Desirable defects in liquid crystals

Introducing flaws into liquid crystals by inserting microspheres and then controlling them with electrical fields: that, in a nutshell, is the rationale behind a method that could be exploited for a new generation of advanced materials, potentially useful for optical technologies, electronic displays and e-readers. A team of scientists (including research fellows at the International School for Advanced Studies, SISSA, in Trieste) has just published a paper in the journal ("Field-controlled columnar and planar patterning of cholesteric colloids") where they describe just how this approach works and provide the results of a computer simulation. Colloids in liquid crystals Colloids in liquid crystals. “Generally, flaws are the last thing you’d want in a liquid crystal”, explains Giuseppe D’Adamo, postdoctoral fellow at SISSA. “However, this new method allows us to exploit the defects in the material to our advantage”. D’Adamo is first author of a paper just published in Physical Review Letters. The study made computer models of colloidal suspensions in liquid crystals subjected to electrical fields modulated over time. Colloids are particles in suspension (i.e., a condition halfway between dispersion and solution) in a liquid. These composite materials have been receiving plenty of attention for their optical properties for some time now, but the use of electrical fields to modify them at will is an absolute novelty. “Our simulations demonstrate that by switching on or off an electrical field of appropriate intensity we can re-order the colloids by arranging them into columns or planes”, comments Cristian Micheletti of SISSA, co-author of the paper. “This easy-to-control plasticity could make the material suitable for optical-electronic devices such as e-readers, for example”. Liquid crystals are particular types of liquids. In a normal liquid, molecules have no systematic arrangement and, viewed from any angle, they always appear the same. The molecules forming liquid crystals, by contrast, are arranged in precise patterns often dictated by their shape. To get an idea of what happens in a liquid crystal, imagine a fluid made up of tiny needles which, instead of being arranged chaotically, all point in the same direction. This also means that if we look at the liquid from different viewpoints it will change in appearance, for example it might appear lighter or darker (have you ever seen this happen in LCD monitors, especially the older models?). “The useful natural tendency of liquid crystal molecules to spontaneously arrange themselves in a certain pattern can be counteracted by introducing colloids in the fluid. In our case, we used microscopic spherical particles, which ‘force’ the molecules coming into contact with their surface to adapt and rotate in a different direction” explains D’Adamo. “This creates ‘defect lines’ in the material, i.e., circumscribed variations in the orientation of molecules which result in a local change in the optical properties of the medium”. More in detail... These defect lines have an important effect: they enable remote interactions among colloidal particles, by holding them together as if they were thin strings. “Liquid crystal molecules tend to align along the electrical field. By switching the field on and off we create competition between the spontaneous order of the liquid crystal, the order dictated by the surface of the colloidal particles and, finally, the order created by the electrical potential”, says Micheletti. “This competition produces many defect lines that act on the colloids by moving them or clustering them”. “It’s a bit like pulling the invisible strings of a puppet: by carefully modulating the electrical fields we can, in principle, make all the particles move and arrange them as we like, by creating defect lines with the shape we want” continues D’Adamo. “An important detail is that the colloidal configurations are metastable, which means that once the electrical field has been switched off the colloids remain in their last position for a very long time”. In brief, this implies that the system only requires energy when it changes configuration, a major saving. “In this respect, the method works like the electronic ink used in digital readers, and it would be interesting to explore its applicability in this sense”, concludes Micheletti. The study, carried out with the collaboration of SISSA, the University of Edinburgh and the University of Padova, has been included as an Editors’ Suggestion among the Highlights of the journal .
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Making magnetic hot spots with pairs of silicon nanocylinders

Shining visible light on two tiny silicon cylinders, or a ‘nanodimer’, placed just 30 nanometers apart, produces resonant hot spots for both the electric and magnetic fields, finds a study by A*STAR researchers (, "Magnetic and Electric Hotspots with Silicon Nanodimers"). This phenomenon could potentially be used to connect computing devices. Two nanocylinders produce resonant electric (E) and magnetic (H) fields when excited with visible light. Two nanocylinders produce resonant electric (E) and magnetic (H) fields when excited with visible light. Earlier theoretical work had predicted the existence of such magnetic hot spots, but this is the first time that they have been observed experimentally with visible light in a nanodimer configuration (see image), according to lead author Reuben Bakker from the A*STAR Data Storage Institute. The researchers numerically calculated the expected electric and magnetic resonances and found good agreement with the experimental results. The use of light to carry information, known as photonics, is critical to the continued growth of information technology. Unfortunately, the diffraction limit of light restricts it from being directed at dimensions smaller than half its wavelength, which imposes a limit on the minimum sizes of photonics-based devices. The use of plasmon resonances in metals — resonant collective oscillations of conduction electrons — has been proposed as a way to overcome this limit. However, metals that support plasmons are often ‘lossy’, which means that the distance the light can travel in them is quite limited. “Typically in metal photonics, researchers have been studying the electric field,” says Bakker. “But we are now looking at materials in the subwavelength regime (below the diffraction limit), where we can create and manipulate the magnetic field as well. Essentially, the electric field creates a current loop inside the nanoparticle and this current loop creates the magnetic resonance.” Being able to manipulate the magnetic field close to the nanodimer provides “another lever to pull so that light does what we want it to do,” says Bakker. To exploit this effect, the nanoparticles need to be made of a high-dielectric-constant material, such as silicon. “We’ve taken the silicon direction because it has a high refractive index and doesn’t have the losses that metals do,” says Bakker. “But silicon may not be the final answer. We know how to work with silicon because of the integrated circuit industry and it is good — but is it the best? We’re still figuring that out.” Bakker sees this work as a step toward more complex systems that could potentially end up as being nanoantennas or waveguide systems. “This nanodimer is an intermediary — it’s not the most useful device in itself. We have to build up our understanding of these systems on an incremental basis,” he says.
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Harnessing sunlight more effectively with nanoparticles

A*STAR researchers have performed theoretical calculations to explain why semiconductor microspheres embedded with metal nanoparticles are so good at using sunlight to catalyze reactions (, "Interference-Induced Broadband Absorption Enhancement for Plasmonic-Metal@Semiconductor Microsphere as Visible Light Photocatalyst"). Analysis of the electric field inside a semiconductor microparticle containing a metal nanoparticle reveals enhanced absorption of sunlight Analysis of the electric field inside a semiconductor microparticle containing a metal nanoparticle reveals enhanced absorption of sunlight. Photocatalysts accelerate chemical reactions by absorbing light from the sun and using the energy to drive reactions on their surfaces. They are attractive for environmentally friendly applications such as generating hydrogen from water and breaking down pollutants. Experimental studies have shown that microspheres made from metal-oxide semiconductors and embedded with metal nanoparticles are particularly effective photocatalysts, but researchers have been uncertain about why this was the case. Now, Ping Bai and his colleagues at the A*STAR Institute of High Performance Computing in Singapore have performed computer simulations that reveal what makes these structures such effective photocatalysts. Their study also provides scientists with helpful guidelines for designing plasmonic photocatalysts. Bai and his colleagues used a widely employed computational technique known as the finite element method to analyze how light interacts with a semiconductor microparticle containing a single metal nanoparticle. Their analysis revealed that the refractive index difference between the semiconductor and the catalytic medium sets up an interference pattern within the semiconductor microparticle. This interference enhances the light absorption of the embedded metal nanoparticles as a result of plasmon resonance (see image). As a consequence, the microspheres with embedded metal nanoparticles drive chemical reactions by harnessing solar energy much more efficiently than other commonly used photocatalyst structures. “The broadband absorption enhancement exists everywhere inside the microspheres,” explains Bai, “and the maximum enhancement can be hundred times greater than that of metal nanoparticles or small core–shell photocatalysts.” This explains their superior catalytic rates measured in previous experiments. In addition to explaining previous experimental findings, the analysis can also be used to inform the design of photocatalysts. In particular, it suggests that using semiconductors with higher refractive indices will maximize the broadband absorption induced by the interference, while using a mix of different plasmonic nanoparticles will enable flexible energy harvesting and enhanced selectivity. Finally, the findings also imply that locating the metal nanoparticles close to the surfaces of the microspheres will increase the catalytic rate as a consequence of the very short range of the plasmon near field. Bai and his team are now seeking to join forces with others working in the field. “Our next step is to look for end users and experimental collaborators to design, optimize and fabricate particular photocatalysts,” says Bai.
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Physics of heavy ion induced damage in nanotwinned metals revealed

A group of researchers in the Department of Mechanical Engineering and the Department of Materials Science and Engineering at Texas A&M University led by Dr. Xinghang Zhang has investigated defect dynamics in heavy ion (Krypton) irradiated nanotwinned Ag and revealed twin boundary-defect clusters interactions via in situ radiation. study on twin boundary (TB) affected zone in irradiated nanotwinned Ag High energy particles introduce severe radiation damage in metallic materials, such as Ag. This paper reports on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials. © ACS) The design of next generation nuclear reactors calls for materials with superior radiation tolerance. Under the extreme radiation conditions, a large number of defects and their clusters are generated and consequently result in mechanical instability of irradiated metallic materials. While studying radiation damage in nanotwinned Ag by in-situ irradiation technique at the IVEM facility at Argonne National Laboratory, Zhang’s students, Jin Li and Kaiyuan Yu discovered two interesting phenomena. First, they identified twin boundary affected zones wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. Additionally, in situ studies also revealed excellent resilience of twin boundaries in response to radiation: twin boundaries continue to change their geometry to facilitate the capture, transportation and removal of defect clusters. Furthermore twin boundaries can recover by absorbing opposite type of defects. “Without performing time accumulative studies, we would have missed the existence of twin boundary affected zones”, said Li. “This study provides further support for the implementation of twin boundaries as effective defect sinks for the design of radiation tolerant nanostructured metallic materials”, added Yu, who is now an assistant professor in China. The paper, "In situ Study of Defect Migration Kinetics and Self-Healing of Twin Boundaries in Heavy Ion Irradiated Nanotwinned Metals" was published in the April 2015 issue in .
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How to grow nanostructures in a controlled manner on a variety of metals

Materials scientist Irem Tanyeli from energy research institute DIFFER has discovered how you can grow nanostructures in a controlled manner on a variety of metals, by bombarding the metals with helium particles. Such controlled nanostructures provide the possibility of advanced electrodes that produce sustainable fuel using solar energy. Tanyeli and her fellow researchers from DIFFER, ITER and the University of Basel published their results in on 28 April 2015 ("Surface Modifications Induced by High Fluxes of Low Energy Helium Ions"). A nanostructured electrod A nanostructured electrode produced from widely available iron can use sunlight to cheaply produce the energy carrier hydrogen on a large scale. (Image: ICMS / DIFFER) Blowing bubbles in metal In their research Tanyeli and her colleagues exposed different metal surfaces to a hot intense beam of charged helium gas (plasma) in DIFFER's plasma experiment Magnum-PSI. Helium easily penetrates into the metal lattice where it forms bubbles that push the surrounding metal outwards. In this way different structures of tens to hundreds of nanometres in size arise per metal. By describing the differences, Tanyeli could analyse which underlying processes formed the nanostructures such as the temperature and the structure of the metal lattice. That helium plasma can cause a metal to explode in nanostructures had previously been discovered when researchers tested wall materials for fusion energy reactors. They then discovered strange shapes on the metal wall surface. In a fusion reactor these nanostructures are undesirable because they reduce the discharge of heat, but in other applications the nanostructures are very useful, thinks co-researcher and DIFFER director Richard van de Sanden. Nanostructures on aluminium Nanostructures on aluminium. Overview (a) and cross-section (b) of nanostructures on an aluminium surface. (©Tanyeli et al. / Nature Scientific Reports) Fundamental insight "Irem Tanyeli's research is important due to the fundamental insight", says Van de Sanden. "How do such nanostructures grow on a surface, which processes play a role in that, what are the bottlenecks, and how can you manage the process? If you understand that then you can produce advanced materials on a large-scale that can be given properties to order." That has a wide range of applications in sustainable energy technologies. Converting sunlight into hydrogen Tanyeli's nanostructures are interesting for catalyst applications such as the use of solar energy to produce hydrogen from water. Widely available and cheap materials can usually not compete against the efficiency of expensive but rare record holders such as platinum. But with the right nanostructures the cheaper materials can still be made competitive. That opens up possibilities for the large-scale storage and conversion of sustainable energy in the form of chemical compounds: solar fuels. Such fuels have no net CO2-emission and therefore offer opportunities for the transport sector. Solar fuels are seen as an important way of storing sustainable energy, for example the solar energy that is generated during the sun-rich summer can be stored for use during the dark winter.
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Developing portable, highly sensitive gold detection down to nanoparticles

University of Adelaide researchers are developing a portable, highly sensitive method for gold detection that would allow mineral exploration companies to test for gold on-site at the drilling rig. Using light in two different processes (fluorescence and absorption), the researchers from the University’s Institute for Photonics and Advanced Sensing (IPAS), have been able to detect gold nanoparticles at detection limits 100 times lower than achievable under current methods. Australia is the world’s second largest gold producer, worth $13 billion in export earnings. "Gold is not just used for jewellery, it is in high demand for electronics and medical applications around the world, but exploration for gold is extremely challenging with a desire to detect very low concentrations of gold in host rocks," says postdoctoral researcher Dr Agnieszka Zuber, working on the project with Associate Professor Heike Ebendorff-Heidepriem. "The presence of gold deep underground is estimated by analysis of rock particles coming out of the drilling holes. But current portable methods for detection are not sensitive enough, and the more sensitive methods require some weeks before results are available. "This easy-to-use sensor will allow fast detection right at the drill rig with the amount of gold determined within an hour, at much lower cost." The researchers have been able to detect less than 100 parts per billion of gold in water. They are now testing using samples of real rock with initial promising results. The work is funded by the Deep Exploration Technologies Cooperative Research Centre. The gold detection project is one of a series of projects which will be presented at the IPAS Minerals and Energy Sector Workshop today, aimed at linking resources specific research to local companies. Industry representatives will also hear about the Photonics Catalyst Program, a joint State Government and IPAS initiative which supports connections between advanced photonics technologies and SA industry. Manufacturing and Innovation Minister Kyam Maher says IPAS’s collaboration with partners is stimulating new technologies and contributing to the State’s reputation as a knowledge economy. "The Photonics Catalyst Program helps South Australian businesses, including resources-related companies, identify the emerging laser and sensor technologies that could transform their products or business models," Mr Maher says. "Technology plays a central role in the competitiveness of South Australian manufacturing, supporting innovation, driving product and service development and improving manufacturing performance. It will play a key role in driving change and will underpin the transformation of the South Australian economy."
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A new constitutive model for the thermo-elasto-plasticity deformation of crystals

Researchers have proposed a new thermo-elasto-plasticity constitutive model based on the interatomic potential and solid mechanics for metal crystals. Through this new model, the material behavior at different temperatures could be described accurately and conveniently. The work, led by Professor Wang TzuChiang, together with collaborators Chen Cen and Tang Qiheng at the State Key Laboratory of Nonlinear Mechanics under the CAS (Chinese Academy of Sciences) Institute of Mechanics, aims to investigate the thermo-elasto-plasticity behavior of metal crystals with a simple and efficient way. A paper describing the team's results is published in the 2015 No.5 issue of ("A new thermo-elasto-plasticity constitutive equation for crystals"). decomposition of deformation configuration Figure 1: This image shows decomposition of deformation configuration: (a) Initial configuration; (b) first intermediate configuration; (c) second intermediate configuration; (d) current configuration. © Science China Press) (click on image to enlarge) In previous researches for metal crystals, some theories based on the quantum mechanics were dependent on the vibration frequencies of lattice and their derivatives, and the calculation process was time-cosuming. On the other hand, for some forthright macroscopic models, the thermal expansion was not considered in the deformation process, and the temperature effects on plastic behavior, such as initial critical resolved shear stress and hardening modulus are difficult to determine. These problems bring inconvenience to prediction of the whole deformation behavior of metal crystals at different temperatures. Now, this new research has made an effort to solve these problems and put forward a practical method to obtain the thermo-elasto-plasticity deformation of metal crystals. In this research, the new deformation decomposition is proposed, and the total deformation contains thermal, elastic and plastic parts. The thermal strain can be obtained conveniently by the coefficient of thermal expansion from experimental data. Then, the constitutive equations are established based on the new deformation decomposition. Furthermore, the temperature effects on plastic behavior are reflected by simple expressions, which make the description of the thermo-plasticity behavior more explicitly. In this work, to reflect the effect of thermal expansion in the whole deformation process, a new deformation decomposition is given firstly, which is different with kinematical theory for the mechanics of elastic-plastic deformation for crystal. As shown in Figure 1, the deformation configuration is decomposed into four parts: the initial configuration at the undeformed state of 0 K (Figure 1(a)); the first intermediate configuration after free thermal expansions at T K (Figure 1(b)); the second intermediate configuration after elastic deformation at T K (Figure 1(c)); and the current configuration after plastic deformation at T K (Figure 1(d)). The new deformation decomposition provides a good basis to establish the constitutive equations and makes the present model applicable to structural calculation with some boundary constraints in the future. Then, the increment constitutive equations are obtained at the different deformation stages: the one is established by the rate of the second Piola-Kirchhoff stress and the rate of the Green strain, and the other one is established by the Jaumann rate of the Kirchhoff stress and symmetric parts of the velocity gradient. Meanwhile, the temperature dependences of initial critical resolved shear stress and hardening modulus are considered by exponential function. The parameters can be determined easily with three uniaxial stress-strain curves at different temperature. So the plastic behavior at different temperature can be determined accurately. Lastly, the stress-strain curves of Al crystals at different temperatures are calculated using this new model, and the calculation results are compared with experimental results. As shown in the Figure 2, the comparisons verify that the new model can predict the thermo-elasto-plasticity behavior of metal crystal very effectively. "Comparing with some widely recognized models, this new model has some characteristics as follows: firstly, the new deformation decomposition considers the thermal deformation in the whole deformation process, provides a good basis to establish the constitutive equations and makes the calculation process more simple and explicit than the MD and MC methods. Then the concise expressions for temperature effects on plastic behaviors make this new model have the ability to describe the thermo-elasto-plasticity behavior more clearly and accurately." Said the authors. This research provides an applicative method to calculate the thermo-elasto-plasticity deformation at different temperature, which is more explicit and concise than some previous models.
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When mediated by superconductivity, light pushes matter million times more

When a mirror reflects light, it experiences a slight push. This radiation pressure can be increased considerably with the help of a small superconducting island. This was revealed by the joint research done in the Aalto University and the Universities of Jyväskylä and Oulu. The finding paves a way for the studies of mechanical oscillations at the level of a single photon, the quantum of light. The results of the research were published in in April ("Cavity optomechanics mediated by a quantum two-level system"). In our everyday lives, the effects of the radiation pressure of light can be neglected. Your furniture is not moved over even though the light, or more generally the electromagnetic radiation, emitted by your lamps bounces off from its surfaces thus creating a radiation pressure force. An ordinary 100 Watt light-bulb causes a radiation pressure that is only a trillionth (one part to 1000000000000) of the normal atmospheric pressure. Nevertheless, in space the relevance of the phenomenon becomes apparent: because of the radiation pressure the tails of comets typically point away from the Sun. Radiation pressure has also been proposed as the propulsion for the solar sails. In the recent years, the radiation pressure has been harnessed also in the field of laser physics. It can be used to couple the electromagnetic laser field to, for example, the movement of the small mechanical oscillators that can be found inside ordinary watches. Due to the weakness of the interaction, one typically needs substantially strong laser fields. "Radiation pressure physics in these systems have become measurable only when the oscillator is hit by millions of photons," explains theorist Jani Tuorila from the University of Oulu. In the work reported here, the researchers combine their knowledge on experimental and theoretical physics, and show how the strength of the radiation pressure coupling can be considerably increased. They placed a superconducting island in between the electromagnetic field and the oscillator to mediate the interaction. "In the measurements, we exploited the Josephson coupling of the superconducting junctions, especially its nonlinear character," explains Juha Pirkkalainen from Aalto University, the post-doctoral researcher who conducted the measurements. The researchers were able to alter the radiation pressure coupling significantly. "With the superconducting island, the radiation pressure increased a millionfold the value we had previously achieved," reports the supervisor of the experimental group, professor Mika Sillanpää from Aalto University. Because of the increased radiation pressure coupling, the oscillator observes the electromagnetic field with the precision of a single photon. Correspondingly, the oscillators reveal themselves to the field with the resolution of a single quantum of oscillations, a phonon. "Such strong coupling allows, in principle, the measurement of quantum information from an oscillator nearly visible to the naked eye," explains professor Tero Heikkilä from the University of Jyväskylä who was in charge of the theoretical studies. The research enables the observation of quantum phenomena in larger structures than before. Thus, it allows studying the validity of the quantum mechanical laws in large structures. - Some claim that the theory holds only with very small particles. Nevertheless, the existence of an upper limit for the validity region has not been found - yet.
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Random light scattering enhances the resolution of wide-field optical microscope images

Researchers at the UT-research institute MESA+ have developed a method to improve the resolution of a conventional wide-field optical microscope. Scattered light usually reduces the resolution of conventional optical microscopes. The UT-researchers however found a simple and efficient way to actively use scattered light to improve the resolution of images. It is like the fog has cleared, according to the first author Hasan Yilmaz. The paper is published in The Optical Society’s (OSA) new high-impact journal . MOSK web MOSK web The smallest detail a traditional optical microscope can reveal is about half the wavelength of green light, or 0.25 micrometer (a micrometer is a thousandth of a millimeter). Many interesting and important structures in biological cells and computer chips have features smaller than that. A very convenient and general method to enhance the resolution of microscopes is to structure the illumination. From several pictures under different illuminations, a single high-resolution image is constructed in the computer. So far, scientists have carefully selected the clearest glass optics for such imaging. Yet, the range of materials from which clear optics can be made is limited. In many materials random scattering takes place. New method Randomly scattered laser light appears as a finely grained speckle pattern as a result of interference of many scattered light paths. Researchers at the MESA+ Institute of the University of Twente in the Netherlands have developed a new and powerful approach to use these fine speckles for high resolution imaging. Using optimized scattering materials they produce the finest-grained speckles yet made with visible light. With this speckle illumination they obtain fluorescence images that have a very high resolution (0.12 micrometer) and a wide field of view. In the new method, the object you want to see – for instance a biological cell – is placed on the substrate of the scattering material and the laser light is shone upon the scattering surface. The lens creates a speckle pattern that can be scanned on the object. Multiple low resolution images of the object are then combined in the computer, which leads to a clear image. “The resolution improvement looks like the fog has cleared” says Hasan Yilmaz, the paper’s first author. “But in fact it is the low resolution image that is taken with clear optics. The high resolution picture is taken using scattered light!” The speckle illumination method is surface-specific and robust to environmental noise. The new high-resolution imaging method, called Speckle Correlation Resolution Enhancement (SCORE) is reported in the Optical Society’s (OSA) new high-impact journal ("Speckle correlation resolution enhancement of wide-field fluorescence imaging").
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Graphene-based technique creates the smallest gaps in nanostructures

A new procedure will enable researchers to fabricate smaller, faster, and more powerful nanoscale devices - and do so with molecular control and precision. Using a single layer of carbon atoms, or graphene, nanoengineers at the University of California, San Diego have invented a new way of fabricating nanostructures that contain well-defined, atomic-sized gaps. The results from the UC San Diego Jacobs School of Engineering were published in the January issue of the journal ("Using the Thickness of Graphene to Template Lateral Subnanometer Gaps between Gold Nanostructures"). A single layer of graphene shown on a slide A single layer of graphene shown on a slide. Structures with these well-defined, atomic-sized gaps could be used to detect single molecules associated with certain diseases and might one day lead to microprocessors that are 100 times smaller than the ones in today’s computers. The ability to generate extremely small gaps - known as nanogaps - is highly desirable in fabricating nanoscale structures, which are typically used as components in optic and electronic devices. By decreasing the spacing between electronic circuits on a microchip, for example, one can fit more circuits on the same chip to produce a device with greater computing power. A team of Ph.D. students and undergraduate researchers led by UC San Diego nanoengineering professor Darren Lipomi demonstrated that the key to generating a smaller nanogap between two nanostructures involves using a graphene spacer, which can be etched away to create the gap. Graphene is the thinnest material known: it is simply a single layer of carbon atoms and measures approximately 0.3 nanometers (nm), which is about 100,000 times thinner than a human hair. The technique developed by Lipomi’s team overcomes some of the limitations of standard fabrication methods, such as photolithography and electron-beam lithography. By comparison, the smallest nanogaps that can be generated using the standard methods are 10–20 nm wide. “Making a nanogap is interesting from a philosophical standpoint,” said Lipomi. “While most efforts in nanotechnology focus on making materials, we’ve essentially made nothing - but with controlled dimensions.” Making “nothing” The method for making nanogaps begins with the production of thin films in which a single layer of graphene is sandwiched between two gold metal sheets. First, graphene is grown on a copper substrate, and then layered on top with a sheet of gold metal. Because graphene sticks better to gold than to copper, the entire graphene single-layer can be easily removed and remains intact over large areas. Compared to other techniques that are used to produce similar layered structures, this method allows graphene to be transferred to gold film with minimal defects or contamination. “This new method, which we developed in our lab, is called metal-assisted exfoliation. This is the only way so far in which we can place single-layer graphene between two metals and ensure that it contains no rips, cracks, folds, or unwanted chemical species,” said Alex Zaretski, a graduate student in Lipomi’s research group who pioneered the technique and is the first author of the study. “Metal-assisted exfoliation can potentially be useful for industries that use large areas of graphene.” Once the gold/graphene composite is separated from the copper substrate, the newly exposed side of the graphene layer is sandwiched with another gold sheet to produce the gold:single-layer graphene:gold thin film. The films are then sliced into 150 nm-wide nanostructures. Finally, the structures are treated with oxygen plasma to remove graphene. Scanning electron micrographs of the structures reveal extremely small nanogaps between the gold layers. Nanogap applications One potential application for this technology is in ultra-sensitive detection of single molecules, particularly those that are characteristic of certain diseases. When light is shined upon structures with extremely small gaps, the electromagnetic field that is confined within the gap becomes enormously enhanced. This enhanced electromagnetic field, in turn, increases the signal produced by any molecule within the gap. “If some disease marker comes in and bridges the gap between the nanostructures, you would observe a change in the light scattering from the nanogap that would correspond to whether the disease was present or not,” said Lipomi. While the technique reported in this study can produce nanostructures suitable for optical applications, it exhibits a major drawback for electronic applications. Raman spectroscopic measurements of the gold nanostructures reveal that small amounts of graphene still remain between the gold layers after being treated with oxygen plasma. This means that only the graphene exposed near the surfaces of the gold nanostructures can be removed so far. Having graphene still in the structures is not desirable for electronic devices, which require an entire gap between the structures. The team is working to figure out how to solve this problem. In the future, the team would also like to explore ways to vary the thickness of the well-defined gap between the structures by increasing the number of graphene layers. “For optical applications, it would be desirable to have gaps that are a little bit bigger than what we’ve generated. We just wanted to show, in principle, the smallest gap size that is possible to achieve,” said Lipomi.
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Researchers model new atomic structures of gold nanoparticle

They may deal in gold, atomic staples and electron volts rather than cement, support beams and kilowatt-hours, but chemists have drafted new nanoscale blueprints for low-energy structures capable of housing pharmaceuticals and oxygen atoms. Led by UNL's Xiao Cheng Zeng and former visiting professor Yi Gao, new research has revealed four atomic arrangements of a gold nanoparticle cluster. The arrangements exhibit much lower potential energy and greater stability than a standard-setting configuration reported last year by a Nobel Prize-winning team from Stanford University. The modeling of these arrangements could inform the cluster's use as a transporter of pharmaceutical drugs and as a catalyst for removing pollutants from vehicular emissions or other industrial byproducts, Zeng said. atomic arrangements of a gold nanocluster This rendering shows the atomic arrangements of a gold nanocluster as reported in a new study led by UNL chemist Xiao Cheng Zeng. The cluster measures about 1.7 nanometers long - roughly the same length that a human fingernail grows in two seconds. Zeng and his colleagues unveiled the arrangements for a molecule featuring 68 gold atoms and 32 pairs of bonded sulfur-hydrogen atoms. Sixteen of the gold atoms form the molecule's core; the remainder bond with the sulfur and hydrogen to form a protective coating that stems from the core. Differences in atomic arrangements can alter molecular energy and stability, with less potential energy making for a more stable molecule. The team calculates that one of the arrangements may represent the most stable possible structure in a molecule with its composition. "Our group has helped lead the front on nano-gold research over the past 10 years," said Zeng, an Ameritas University Professor of chemistry. "We've now found new coating structures of much lower energy, meaning they are closer to the reality than (previous) analyses. So the deciphering of this coating structure is major progress." The researchers reported their findings in the April 24 edition of ("Unraveling structures of protection ligands on gold nanoparticle Au68(SH)32"), an online journal from the American Association for the Advancement of Science. The structure of the molecule's gold core was previously detailed by the Stanford team. Building on this, Zeng and his colleagues used a computational framework dubbed "divide-and-protect" to configure potential arrangements of the remaining gold atoms and sulfur-hydrogen pairs surrounding the core. The researchers already knew that the atomic coating features staple-shaped linkages of various lengths. They also knew the potential atomic composition of each short, medium and long staple -- such as the fact that a short staple consists of two sulfur atoms bonded with one gold. By combining this information with their knowledge of how many atoms reside outside the core, the team reduced the number of potential arrangements from millions to mere hundreds. "We divided 32 into the short, middle and long (permutations)," said Zeng, who helped develop the divide-and-protect approach in 2008. "We lined up all those possible arrangements, and then we computed their energies to find the most stable ones. "Without those rules, it's like finding a needle in the Platte River. With them, it's like finding a needle in the fountain outside the Nebraska Union. It's still hard, but it's much more manageable. You have a much narrower range." The researchers resorted to the computational approach because of the difficulty of capturing the structure via X-ray crystallography or single-particle transmission electron microscopy, two of the most common imaging methods at the atomic scale. Knowing the nanoparticle's most stable configurations, Zeng said, could allow biomedical engineers to identify appropriate binding sites for drugs used to treat cancer and other diseases. The findings could also optimize the use of gold nanoparticles in catalyzing the oxidation process that transforms dangerous carbon monoxide emissions into the less noxious carbon dioxide, he said.
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Study explores the interaction of carbon nanotubes and the blood-brain barrier

A research published in ("The interaction of carbon nanotubes with an in vitro blood-brain barrier model and mouse brain in vivo") studies the interaction of carbon nanotubes and the blood-brain barrier through two different proceedings. The study was carried by the Institute of Pharmaceutical Science at the King's College London and Elzbieta Pach and Belén Ballesteros, members of the ICN2 Electron Microscopy Division, participated on the electron microscopy characterization studies. translocation of carbon nanotubes cross porcine brain endothelial cells membrane Translocation of “individual” MWNTs-NH3+ across porcine brain endothelial cells membrane. Images acquired using the STEM detection system on the Magellan HRSEM at 20 kV. The study investigates the ability of amino-functionalized multi-walled carbon nanotubes (MWNTs-NH3+) to cross the Blood-Brain Barrier (BBB) by two ways: in vitro using a co-culture BBB model comprising primary porcine brain endothelial cells (PBEC) and primary rat astrocytes and, in vivo, following a systemic administration of radiolabelled f-MWNTs. The study carried out at ICN2 has allowed the corroboration of the results and the better understanding of the processes. Images by Transmission Electron microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) showed that the cells or the tight junction assemblies were not damaged, that the interaction of MWNTs-NH3+ and the plasma membrane of the endothelial cells took place after 4 h of incubation and confirmed that MWNTs-NH3+ crossed the PBEC monolayer via energy-dependent transcytosis. Also, high resolution TEM (HRTEM) and Electron Energy Loss Spectroscopy (EELS) showed that the graphitic structure of the MWNTs-NH3+ was preserved following uptake into PBEC. To sum up, researchers were able to demonstrate, for the first time, the ability of MWNTs-NH3+ to cross the BBB in vitro with low voltage STEM imaging, thus providing solid evidence using electron microscopy for each step of the transcytosis process. This research also stands out because its results could lead to the use of CNTs in new applications. For instance, they could work as nanocarriers for delivery of drugs and biologics to the brain, after systemic administration.
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Simpler nanoscale bioreplication of beetle decoys

Ash trees in 22 eastern states of U.S.A. are being decimated by emerald ash borers (EABs), an Asian beetle that arrived in Michigan more than two decades ago. The pest has even spread westwards into Kansas and Colorado. Nothing seemed to be effective against EABs, until decoys designed to mimic female EABs were found in 2012 by a group of researchers at the Pennsylvania State University to be successful in enticing male EABs for mating. Last year, the same researchers found the decoys could be used to electrocute and kill the seduced males. The iridescent green beetles are not vectors of any disease. Rather, their larvae bore tunnels in the trunks of the ash trees to feed on the sap, thereby starving the trees. Also, the numerous tunnels seriously weaken the trunks. The electrocuting decoys could assist forestry managers in slowing the spread of the pest species. Industrial-scale production of these decoys would be necessary for success. Penn State engineers led by Akhlesh Lakhtakia, Charles Godfrey Binder professor of engineering science and mechanics, had devised a nanofabrication technique to coat the upper parts of a dead female EAB with a dense assembly of 500-nm tall nanocylinders made of nickel. Having the same shape as the beetle, the coat is strengthened by an electrochemical process into a negative die. A matching positive die of epoxy is then made from the negative die. Numerous decoys can be made by hot stamping a specially prepared sheet of a common polymer between the pair of matching dies. The bioreplicated decoys are painted metallic green. Their success in luring male beetles is due to the replication of surface texture of the female beetle with very high resolution. Although this technique was devised for mass production of decoys, improvements are needed for even faster production. Tarun Gupta, a professor of industrial engineering at the Western Michigan University, visited Penn State for a sabbatical semester to work with Lakhtakia on making the negative nickel die not from just a single female EAB, but from an array of several female EABs instead. The production capacity was enhanced tenfold in Lakhtakia’s laboratory and can be scaled up hundredfold or more in factories. The researchers also eliminated the positive die, deciding to fill up the multiple cavities of the negative die with a liquid polymer that is thermally curable. Stephen Swiontek, a doctoral student working under Lakhtakia’s supervision, optimized the thermal curing step. Multiple decoys made simultaneously were painted metallic green. “The new bioreplication technique is much simpler than the predecessor technique,” said Lakhtakia, “because a large number of decoys can be simultaneously made. Moreover, positive dies need not be fabricated at all.” The researchers have published their work in the April 2015 issue of the ("Simpler Mass Production of Polymeric Visual Decoys for the Male Emerald Ash Borer (AgriAgrilus planipennis)"). Lakhtakia is confident that the new bioreplication technique is ready to combat the spread of many other insect pests in the same family as the EAB.
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Graphene brings 3-D holograms clearer and closer

From mobile phones and computers to television, cinema and wearable devices, the display of full colour, wide-angle, 3D holographic images is moving ever closer to fruition, thanks to international research featuring Griffith University ("Athermally photoreduced graphene oxides for three-dimensional holographic images"). Led by Melbourne's Swinburne University of Technology and including Dr Qin Li, from the Queensland Micro- and Nanotechnology Centre within Griffith's School of Engineering, scientists have capitalised on the exceptional properties of graphene and are confident of applications in fields such as optical data storage, information processing and imaging. "While there is still work to be done, the prospect is of 3D images seemingly leaping out of the screens, thus promising a total immersion of real and virtual worlds without the need for cumbersome accessories such as 3D glasses," says Dr Li. First isolated in the laboratory about a decade ago, graphene is pure carbon and one of the thinnest, lightest and strongest materials known to humankind. A supreme conductor of electricity and heat, much has been written about its mechanical, electronic, thermal and optical properties. "Graphene offers unprecedented prospects for developing flat displaying systems based on the intensity imitation within screens," says Dr Li, who conducted carbon structure analysis for the research. "Our consortium, which also includes China's Beijing Institute of Technology and Tsinghua University, has shown that patterns of photo-reduced graphene oxide (rGO) that are directly written by laser beam can produce wide-angle and full-colour 3D images. "This was achieved through the discovery that a single femtosecond (fs) laser pulse can reduce graphene oxide to rGO with a sub-wavelength-scale feature size and significantly differed refractive index. "Furthermore, the spectrally flat optical index modulation in rGOs enables wavelength-multiplexed holograms for full colour images." Researchers say the sub-wavelength feature is particularly important because it allows for static holographic 3D images with a wide viewing angle up to 52 degrees. Such laser-direct writing of sub-wavelength rGO featured in dots and lines could revolutionise capabilities across a range of optical and electronic devices, formats and industry sectors. "The generation of multi-level modulations in the refractive index of GOs, and which do not require any solvents or post-processing, holds the potential for in-situ fabrication of rGO-based electro-optic devices," says Dr Li. "The use of graphene also relieves pressure on the world's dwindling supplies of indium, the metallic element that has been commonly used for electronic devices. "Other technologies are being developed in this area, but rGO looks by far the most promising and most practical, particularly for wearable devices. The prospects are quite thrilling."
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Chemists' synthesis of silicon oxides opens 'new world in a grain of sand'

Gregory H. Robinson, University of Georgia
Gregory H. Robinson is the University of Georgia Foundation Distinguished Professor of Chemistry.
The study, published April 20 in the journal ("Stabilization of elusive silicon oxides"), gives details on the first time chemists have been able to trap molecular species of silicon oxides.

Using a technique they developed in 2008, the UGA team succeeded in isolating silicon oxide fragments for the first time, at room temperature, by trapping them between stabilizing organic bases.

"In the 2008 discovery, we were able to stabilize the disilicon molecule, which previously could only be studied at extremely low temperatures on a solid argon matrix," said Gregory H. Robinson, UGA Foundation Distinguished Professor of Chemistry and the study's co-author. "We demonstrated that these organic bases could stabilize a variety of extremely reactive molecules at room temperature."

The columns, or groups, of elements of the periodic table generally share similar chemical properties. Group 14, for example, contains the element carbon, as well as silicon, the most carbon-like of all the elements. However, there are significant differences between the two. While the oxides of carbon, carbon dioxide and carbon monoxide are widely known, the molecular chemistry of corresponding silicon oxides is essentially unknown, due to the great reactivity of silicon-oxygen multiple bonds.

Silicon monoxide, on the other hand, has been described as the most abundant silicon oxide in the universe but, terrestrially it is only persistent at high temperatures, about 1,200 degrees Celsius. Naturally abundant silica ((SiO2)n) exists on Earth as sand--a network solid wherein each silicon atom bonds to four oxygen atoms in a process that repeats infinitely.
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A light switch for superconductivity

A device that can be switched between insulating and superconducting states by irradiation with light has been developed by researchers from RIKEN and the Institute for Molecular Science (, "Light-induced superconductivity using a photoactive electric double layer"). The development could ultimately lead to more efficient superconducting microelectronics. Mott insulator and superconductor Irradiating a thin crystal of κ-Br on a monolayer of spiropyran molecules with visible (left) and ultraviolet (right) light switches the κ-Br material between insulating and superconducting states due to the formation of an electric double layer. (© AAAS) The properties of solid materials can be dramatically altered by applying an electric field. In a common electronic component called a field-effect transistor, the flow of electrons through a semiconducting channel is controlled according to the strength of an internal electric field, which is created by applying a voltage to an insulating material—a dielectric. Higher field strengths provide more efficient conduction, but at very high fields the dielectric material begins to break down and conduct itself. To overcome this limitation, scientists have turned to the use of ionic liquids. When a voltage is applied to an ionic liquid, the charged particles in the liquid move to the surface of the channel material, creating an ‘electric double layer’ (EDL) that is not susceptible to dielectric breakdown. The high electric fields enabled by this technique have previously allowed researchers to convert the channel material from an insulator into a superconductor. So far, switching of the electric field has only been possible at relatively high temperatures because the ionic motion freezes at approximately 200 kelvin. Masayuki Suda and Hiroshi Yamamoto from the IMS and RIKEN, in collaboration with RIKEN’s Reizo Kato, have now shown that a light-sensitive molecule can be used to switch on a superconducting state at temperatures as low as 5 kelvin. The team replaced the ionic liquid with a single layer of spiropyran molecules, which are ionic under ultraviolet light and non-ionic under visible light. To test this strategy, they placed an organic crystal called ?-Br, which is known to have a superconducting state, on a single layer of self-assembled spiropyran molecules mounted on a thin oxide film. They confirmed that the resistance of the ?-Br switched from a high-resistance state under visible light to a low-resistance state when illuminated with ultraviolet light, due to the formation of an EDL (Fig. 1). “Even at low temperatures, ultraviolet light induces a zwitterionic structure in spiropyran molecules and a situation very similar to an EDL without an applied voltage, leading to superconductivity,” says Suda. “In this system, light induces the superconducting state by photoisomerization of the spiropyran molecules,” says Suda. “If we could get light to generate the superconducting carriers directly, other types of light-driven devices could also be possible.”
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Ultra-sensitive sensor detects individual electrons

A Spanish-led team of European researchers at the University of Cambridge has created an electronic device so accurate that it can detect the charge of a single electron in less than one microsecond. It has been dubbed the 'gate sensor' and could be applied in quantum computers of the future to read information stored in the charge or spin of a single electron ("Probing the limits of gate-based charge sensing"). Silicon chip Silicon chip used for the design of the gate sensor. (Image: TOLOP) In the same Cambridge laboratory in the United Kingdom where the British physicist J.J. Thomson discovered the electron in 1897, European scientists have just developed a new ultra-sensitive electrical-charge sensor capable of detecting the movement of individual electrons. "The device is much more compact and accurate than previous versions and can detect the electrical charge of a single electron in less than one microsecond," says M. Fernando González Zalba, leader of this research from the Hitachi Cambridge Laboratory and the Cavendish Laboratory. Details of the breakthrough have been published in the journal 'Nature Communications' and its authors predict that these types of sensors, dubbed 'gate sensors', will be used in quantum computers of the future to read information stored in the charge or spin of a single electron. "We have called it a gate sensor because, as well as detecting the movement of individual electrons, the device is able to control its flow as if it were an electronic gate which opens and closes," explains González Zalba. The researchers have demonstrated the possibility of detecting the charge of an electron with their device in approximately one nanosecond, the best value obtained to date for this type of system. This has been achieved by coupling a gate sensor to a silicon nanotransistor where the electrons flow individually. In general, the electrical current which powers our telephones, fridges and other electrical equipment is made up of electrons: minuscule particles carrying an electrical charge travelling in their trillions and whose collective movement makes these appliances work. However, this is not the case of the latest cutting-edge devices such as ultra-precise biosensors, single electron transistors, molecular circuits and quantum computers. These represent a new technological sector which bases its electronic functionality on the charge of a single electron, a field in which the new gate sensor can offer its advantages.
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Scientists use nanoscale building blocks and DNA 'glue' to shape 3D superlattices

Taking child's play with building blocks to a whole new level—the nanometer scale—scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory have constructed 3D "superlattice" multicomponent nanoparticle arrays where the arrangement of particles is driven by the shape of the tiny building blocks. The method uses linker molecules made of complementary strands of DNA to overcome the blocks' tendency to pack together in a way that would separate differently shaped components. The results, published in ("Superlattices Assembled through Shape-Induced Directional Binding"), are an important step on the path toward designing predictable composite materials for applications in catalysis, other energy technologies, and medicine. self-assembly of nanoparticles into superlattices Controlling the self-assembly of nanoparticles into superlattices is an important approach to build functional materials. The Brookhaven team used nanosized building blocks—cubes or octahedrons—decorated with DNA tethers to coordinate the assembly of spherical nanoparticles coated with complementary DNA strands. (click on image to enlarge) "If we want to take advantage of the promising properties of nanoparticles, we need to be able to reliably incorporate them into larger-scale composite materials for real-world applications," explained Brookhaven physicist Oleg Gang, who led the research at Brookhaven's Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility. "Our work describes a new way to fabricate structured composite materials using directional bindings of shaped particles for predictable assembly," said Fang Lu, the lead author of the publication. The research builds on the team's experience linking nanoparticles together using strands of synthetic DNA. Like the molecule that carries the genetic code of living things, these synthetic strands have complementary bases known by the genetic code letters G, C, T, and A, which bind to one another in only one way (G to C; T to A). Gang has previously used complementary DNA tethers attached to nanoparticles to guide the assembly of a range of arrays and structures. The new work explores particle shape as a means of controlling the directionality of these interactions to achieve long-range order in large-scale assemblies and clusters. Spherical particles, Gang explained, normally pack together to minimize free volume. DNA linkers—using complementary strands to attract particles, or non-complementary strands to keep particles apart—can alter that packing to some degree to achieve different arrangements. For example, scientists have experimented with placing complementary linker strands in strategic locations on the spheres to get the particles to line up and bind in a particular way. But it's not so easy to make nanospheres with precisely placed linker strands. "We explored an alternate idea: the introduction of shaped nanoscale 'blocks' decorated with DNA tethers on each facet to control the directional binding of spheres with complementary DNA tethers," Gang said. When the scientists mixed nanocubes coated with DNA tethers on all six sides with nanospheres of approximately the same size, which had been coated with complementary tethers, these two differently shaped particles did not segregate as would have been expected based on their normal packing behavior. Instead, the DNA "glue" prevented the separation by providing an attractive force between the flat facets of the blocks and the tethers on the spheres, as well as a repulsive force between the non-pairing tethers on same-shaped objects.  DNA tethers lead cubic blocks and spheres to self assemble The DNA tethers lead cubic blocks and spheres to self assemble so that one sphere binds to each face of a cube, resulting in a regular, repeating arrangement. "The DNA permits us to enforce rules: spheres attract cubes (mutually); spheres do not attract spheres; and cubes do not attract cubes," Gang said. "This breaks the conventional packing tendency and allows for the system to self-assemble into an alternating array of cubes and spheres, where each cube is surrounded by six spheres (one to a face) and each sphere is surrounded by six cubes." Using octahedral blocks instead of cubes achieved a different arrangement, with one sphere binding to each of the blocks' eight triangular facets. The method required some thermal processing to achieve the most uniform long-range order. And experiments with different types of DNA tethers showed that having flexible DNA strands was essential to accommodate the pairing of differently shaped particles. "The flexible DNA shells 'soften' the particles, which allows them to fit into arrangements where the shapes do not match geometrically," Lu said. But excessive softness results in unnecessary particle freedom, which can ruin a perfect lattice, she added. Finding the ideal flexibility for the tethers was an essential part of the work. 3D arrangement of cubes and octahedrons Changing the shape of the blocks from cubes to octahedrons results in a different 3-D arrangement. The scientists used transmission and scanning electron microscopy at the CFN and also conducted x-ray scattering experiments at the National Synchrotron Light Source, another DOE Office of Science User Facility at Brookhaven Lab, to reveal the structure and take images of assembled clusters and lattices at various length scales. They also explained the experimental results with models based on the estimation of nanoscale interactions between the tiny building blocks. "Ultimately, this work shows that large-scale binary lattices can be formed in a predictable manner using this approach," Gang said. "Given that our approach does not depend on the particular particle's material and the large variety of particle shapes available—many more than in a child's building block play set—we have the potential to create many diverse types of new nanomaterials."
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Mechanical cloaks of invisibility - without complicated mathematics

A honeycomb is a very stable structure. If it has a larger hole, however, stability is largely lost. What might a honeycomb look like, which survives external forces in spite of a hole? Such stable types of known constructions might be useful in architecture or when developing new construction materials. So far, the mathematical expenditure required has been very high and did not lead to the success desired in mechanics. Researchers of Karlsruhe Institute of Technology (KIT) have now found a new principle that considerably facilitates the mathematical approach and produces promising results with simple means. Mechanical cloak of invisibility Mechanical cloak of invisibility: In a regular honeycomb structure (left), a hole is compensated by a distortion (right). External forces act as if the hole would not exist. (Image: T. Bückmann/KIT) The conception of “coordinate transformation” may sound complex, but such mathematical transformations are rather helpful: A mesh of connected points is drawn onto a rubber skin. Coordinate transformation is simulated by extending and distorting this rubber surface. When the assumed mesh can be mapped onto material distribution, a rather universal design approach results. It can be used to direct e.g. mechanical forces acting on the material along the tracks desired. For light, such transformations are based on the mathematics of transformation optics. So far, however, it has been impossible to transfer this principle to real materials and components in mechanics. The mathematics made impossible requirements on the material. To overcome these difficulties, researchers of the KIT Institute of Applied Physics around first author Tiemo Bückmann found a new, simple method. “We imagined a network of electric resistors,” Bückmann explains. “The wire connections between the resistors may be chosen to be of variable length, but their value does not change. Electric conductivity of the network even remains unchanged, when it is deformed.” The researchers transferred this thought experiment to practice. “In mechanics, this principle is found again when imagining small springs instead of resistors,” Tiemo Bückmann says. “We can make single springs longer or shorter when adapting their shapes, such that the forces between them remain the same. This simple principle saves computation expenditure and allows for the direct transformation of real materials.” Analysis of a hole in a hexagonal structure Analysis of a hole in a hexagonal structure: External forces strongly deform the structure, the structure is unstable. By means of the new construction method, this error can be reduced strongly. (Image: T. Bückmann) (click on image to enlarge) The researchers tested their method in a model experiment with a material made of printed polymer. A stable hexagonal honeycomb structure was provided with a hole. Due to its reduced stability, the distorting forces first caused an error of more than 700 percent. After application of the newly developed transformation, the error amounted to 26 percent only. The results have just been published in the ("Mechanical cloak design by direct lattice transformation"). Applications are manifold, as the new method can be used to calculate known composite materials or mechanical support constructions. Even special designs will react as stably as possible to external forces – as if the support construction would not have been deformed.
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Low-reflection, nanostructured wings make butterflies nearly invisible

Researchers of KIT under the direction of Hendrik Hölscher found that irregular nanostructures on the surface of the butterfly wing cause the low reflection. In theoretical experiments, they succeeded in reproducing the effect that opens up fascinating application options, e.g. for displays of mobile phones or laptops. The results are published in the current issue of (DOI: 10.1038/ncomms7909). Lund Irregularity of the size and distribution of nanostructures on the surface of the butterfly wing causes low reflection of light at all view angles. (Photo: Radwanul Hasan Siddique, KIT) Transparent materials such as glass, always reflect part of the incident light. Some animals with transparent surfaces, such as the moth with its eyes, succeed in keeping the reflections small, but only when the view angle is vertical to the surface. The wings of the glasswing butterfly that lives mainly in Central America, however, also have a very low reflection when looking onto them under higher angles. Depending on the view angle, specular reflection varies between two and five percent. For comparison: As a function of the view angle, a flat glass plane reflects between eight and 100 percent, i.e. reflection exceeds that of the butterfly wing by several factors. Interestingly, the butterfly wing does not only exhibit a low reflection of the light spectrum visible to humans, but also suppresses the infrared and ultraviolet radiation that can be perceived by animals. This is important to the survival of the butterfly. For research into this so far unstudied phenomenon, the scientists examined glasswings by scanning electron microscopy. Earlier studies revealed that regular pillar-like nanostructures are responsible for the low reflections of other animals. The scientists now also found nanopillars on the butterfly wings. In contrast to previous findings, however, they are arranged irregularly and feature a random height. Typical height of the pillars varies between 400 and 600 nanometers, the distance of the pillars ranges between 100 and 140 nanometers. This corresponds to about one thousandth of a human hair. In simulations, the researchers mathematically modeled this irregularity of the nanopillars in height and arrangement. They found that the calculated reflected amount of light exactly corresponds to the observed amount at variable view angles. In this way, they proved that the low reflection at variable view angles is caused by this irregularity of the nanopillars. Hölscher’s doctoral student Radwanul Hasan Siddique, who discovered this effect, considers the glasswing butterfly a fascinating animal: “Not only optically with its transparent wings, but also scientifically. In contrast to other natural phenomena, where regularity is of top priority, the glasswing butterfly uses an apparent chaos to reach effects that are also fascinating for us humans.” The findings open up a range of applications wherever low-reflection surfaces are needed, for lenses or displays of mobile phones, for instance. Apart from theoretical studies of the phenomenon, the infrastructure of the Institute of Microstructure Technology also allows for practical implementation. First application tests are in the conception phase at the moment. Prototype experiments, however, already revealed that this type of surface coating also has a water-repellent and self-cleaning effect.
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Surface matters: Huge reduction of heat conduction observed in flat silicon channels

Combining state-of-the-art realistic atomistic modelling and experiments, the paper describes how thermal conductivity of ultrathin silicon membranes is controlled to large extent by the structure and the chemical composition of their surface. A detailed understanding of the connections of fabrication and processing to structural and thermal properties of low-dimensional nanostructures is essential to design materials and devices for phononics, nanoscale thermal management, and thermoelectric applications. The ability of materials to conduct heat is a concept that we are all familiar with from everyday life. The modern story of thermal transport dates back to 1822 when the brilliant French physicist Jean-Baptiste Joseph Fourier published his book “Théorie analytique de la chaleur” (The Analytic Theory of Heat), which became a corner stone of heat transport. He pointed out that the thermal conductivity, i.e., ratio of the heat flux to the temperature gradient is an intrinsic property of the material itself. different surfaces of the Si membranes The different circles represent the studied surfaces of the Si membranes: crystalline, rough, flat with native SiO2, and rough with native SiO2. The right image shows a representative thermal map on the membranes upon a localized thermal excitation used to measure the thermal conductivity. The advent of nanotechnology, where the rules of classical physics gradually fail as the dimensions shrink, is challenging Fourier's theory of heat in several ways. A paper published in ("Tuning Thermal Transport in Ultrathin Silicon Membranes by Surface Nanoscale Engineering") and led by researchers from the Max Planck Institute for Polymer Research (Germany), the Catalan Institute of Nanoscience and Nanotechnology (ICN2) at the campus of the Universitat Autònoma de Barcelona (UAB) (Spain) and the VTT Technical Research Centre of Finland (Finland) describes how the nanometre-scale topology and the chemical composition of the surface control the thermal conductivity of ultrathin silicon membranes. The work was funded by the European Project Membrane-based phonon engineering for energy harvesting (MERGING). The results show that the thermal conductivity of silicon membranes thinner than 10 nm is 25 times lower than that of bulk crystalline silicon and is controlled to a large extent by the structure and the chemical composition of their surface. Combining state-of-the-art realistic atomistic modelling, sophisticated fabrication techniques, new measurement approaches and state-of-the-art parameter-free modelling, researchers unravelled the role of surface oxidation in determining the scattering of quantized lattice vibrations (phonons), which are the main heat carriers in silicon. Both experiments and modelling showed that removing the native oxide improves the thermal conductivity of silicon nanostructures by almost a factor of two, while successive partial re-oxidation lowers it again. Large-scale molecular dynamics simulations with up to 1,000,000 atoms allowed the researchers to quantify the relative contributions to the reduction of the thermal conductivity arising from the presence of native SiO2 and from the dimensionality reduction evaluated for a model with perfectly specular surfaces. Silicon is the material of choice for almost all electronic-related applications, where characteristic dimensions below 10 nm have been reached, e.g. in FinFET transistors, and heat dissipation control becomes essential for their optimum performance. While the lowering of thermal conductivity induced by oxide layers is detrimental to heat spread in nanoelectronic devices, it will turn useful for thermoelectric energy harvesting, where efficiency relies on avoiding heat exchange across the active part of the device. The chemical nature of surfaces, therefore, emerges as a new key parameter for improving the performance of Si-based electronic and thermoelectric nanodevices, as well as of that of nanomechanical resonators (NEMS). This work opens new possibilities for novel thermal experiments and designs directed to manipulate heat at such scales.
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Nanoscientists model atomic structures of three bacterial nanomachines

esearchers at UCLA’s California NanoSystems Institute have become the first to produce images of the atomic structures of three specific biological nanomachines, each derived from a different potentially deadly bacterium — an achievement they hope will lead to antibiotics targeted toward specific pathogens. The scientists used a leading-edge technology called cryo electron microscopy, or cryoEM, to reveal the form and function of these important structures. Papers on their findings were published in three top-tier journals: , , and . Two of the nanomachines are structures called contractile ejection systems, which their bacteria use to transfer toxic molecules into healthy cells to usurp them for their own purposes, to attack rival bacteria by delivering toxins into them, and other functions. These structures have sheath–tube assemblies that create openings in the outer membranes of target cells through which they can insert toxic molecules. The third nanomachine — different from the other two — is a pore structure that delivers deadly anthrax toxin into mammalian cells, once the anthrax bacteria is in the bloodstream. This mechanism is how anthrax bacteria activate the disease in an infected animal or person. How the nanomachines work had been poorly understood, but the UCLA researchers used a cryoEM equipped with a special camera called a direct electron detector to produce highly detailed images. The scientists hope the new information about how they function will enable them to create antibiotics that target bacterial pathogens. The team, led by Hong Zhou, professor of microbiology, immunology and molecular genetics, and of chemistry and biochemistry, runs the Electron Imaging Center for Nanomachines laboratory, which is based at CNSI and houses UCLA’s Titan Krios electron microscope — a highly sophisticated and rare cryoEM. “As the centerpiece of our electron microscopy core lab, the cryo electron microscope is enabling exploration of new territory in molecular biology,” said Jeff Miller, director of the California NanoSystems Institute. “These unprecedented images enable us to understand the actual workings of these remarkable structures.” Anthrax toxin In a paper published online by ("Atomic structure of anthrax protective antigen pore elucidates toxin translocation"), Professor Zhou and his team reported that they were the first to determine the atomic structure of the anthrax toxin pore, the major disease molecule of Bacillus anthracis, the bacterium that causes the disease anthrax in humans and animals. The anthrax toxin pore’s atomic structure is mushroom-shaped with a gate inside the “shaft.”

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The finding confirms how the disease affects cells. When healthy cells encounter nanoscale objects in the body, they assume the objects are nutrients and absorb them. Like a Trojan horse, the toxin pore appears to the cells as something beneficial — in this case, a nutrient — and is taken in by the cell. But once inside the cell, the pore senses the change to a more acidic environment, which opens the pore’s gate and releases the anthrax toxin molecule into the cell. “This is a very important step toward understanding this mechanism, and it is essential for any anthrax countermeasure,” Zhou said. “It also informs our understanding of the mechanisms of other toxins that function like anthrax, which could lead to other targeted antibiotic drugs.” Tularemia type VI secretion system Another nanomachine was described by Dr. Marcus Horwitz, a UCLA professor of medicine and of microbiology, immunology and molecular genetics, who worked with Zhou’s team. In a study published in the journal ("Atomic Structure of T6SS Reveals Interlaced Array Essential to Function"), the scientists reported the first atomic resolution model of any type VI secretion system, or T6SS, a nanomachine found in roughly 25 percent of gram-negative bacteria. Gram-negative bacteria are responsible for diseases such as cholera, salmonellosis, Legionnaires’ disease and melioidosis, and severe infections including gastroenteritis, pneumonia and meningitis. For the new study, the scientists examined Francisella tularensis, a bacterium that causes tularemia and is of great concern as a potential bioterrorism agent. Built from component proteins, the T6SS nanomachine has an atomic structure that resembles a piston. When F. tularensis is taken up into a type of white blood cell called a macrophage it is surrounded by a bubble-like membrane, a structure known as a phagosome. The T6SS nanomachine then assembles inside the bacterium, where it plunges a tube through the bacterial wall and the membrane of the phagosome into the cytoplasm, the substance inside the macrophage. This enables the bacterium to escape the phagosome into the cytoplasm, where it can complete its lifecycle and multiply. Soon, the macrophage fills with bacteria and ruptures, freeing the bacteria to infect other cells. Thus, the T6SS is a novel target for antibiotics against this bacterium, and against others that use it to survive within host cells or to combat rival bacteria. “We are already identifying drug molecules that target the F. tularensis T6SS,” Horwitz said. “Knowing how this structure works guides us in selecting drug molecules that block its assembly or function. The overall goal is to find new antibiotics that directly target this top-tier bioterrorism agent and other gram-negative bacteria with a T6SS such as Vibrio cholerae, Pseudomonas aeruginosa, Burkholderia pseudomallei, and pathogenic Escherichia coli.” Horwitz and his team could potentially also develop wider-spectrum drugs that work on many different gram-negative pathogens that have in common a T6SS. Pseudomonas aeruginosa In humans and animals, a bacterium called Pseudomonas aeruginosa causes infectious diseases that lead to generalized inflammation and sepsis, a dangerous infection of the blood. A team led by Zhou and Miller discovered the atomic structures of R-type pyocins, contractile ejection systems of Pseudomonas aeruginosa. Their findings were published online by ("Atomic structures of a bactericidal contractile nanotube in its pre- and postcontraction states"). R-type pyocins are used by the bacterium to rapidly insert their nanotubes, like battering rams, into the cell membranes of competing bacteria to kill the competitors, giving Pseudomonas aeruginosa easier access to nutrients. These pyocins appear to create a channel in the outer envelope of the target bacteria, which essentially acts to weaken and kill it. This ability has made R-type pyocins the focus of research into possible antimicrobial and bioengineering applications, and scientists believe they could be engineered to give drugs a powerful antibacterial component.

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“The R2 pyocin is an extraordinary molecular machine that uses energy from its own biological battery to function,” said Miller, who also is a professor of microbiology, immunology and molecular genetics. “It is ideal for engineering targeted antibiotics that kill the bad bacteria without disrupting a patient’s protective gut bacteria.” The scarcity of the technology and the expertise needed to use it make CNSI one of the world’s few facilities capable of imaging atomic structures like these nanomachines at atomic-level resolution, which is why researchers from around the world come to UCLA to use the Electron Imaging Center for Nanomachines, a fee-for-service laboratory open to any scientist in academia or industry.
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Scientists explain skin fusion at a molecular level

Scientists from the Goethe University (GU) Frankfurt, the European Molecular Biology Laboratory (EMBL) Heidelberg and the University of Zurich explain skin fusion at a molecular level and pinpoint the specific molecules that do the job in their latest publication in the journal ("Quantitative analysis of cytoskeletal reorganization during epithelial tissue sealing by large-volume electron tomography"). In order to prevent death by bleeding or infection, every wound (skin opening) must close at some point. The events leading to skin closure had been unclear for many years. Mikhail Eltsov (GU) and colleagues used fruit fly embryos as a model system to understand this process. Similarly to humans, fruit fly embryos at some point in their development have a large opening in the skin on their back that must fuse. This process is called zipping, because two sides of the skin are fastened in a way that resembles a zipper that joins two sides of a jacket. zipping skin cells Perspective view of the zipping area with 17 skin cells "zipping". Membranes are colored in shades of brown and green to discriminate individual skin cells coming from the left or the right. The cells expand various types of protrusions in all directions to find their respective neighbor. The scientists have used a top-of-the-range electron microscope to study exactly how this zipping of the skin works. “Our electron microscope allows us to distinguish the molecular components in the cell that act like small machines to fuse the skin. When we look at it from a distance, it appears as if skin cells simply fuse to each other, but if we zoom in, it becomes clear that membranes, molecular machines, and other cellular components are involved", explains Eltsov. “In order to visualize this orchestra of healing, a very high-resolution picture of the process is needed. For this purpose we have recorded an enormous amount of data that surpasses all previous studies of this kind”, says Mikhail Eltsov. As a first step, as the scientists discovered, cells find their opposing partner by “sniffing” each other out. As a next step, they develop adherens junctions which act like a molecular Velcro. This way they become strongly attached to their opposing partner cell. The biggest revelation of this study was that small tubes in the cell, called microtubules, attach to this molecular Velcro and then deploy a self-catastrophe, which results in the skin being pulled towards the opening, as if one pulls a blanket over. Damian Brunner who led the team at the University of Zurich has performed many genetic manipulations to identify the correct components. The scientists were astonished to find that microtubules involved in cell-division are the primary scaffold used for zipping, indicating a mechanism conserved during evolution. “What was also amazing was the tremendous plasticity of the membranes in this process which managed to close the skin opening in a very short space of time. When five to ten cells have found their respective neighbors, the skin already appears normal”, says Achilleas Frangakis from the Goethe University Frankfurt, who led the study. The scientists hope that their results will open new avenues into the understanding of epithelial plasticity and wound healing. They are also investigating the detailed structural organization of the adherens junctions, work for which they were awarded a starting grant from European Research Council (ERC).
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Nanobubbles dilemma solved after more than twenty years

It was a question that has kept physicists and chemists busy for more than twenty years. Why can tiny bubbles in a liquid supersaturated with gas remain stable for weeks, while according to theoretical expectation they should disappear in a fraction of a second? Prof. dr. ir. Detlef Lohse from the University of Twente's MESA+ research institute found the answer. The research was recently published in the scientific journal ("Pinning and gas oversaturation imply stable single surface nanobubbles"). If a water repellent substrate is immersed in water containing dissolved gas, tiny bubbles can form on the immersed body. These so called surface nanobubbles emerge because the surrounding liquid wants to lose its gas, similar as bubbles emerge in a glass of soda. In the case of the nanobubbles, however, the bubbles are only ten to twenty nanometres in height (one nanometre is one million times smaller than a millimetre), and therefore the (Laplace) pressure in the bubble is very high. According to all the current theories, the bubbles should disappear on their own accord in less than a millisecond, since the gas in the bubbles wants to dissolve in the water again. According to Lohse, this idea is quite similar to a balloon, which - even if it is properly tied - always deflates over time. The reason for this is that a little bit of air constantly leaks through the rubber of the balloon due to diffusion and the high pressure in the balloon. Conclusive explanation In practice, however, the nanobubbles can survive for weeks, as was already observed more than twenty years ago. Nevertheless, scientists failed to find a conclusive explanation for this long lifetime. With the publication of an article in the scientific journal Physical Review E (Rapid Communication), prof. dr. ir. Detlef Lohse and prof. dr. Xuehua Zhang (who besides the UT is also affiliated with the RMIT University in Melbourne) finally provide an explanation for the phenomenon. And they do this with a complete analytical method with relatively simple mathematical formulas. Angle of curvature The reason that the bubbles survive for such a long period of time lies in the pinning of the three phase contact line. Thanks to the pinning, bubble shrinkage implies an increase of the radius of curvature and thus a smaller Laplace pressure. For stable bubbles the outflux originating from the Laplace pressure and the influx due to oversaturation balance. The result is a stable equilibrium. The research not only provides an answer to a fundamental physical and chemical question, but also has all sorts of practical applications. The knowledge can, for example, be used to make catalytic reactions more efficient and for flotation processes, a purification technique that is used a lot in the extraction of minerals. Research Within his Physics of Fluids (POF) Department at the University of Twente, Lohse has already been working on this topic for more than ten years. In this research, he works closely with prof. dr. ir. Harold Zandvliet from the Physics of Interfaces and Nanomaterials (PIN) department. The research is part of the MCEC Gravity Programme, within which the University of Utrecht, the Eindhoven University of Technology and the University of Twente work together on the development of efficient catalytic processes for different energy and material resources, such as fossil fuels, biomass and solar energy. NWO is financing this programme with 31.9 million euros.
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Better battery imaging paves way for renewable energy future

In a move that could improve the energy storage of everything from portable electronics to electric microgrids, University of Wisconsin-Madison and Brookhaven National Laboratory researchers have developed a novel X-ray imaging technique to visualize and study the electrochemical reactions in lithium-ion rechargeable batteries containing a new type of material, iron fluoride. "Iron fluoride has the potential to triple the amount of energy a conventional lithium-ion battery can store," says Song Jin, a UW-Madison professor of chemistry and Wisconsin Energy Institute affiliate. "However, we have yet to tap its true potential." Graduate student Linsen Li worked with Jin and other collaborators to perform experiments with a state-of-the-art transmission X-ray microscope at the National Synchrotron Light Source at Brookhaven. There, they collected chemical maps from actual coin cell batteries filled with iron fluoride during battery cycling to determine how well they perform. The results are published in the journal ("Visualization of electrochemically driven solid-state phase transformations using operando hard X-ray spectro-imaging"). Chemical phase map showing the electrochemical discharge of iron fluoride microwires Chemical phase map showing how the electrochemical discharge of iron fluoride microwires proceeded from 0 percent discharge (left), to 50 percent (middle), to 95 percent. (Image: Linsen Li) "In the past, we weren't able to truly understand what is happening to iron fluoride during battery reactions because other battery components were getting in the way of getting a precise image," says Li. By accounting for the background signals that would otherwise confuse the image, Li was able to accurately visualize and measure, at the nanoscale, the chemical changes iron fluoride undergoes to store and discharge energy. Thus far, using iron fluoride in rechargeable lithium ion batteries has presented scientists with two challenges. The first is that it doesn't recharge very well in its current form. "This would be like your smart phone only charging half as much the first time, and even less thereafter," says Li. "Consumers would rather have a battery that charges consistently through hundreds of charges." By examining iron fluoride transformation in batteries at the nanoscale, Jin and Li's new X-ray imaging method pinpoints each individual reaction to understand why capacity decay may be occurring. "In analyzing the X-ray data on this level, we were able to track the electrochemical reactions with far more accuracy than previous methods, and determined that iron fluoride performs better when it has a porous microstructure," says Li. The second challenge is that iron fluoride battery materials don't discharge as much energy as they take in, reducing energy efficiency. The current study yielded some preliminary insights into this problem and Jin and Li plan to tackle this challenge in future experiments. Some implications of this research are obvious — like using portable electronic devices for longer before charging — but Jin also foresees a bigger and broader range of applications. "If we can maximize the cycling performance and efficiency of these low-cost and abundant iron fluoride lithium ion battery materials, we could advance large-scale renewable energy storage technologies for electric cars and microgrids," he says. Some implications of this research are obvious — like using portable electronic devices for longer before charging — but Jin also foresees a bigger and broader range of applications. Jin also believes that the novel X-ray imaging technique will facilitate the studies of other technologically important solid-state transformations and help to improve processes such as preparation of inorganic ceramics and thin-film solar cells. The experiments were performed with the help of Yu-chen Karen Chen-Wiegart, Feng Wang, Jun Wang and their co-workers at Beamline X8C, National Synchrotron Light Source, Brookhaven National Laboratory, and supported by the U.S. Department of Energy Basic Energy Sciences and a seed grant from the Wisconsin Energy Institute. The synthesis of the battery materials in Jin's lab was supported by National Science Foundation Division of Materials Research.
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Researchers succeed in light-controlled molecule switching

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Konstanz are working on storing and processing information on the level of single molecules to create the smallest possible components that will combine autonomously to form a circuit. As recently reported in the academic journal ("Light-Induced Switching of Tunable Single-Molecule Junctions"), the researchers can switch on the current flow through a single molecule for the first time with the help of light. Dr. Artur Erbe, physicist at the HZDR, is convinced that in the future molecular electronics will open the door for novel and increasingly smaller – while also more energy efficient - components or sensors: “Single molecules are currently the smallest imaginable components capable of being integrated into a processor.” Scientists have yet to succeed in tailoring a molecule so that it can conduct an electrical current and that this current can be selectively turned on and off like an electrical switch. molecule Light on – molecule on. For the first time a light beam switches a single molecule to closed state (red atoms). At the ends of the diarylethene molecule gold electrodes are attached. This way, the molecule functions as an electrical switch. (Image: HZDR/Pfefferkorn ) This requires a molecule in which an otherwise strong bond between individual atoms dissolves in one location – and forms again precisely when energy is pumped into the structure. Dr. Jannic Wolf, chemist at the University of Konstanz, discovered through complex experiments that a particular diarylethene compound is an eligible candidate. The advantages of this molecule, approximately three nanometres in size, are that it rotates very little when a point in its structure opens and it possesses two nanowires that can be used as contacts. The diarylethene is an insulator when open and becomes a conductor when closed. It thus exhibits a different physical behaviour, a behaviour that the scientists from Konstanz and Dresden were able to demonstrate with certainty in numerous reproducible measurements for the first time in a single molecule. A computer from a test-tube A special feature of these molecular electronics is that they take place in a fluid within a test-tube, where the molecules are contacted within the solution. In order to ascertain what effects the solution conditions have on the switching process, it was therefore necessary to systematically test various solvents. The diarylethene needs to be attached at the end of the nanowires to electrodes so that the current can flow. “We developed a nanotechnology at the HZDR that relies on extremely thin tips made of very few gold atoms. We stretch the switchable diarylethene compound between them,” explains Dr. Erbe. When a beam of light then hits the molecule, it switches from its open to its closed state, resulting in a flowing current. “For the first time ever we could switch on a single contacted molecule and prove that this precise molecule becomes a conductor on which we have used the light beam," says Dr. Erbe, pleased with the results. "We have also characterized the molecular switching mechanism in extremely high detail, which is why I believe that we have succeeded in making an important step toward a genuine molecular electronic component.” Switching off, however, does not yet work with the contacted diarylethene, but the physicist is confident: “Our colleagues from the HZDR theory group are computing how precisely the molecule must rotate so that the current is interrupted. Together with the chemists from Konstanz, we will be able to accordingly implement the design and synthesis for the molecule.” However, a great deal of patience is required because it’s a matter of basic research. The diarylethene molecule contact using electron-beam lithography and the subsequent measurements alone lasted three long years. Approximately ten years ago, a working group at the University of Groningen in the Netherlands had already managed to construct a switch that could interrupt the current. The off-switch also worked only in one direction, but what couldn't be proven at the time with certainty was that the change in conductivity was bound to a single molecule. Nano-electronics in Dresden One area of research focus in Dresden is what is known as self-organization. “DNA molecules are, for instance, able to arrange themselves into structures without any outside assistance. If we succeed in constructing logical switches from self-organizing molecules, then computers of the future will come from test-tubes," Dr. Erbe prophesizes. The enormous advantages of this new technology are obvious: billion-euro manufacturing plants that are necessary for manufacturing today’s microelectronics could be a thing of the past. The advantages lie not only in production but also in operating the new molecular components, as they both will require very little energy.
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UNL wins $9.6 million NSF grant for nanotechnology research center

The University of Nebraska-Lincoln has earned a $9.6 million grant from the National Science Foundation to support its Materials Research Science and Engineering Center and its nanotechnology research through 2020. Through this multidisciplinary center, UNL physicists, chemists and engineers collaborate to study nanostructures and materials that could lead to more energy-efficient electronic devices. UNL's is one of 21 NSF-funded MRSECs nationwide. UNL established its MRSEC in 2002 with a $5.4 million NSF grant. In 2008, NSF awarded UNL $8.1 million to continue the center. UNL was one of 12 universities nationwide that received grants in the latest round of competition. "With this award from NSF, we continue to be part of a prestigious group of institutions recognized for our expertise in materials research and education through the MRSEC program, which includes Columbia, Harvard, MIT, the University of Chicago, Penn State and Ohio State," said UNL Chancellor Harvey Perlman. "The achievements of our materials researchers are highly valued by U.S. and international scientific communities and greatly contribute to UNL's reputation." The center receives a new name with this latest funding -- Polarization and Spin Phenomena in Nanoferroic Structures, or P-SPINS -- to reflect its expanding research focus on nanoferroic materials, which may one day transform electronics and computing technologies. "Our MRSEC scientists are doing research at the frontiers of materials and nanoscience and although this is very basic research, it leads to advanced technologies and products that affect our everyday lives," said Prem S. Paul, UNL vice chancellor for research and economic development. "An important part of the center's work is developing collaborations with industry and national laboratories to focus on potential applications." The center's success is based on several major accomplishments in understanding the properties and performance of nanomaterials, key steps toward improving computing power and creating advanced technologies, said Evgeny Tsymbal, George Holmes University Professor of Physics and MRSEC director. These discoveries have led the center to focus on two key areas: magnetoelectric materials and functional interfaces, and polarization-enabled electronic phenomena. UNL physicist Christian Binek leads the magnetoelectric materials and functional interfaces research group. It's based on Binek's work with spintronics, which manipulates electron spin, in addition to charge, to generate power and store digital information. Traditional magnetic memory devices use an electric current to reverse the magnetic direction, which is the binary method of storing information. Binek's team discovered how to switch magnetization using voltage instead, which doesn't generate heat and thus opens the avenue to energy-efficient computing. This team now is developing voltage-powered logical and memory devices. UNL physicist Alexei Gruverman leads the polarization-enabled electronic phenomena research group. This research takes advantage of nano-thin ferroelectric oxide, a material with both positive and negative polarization directions that, like spintronics, can be read out as a binary code using less energy than current technology. The work is driven by Tsymbal's theoretical predication and Gruverman's experimental demonstration of quantum tunneling across nano-thin ferroelectrics. The phenomenon of quantum tunneling, in which particles, such as electrons, can pass through a barrier, occurs only at the quantum, or atomic, level. When voltage is applied, electrons are able to tunnel through the barrier, creating a current with resistance. By experimenting with tunnel junctions, in which an ultra-thin barrier made of ferroelectric oxide is placed between two electrodes, they have shown that reversing the polarization changes dramatically the resistance through the tunnel junction. Measuring that resistance would allow devices to read the binary polarization direction, and thus, the information it contains. Each of these nanomaterials holds promise for overcoming the limitations of traditional silicon-based electronics, which engineers say are fast approaching their functional limits. Harnessing nanomaterials would enable smaller, more powerful and less expensive computers and other electronics. Other applications include more energy-efficient solar panels and refrigeration. "Our niche, which I think is very exciting in terms of fundamental science, is very important from the point of view of applications," Tsymbal said. "It's a focused research area where we're leading the field." The center's work is highly collaborative, with researchers from diverse disciplines sharing expertise. UNL's MRSEC includes 18 UNL faculty from the departments of physics and astronomy, chemistry, electrical engineering, mechanical and materials engineering, and teaching, learning and teacher education. Two other MRSEC affiliates are at North Carolina A&T State University and the University of Wisconsin-Madison. UNL MRSEC faculty collaborate with industry, national laboratories and scientists internationally and will interact closely with UNL's Center for Nanoferroic Devices, established in 2013 and funded jointly by a consortium of industrial companies known as the Nanoelectronics Research Initiative and the National Institute for Standards and Technology, to develop device applications. The latest NSF funding also will support expansion of the center's traditionally strong education and outreach programs. UNL physicist Axel Enders will lead several ongoing and new initiatives, including those designed to encourage women and minorities into materials science research. Activities include conferences and mentorship programs with minority-serving institutions, such as the University of Puerto Rico and North Carolina A&T State University. During summer research programs, undergraduates and faculty from non-research-intensive four-year institutions, as well as high school and middle school teachers, will continue to tackle research projects alongside the center's faculty and staff.
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