can see the thin fibres from which nonwoven materials are formed. | |
| The combination of these properties is based on a special production process. In contrast to common methods of production, metal wires were not inserted into finished textiles. Rather, the scientists modified classical electro-spinning, which has been used to produce nonwovens for many years: short electro-spun polymer fibres and small amounts of tiny silver wires with a diameter of only 80 nanometres are mixed in a liquid. Afterwards, they are filtered, dried, and briefly heated up. If the composition is right, the resulting nonwoven material exhibits a very high degree of electrical conductivity. | |
| This opens up a whole range of possibilities for innovative applications, especially in the area of smart clothes (i.e. wearables). Everyday clothing, for example, can be equipped with solar cells such that the captured sunlight is converted to warmth, heating up the textiles themselves. Mobile phones, cameras, mini-computers, and other wearable electronic devices could be charged by plugging them into the textiles. Sensors installed in the clothes could provide athletes and trainers with important fitness and health data or could give family and friends information on its location. | |
| “In addition to articles of clothing, similar functions could also just as easily be installed in textile materials for use in seats and instruments in cars or airplanes,” explained Prof. Dr. Andreas Greiner, Chair of Macromolecular Chemistry II at the University of Bayreuth. | |
| “Our approach, which takes the production of conductive textiles as its basis, can in principle be applied to many different systems,” added Steffen Reich, doctoral researcher and lead author of the new study. As an example, he cites current Bayreuth research projects on microbial fuel cells, which could eventually be used as electrodes in such nonwoven materials. | |
| The research findings that were published in npj Flexible Electronics resulted from close cooperation between the University of Bayreuth, Donghua University in Shanghai, and Nanjing Forestry University. It was only two years ago that the University of Bayreuth signed a cooperation agreement with Donghua University, which has had a research priority on the research and development of textiles since the establishment of the institution. The mutual exchange in research and teaching that was agreed on is now beginning to bear fruit. |
| Source: University of Bayreuth |
proliferarea radiourilor, a dispozitivelor inteligente portabile, a GPS-ului și a altor dispozitive electronice personale care susțin operațiunea „viitorului soldat” promite examinarea modalităților de a satisface cererea de energie și de energie la nivelul soldaților;
Incomod, rigid, cu permeabilitate scăzută a aerului: materialele textile capabile să conducă electricitatea pot fi dificil de utilizat pentru utilizarea zilnică;fibrele subțiri din care se formează materiale nețesute;
Combinația acestor proprietăți se bazează pe un proces de producție special
demonstrează modul în care senzorii purtați pot să urmărească mișcarea ochilor;inginerii au transformat hârtia de țesut, asemănătoare cu cea a toaletei, într-un nou tip de senzor care poate detecta un impuls, o clipire a ochiului și alte mișcări umane
