Dar oficialii militari caută din greu posibilitatea de a dezvolta sisteme robotice capabile să acționeze singure în cazul în care controlul la distanță este întrerupt și trebuie luate decizii cu privire la desfășurarea unei arme
Distruge toate formele de viata bazate pe carbon ar fi un algoritm foarte prost pentru omorurile autonome
Pentru proiectul lor, grupul Ramprasad sa uitat la polimeri din doar șapte blocuri: CH 2 , C 6 H 4 , CO, O, NH, CS și C 4 H 2 S (S este sulf). Acestea se găsesc în materiale plastice obișnuite, cum ar fi polietilenă, poliesteri și poliuree. O varietate enormă de polimeri ar putea fi construită teoretic folosind doar aceste blocuri de construcție; Grupul Ramprasad a decis la început să analizeze doar 283, fiecare compus dintr-o unitate repetată de patru blocuri.
| Posted: Mar 04, 2016 | |
Building a better mouse trap, from the atoms up(Nanowerk News) For most of human history, the discovery of new materials has been a crapshoot. But now, UConn researchers have systematized the search with machine learning that can scan millions of theoretical compounds for qualities that would make better solar cells, fibers, and computer chips. The search for new materials may never be the same. |
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| No one knows why an early metallurgist decided to smelt a hunk of tin into some copper, but the resulting bronze alloy was harder and more durable than any material previously known. Most materials experimentation over the ensuing 7,000 years has been similarly random, guided largely by philosophy and chemical intuition. | |
| But in a world that contains at least 95 stable elements – the basic building blocks of matter – the number of possible combinations is enormous, and experimentation is an awfully inefficient way to find what you’re looking for. | |
| Enter UConn materials scientist Ramamurthy ‘Rampi’ Ramprasad. Instead of randomly mixing chemicals to see what they do, Ramprasad designs them rationally, using machine learning to figure out which atomic configurations make a polymer a good electrical conductor or insulator. | |
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| The Ramprasad Lab is employing machine learning to design new materials without having to pre-test each one. (Schematic by Chiho Kim, Ramprasad Lab) | |
| A polymer is a large molecule made of many repeating building blocks. Polymers are very common in both living and man-made materials. Probably the most familiar example is plastics, and the wide variation in plastics – which can be hard, soft, stretchy, brittle, spongy, clear, opaque or translucent – gives an inkling of how diverse polymers in general can be. | |
| Polymers can also have diverse electronic properties. For example, they can be very good insulators – preventing electrons, and thus electric current, from traveling through them – or good conductors, allowing electricity to pass through them freely. And what controls all these properties is mainly how the atoms in the polymer connect to each other. But until recently, no one had systematically related properties to atomic configurations. | |
| So Ramprasad and his colleagues decided to do just that. First, they would analyze known polymers, using laborious but accurate quantum mechanics-based calculations to figure out which arrangements of atoms confer which properties, and quantify those atomic-level relationships via a string of numbers that fingerprint each polymer. Once they had those, they could have a computer search through any number of theoretical polymers to figure out which ones might have which properties. Then anyone looking for a polymer with a certain property could quickly scan the list and decide which theoretical polymers might be worth trying. | |
| Many polymers are made of building blocks containing just a few atoms. For instance, polyurea, a common plastic, has as the basic structure a repeating sequence of nitrogen (N), hydrogen (H) and oxygen (O): NH-O-NH-O. Most polymers look like that, made of carbon (C), H, N and O, with a few other elements thrown in occasionally. | |
| For their project, Ramprasad’s group looked at polymers made of just seven building blocks: CH2, C6H4, CO, O, NH, CS, and C4H2S (the S is sulfur). These are found in common plastics such as polyethylene, polyesters, and polyureas. An enormous variety of polymers could theoretically be constructed using just these building blocks; Ramprasad’s group decided at first to analyze just 283, each composed of a repeated four-block unit. | |
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| Polyurea, a common plastic. In this diagram, N is nitrogen, H hydrogen, and O oxygen. R stands in for any number of chemicals that could slightly alter the polymer, but the repeating NH-O-NH-O is the basic structure. Most polymers look like that, made of carbon (C), H, N and O, with a few other elements thrown in occasionally. (By Yikrazuul – own work, public domain) | |
| They started from basic quantum mechanics, and calculated the three-dimensional atomic and electronic structures of each of those 283 four-block polymers. This is not trivial: calculating the position of every electron and atom in a molecule with more than two atoms takes a powerful computer a significant chunk of time, which is why they did it for only 283 molecules. | |
| Once they had the three-dimensional structures, they could calculate what they really wanted to know: each polymer’s properties. They calculated the band gap, which is the amount of energy it takes for an electron in the polymer to break free of its home atom and travel around the material, and the dielectric constant, which is a measure of the effect an electric field can have on the polymer. These properties translate to how much electric energy each polymer can store in itself. The researchers used established techniques that have long been known. They take a prohibitive amount of computing time, which is why it’s so hard to evaluate materials this way. | |
| Ramprasad’s group then went one step further. They wanted a shorthand system that a computer could use to look at the building blocks of a polymer and how they connect to each other, and make educated guesses about its properties. | |
| Computers deal with numbers, so first they had to define each polymer as a string of numbers, a sort of numerical fingerprint. Since there are seven possible building blocks, there are seven possible numbers, each indicating how many of each block type are contained in that polymer. But a simple number string like that doesn’t give enough information about the polymer’s structure, so they added a second string of numbers that tell how many pairs there are of each combination of building blocks, such as NH-O or C6H4-CS. Still not quite enough information, so they added a third string that described how many triples, like NH-O-CH2, there were. They arranged these strings as a three-dimensional matrix, which is a convenient way to describe such strings of numbers in a computer. | |
| Then they let the computer go to work. Using the library of 283 polymers they had laboriously calculated using quantum mechanics, the machine compared each polymer’s numerical fingerprint to its band gap and dielectric constant, and gradually ‘learned’ which building block combinations were associated with which properties. It could even map those properties onto a two-dimensional matrix of the polymer building blocks. | |
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| Once the machine learned which atomic building block combinations gave which properties, it no longer needed the quantum mechanics calculations of atomic structure. It could accurately evaluate the band gap and dielectric constant for any polymer made of any combination of those seven building blocks, using just the numerical fingerprint of its structure. | |
| Many of the predictions of quantum mechanics and the machine learning scheme have been validated by Ramprasad’s UConn collaborators, chemistry professor Greg Sotzing and electrical engineering professor Yang Cao. Sotzing actually made several of the novel polymers, and Cao tested their properties; they came out just as Ramprasad’s computations had predicted. | |
| „What’s most surprising is the level of accuracy with which we can make predictions of the dielectric constant and band gap of a material using machine learning. These properties are generally computed using quantum mechanical methods such as density functional theory, which are six to eight orders of magnitude slower,” says Ramprasad. The group published a paper on their polymer work in Scientific Reports on Feb. 15 („Machine Learning Strategy for Accelerated Design of Polymer Dielectrics”); and another paper that utilizes machine learning in a different manner, namely, to discover laws that govern dielectric breakdown of insulators, will be published in a forthcoming issue of Chemistry of Materials. | |
| But even if you don’t have access to those academic journals, you can see the predicted properties of every polymer Ramprasad’s group has evaluated in their online data vault, Khazana (khazana.uconn.edu), which also provides their machine learning apps to predict polymer properties on the fly. They are also uploading data and the machine learning tools from their Chemistry of Materials work, and from an additional recent article published in Scientific Reports on Jan. 19 on predicting the band gap of perovskites, inorganic compounds used in solar cells, lasers, and light-emitting diodes. | |
| As a theoretical materials scientist, what Ramprasad wants to know is why materials behave the way they do. What about a polymer makes its dielectric constant just so? Or what makes an insulator withstand enormous electric fields without breaking down? But he also wants this understanding to be put to work to design new useful materials rationally. So he makes the results of his calculations freely available in the hope that someone else might look through them, see one, and go, „Wow. I’m looking for a material with exactly those properties!” and then make it. If it works as predicted, they’re both happy. |
| Source: University of Connecticut |
În viitor, grafenul ar putea fi folosit ca strat de acoperire extrem de subțire, rezultând o pierdere de energie aproape între zero între piesele mecanice. Aceasta se bazează pe lubrifiția excepțional de mare – sau așa-numita super-lubricitate – a carbonului modificat sub formă de grafen. Aplicarea acestei proprietăți la dispozitivele mecanice și electromecanice nu numai că ar îmbunătăți eficiența energetică, ci și va prelungi considerabil durata de viață a echipamentului.
| Posted: Mar 04, 2016 | |
Graphene slides smoothly across gold(Nanowerk News) Since it produces almost no friction at all, graphene could drastically reduce energy loss in machines when used as a coating, as researchers report in the journal Science („Superlubricity of graphene nanoribbons on gold surfaces”). |
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| A graphene nanoribbon was anchored at the tip of an atomic force microscope and dragged over a gold surface. The observed friction force was extremely low. (Image: University of Basel, Department of Physics) | |
| In future, graphene could be used as an extremely thin coating, resulting in almost zero energy loss between mechanical parts. This is based on the exceptionally high lubricity–or so-called superlubricity–of modified carbon in the form of graphene. Applying this property to mechanical and electromechanical devices would not only improve energy efficiency but also considerably extend the service life of the equipment. | |
| Fathoming out the causes of the lubricant behavior | |
| An international community of physicists have studied the above-average lubricity of graphene using a two-pronged approach combining experimentation and computation. To do this, they anchored two-dimensional strips of carbon atoms–so-called graphene nanoribbons–to a sharp tip and dragged them across a gold surface. Computer-based calculations were used to investigate the interactions between the surfaces as they moved across one another. Using this approach, the research team is hoping to fathom out the causes of superlubricity; until now, little research has been carried out in this area. | |
| By studying the graphene nanoribbons, the researchers hope to learn about more than just the slip behavior. Measuring the mechanical properties of the carbon-based material also makes sense because it offers excellent potential for a whole range of applications in the field of coatings and micromechanical switches. In future, even electronic switches could be replaced by nanomechanical switches, which would use less energy for switching on and off than conventional transistors. | |
| The experiments revealed almost perfect, frictionless movement. It is possible to move graphene nanoribbons with a length of 5 to 50 nanometers using extremely small forces (2 to 200 piconewtons). There is a high degree of consistency between the experimental observations and the computer simulation. | |
| A discrepancy between the model and reality appears only at greater distances (five nanometers or more) between the measuring tip and the gold surface. This is probably because the edges of the graphene nanoribbons are saturated with hydrogen, which was not accounted for in the simulations. | |
| „Our results help us to better understand the manipulation of chemicals at the nano level and pave the way for creating frictionless coatings,” write the researchers. |
| Source: Technische Universität Dresden |
Read more: Graphene slides smoothly across gold
Ei au dezvoltat folii de iluminat flexibile, care pot fi produse în role roll-to-roll – la fel ca ziarele tipărite. Aceste dispozitive deschid calea spre celulele solare mai ieftine și panourile de iluminat cu LED-uri.noi materiale electrozide transparente și barieră pentru a fi utilizate în următoarea generație de optoelectronică flexibilă. Trei dintre aceste substraturi pe bază de electrozi care utilizează nanotuburi de carbon, fibre metalice sau argint subțire sunt fie deja produse comercial, fie se așteaptă să fie astfel de anul acesta.
| Posted: Mar 04, 2016 | |
Technological breakthrough for cheaper lighting and flexible solar cells(Nanowerk News) In more than three years of work european scientists finally made future lighting technology ready to market. They developed flexible lighting foils that can be produced roll-to-roll – much like newspapers are printed. These devices pave the path towards cheaper solar cells and LED lighting panels. The project named TREASORES was led by Empa scientist Frank Nüesch and combined knowhow from nine companies and six research institutes in five european countries. |
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| Flexible OLED light sources on transparent electrodes developed within TREASORES. These OLEDs were made by Fraunhofer FEP using a roll-to-roll process. (Image: Fraunhofer FEP) | |
| In November 2012, the TREASORES project (Transparent Electrodes for Large Area Large Scale Production of Organic Optoelectronic Devices) started with the aim of developing technologies to dramatically reduce the production costs of organic electronic devices such as solar cells and LED lighting panels. Funded with 9 million Euro from the European Commission and an additional 6 million Euros from the project partners, the project has since then produced seven patent applications, a dozen peer-reviewed publications and provided inputs to international standards organisations. | |
| New transparent electrodes and barrier materials | |
| Most importantly, the project has developed and scaled up production processes for several new transparent electrode and barrier materials for use in the next generation of flexible optoelectronics. Three of these electrodes-on-flexible substrates that use either carbon nanotubes, metal fibres or thin silver are either already being produced commercially, or expected to be so as of this year. | |
| The new electrodes have been tested with several types of optoelectronic devices using rolls of over 100 meters in length, and found to be especially suitable for next-generation light sources and solar cells. The roll of OLED light sources with the project logo was made using roll-to-roll techniques at Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (Fraunhofer FEP) on a thin silver electrode developed within the project by Rowo Coating GmbH. | |
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| Flexible fabric electrodes were produced in a roll-to-roll process by incorporated woven metallic wires. This results in a transparent and flexible electrode with very low electrical resistivity and high total optical transmission throughout the visible and near infrared spectrum. (Image: Sefar AG) | |
| Flexible light sources for cheap and nice illumination | |
| Such processing techniques promise to make light sources and solar cells much cheaper in future, but require flexible and transparent electrodes and water impermeable barriers – which have also been developed by the TREASORES project. | |
| The electrodes from the project are technically at least as good as those currently used (made from indium tin oxide, ITO) but will be cheaper to manufacture and do not rely on the import of indium. Tomasz Wanski from the Fraunhofer FEP said that because of the new electrodes, the OLED light source was very homogeneous over a large area, achieving an efficiency of 25 lumens per watt – as good as the much slower sheet to sheet production process for equivalent devices. | |
| In the course of the project, new test methods were developed by the National Physical Laboratory in the UK to make sure that the electrodes would still work after being repeatedly bent – a test that may become a standard in the field. | |
| Special foils protect from oxygen | |
| A further outcome of the project has been the development, testing and production scale-up of new approaches to transparent barrier foils (plastic layers that prevent oxygen and water vapour from reaching the sensitive organic electronic devices). High performance low-cost barriers were produced and it is expected that the Swiss company Amcor Flexibles Kreuzlingen will adopt this technology after further development. | |
| Such high performance barriers are essential to achieve the long device lifetimes that are necessary for commercial success – as confirmed by a life cycle analysis (LCA) completed during the project, solar cells are only economically or ecologically worthwhile if both their efficiency and lifetime are high enough. By combining the production of barriers with electrodes (instead of using two separate plastic substrates), the project has shown that production costs can be further reduced and devices made thinner and more flexible. | |
| The main challenge the project had to face was to make the barrier and electrode foils extremely flat, smooth and clean. Optoelectronic devices have active layers of only a few hundred nanometres (less than one percent of the width of a human hair), and even small surface irregularities or invisibly tiny dust particles can ruin the device yield or lead to uneven illumination and short lifetimes. | |
| Knowhow form 15 partners in five nations combined | |
| The TREASORES project united nine companies with six research institutes from five countries and was led by Frank Nüesch from the Swiss Federal Laboratories for Materials Science and Technology (Empa). ”I am very much looking forward to seeing the first commercial products made using materials from the project in 2016”, says Nüesch. | |
| Michael Niggemann, Chief Technology Officer for Eight19 Ltd in the United Kingdom said: ”The TREASORES project was a success for Eight19 as it made a significant contribution to the reduction in manufacturing cost of Eight19’s plastic solar cells. This was achieved through the customized development and up-scaling of low cost barriers and electrodes in the project consortium. It is an essential step towards the commercialization of Eight19’s organic photovoltaic based on technology developed and produced in Europe.” |
| Source: Empa |
Read more: Technological breakthrough for cheaper lighting and flexible solar cells
Comorile ascunse din Agenda aeriană TechNet
Imaginile și videoclipurile recodate de camerele 3D ar putea fi proiectate într-o bună zi ca holograme – deși protecția este o provocare totală diferită
graphene este un material minunat înconjurat de așteptări mari
pielea poate să se întindă, să atingă sens și să emită lumină
o piele artificiala care se poate intinde, simti presiunea si emite lumina,
echipa a dezvoltat un nanopen simplu pentru desenarea și plasarea nanometrică a moleculelor singulare sau multiple, cum ar fi tijele. Acest lucru este exemplificat în lucrare printr-un accent pe nanotuburile de carbon, considerat pe scară largă ca un element critic în electronica moleculară.
Posted: Mar 02, 2016
(Nanowerk Spotlight) One of the fundamental challenges in the development of nanoelectromechanical systems (NEMS) – and of nanotube- and nanowire-based devices in general – is the large-scale controlled placement of molecular sized building blocks on a substrate.The ability to effectively place at will molecules so that they can be rapidly organized into functional components is a core requirement of many nanotechnology applications, components and functional devices.In new work, an international team of researchers describes the drawing and Raman characterization procedure developed for placing single-walled carbon nanotubes (SWCNTs), proof of SWCNT alignment, optimization of the drawing parameters, and the subsequent placement in predefined lithographic structures for the demonstration of electrical conductivity.The findings have been published in the January 20, 2016 online edition of Nano Letters („Nanodrawing of Aligned Single Carbon Nanotubes with a Nanopen”).In essence, the team developed a simple nanopen for drawing and placing aligned single or multiple rod like molecules nanometrically. This is exemplified in the paper by a focus on carbon nanotubes, considered widely as a critical element in molecular electronics.
Controlled direct drawing of SWCNTs on SiO2. (a) A diagrammatic representation of the drawing process. The SWCNT alignment occurs by capillary forces in the direction of drawing. (b) Raman mapping of the written structure of the G+ band together with (c) a Raman spectrum at a point in this image. (d) AFM of the written structure before washing with (e) a line scan of a particular location. The height of the drawing is 200-250 nm, and the line width is 600-800 nm. (f) AFM of a portion of the written structure that has been washed after 4 days of drying, with (g) a line scan at a particular location. After washing only the SWCNTs remained on the substrate with the associated surfactant and solution being washed away. The height of the drawn structure is between 0.8 and 2.9 nm. (Reprinted with permission by American Chemical Society)”The basis of the methodology, which is the use of capillary forces during nanowriting of chemicals, should have general applicability in many areas such as polymer molecules, DNA where molecular placement is fundamentally and technologically of considerable import, nanoparticle manometric deposition, the deposition of metallic lines etc.,” Aaron Lewis, a professor at The Hebrew University of Jerusalem, Israel, tells Nanowerk.Thus, from the point of view of the paper, it is now feasible to write molecular components into circuit functionalities. As Mark Ratner from Northwestern commented a few years ago: „Connecting molecular nanowires in a controlled fashion to single molecules that function like circuit elements is one of the great challenges of the field (of molecular electronics).””The fundamental implications of our work is that we present a general method of chemical nanowriting that is applicable to any surface hydrophobic or hydrophilic, rough or smooth, with liquid or with gases,” Lewis points out.The team’s fountain pen nanolithography (FPN) method uses a simple glass cantilever as a nanofountain pen to draw a carbon nanotube solution directly onto a substrate with atomic force feedback.The SWCNTs are deposited and aligned by capillary forces in the drawing direction at a speed of microns per second.”FPN has overtones of the dip pen nanolithography (DPN) method but has some powerful advantages,” explains Lewis. „FPN does not have DPNs preference for hydrophilic substrates like gold and does not need to deposit linker molecules for deposition of SWCNTs as is the case in DPN. In addition, the nanopens used in FPN are optically transparent and have their drawing tip highly exposed to the optical axis for accurate placement within a device structure.”Potential application areas for FPN are molecular circuit design; mask repair at the highest of resolutions by either adding or removing with a solvent and the nanopen errors in the mask; flat panel display repair of electronic components with molecular of nanoparticle inks; placement of structured defects in photonic band gap or plasmonic optical components for guiding light in specific directions more effectively.The team is planning to demonstrate the broadened scope of this method for many different directions in science and technology.”Basically, what we have shown for carbon nanotubes now needs to be applied to other molecular systems,” says Lewis. „However, not only in terms of writing recipes for these systems on any surface but characterizing such things as the ability to write on a structure already previously drawn by the Nanopen. This among many other features is unique to this method.”By Michael Berger – Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny. Copyright © Nanowerk
Read more: Writing nanotubes with a nano fountain pen
un singur LED este necesar pentru fiecare punct de lumină
