A mathematical model of heat flow through miniature wires could help develop thermoelectric devices that efficiently convert heat — even their own waste heat — into electricity. Developed at A*STAR, the model describes the movement of vibrations called phonons, which are responsible for carrying heat in insulating materials. Phonons typically move in straight lines in nanowires — threads barely a few atoms wide. Previous calculations suggested that if parts of a nanowire contained random arrangements of two different types of atoms, phonons would be stopped in their tracks. In actual alloy nanowires, though, atoms of the same element might cluster together to form short sections composed of the same elements. Now, Zhun-Yong Ong and Gang Zhang of the A*STAR Institute of High Performance Computing in Singapore have calculated the effects of such short-range order on the behavior of phonons ("Enhancement and reduction of one-dimensional heat conduction with correlated mass disorder"). Their results suggest that heat conduction in a nanowire does not just depend on the relative concentrations of the alloy atoms and the difference in their masses; it also depends on how the atoms are distributed. Their model simulated an 88-micrometer-long nanowire containing 160,000 atoms of two different elements. They found that when the nanowire was more ordered — containing clusters of the same elements — low-frequency phonons struggled to move. In contrast, high-frequency phonons could travel much further than the average length of the ordered regions in the alloy. “The high-frequency phonons were more mobile than we imagined,” says Ong. The researchers used their model to study the thermal resistance of a nanowire containing an equal mix of silicon and germanium atoms. Short-range ordering of the atoms allowed high-frequency phonons to travel freely through the wire, giving it a relatively low thermal resistance. In contrast, a random distribution of alloy atoms resulted in a higher resistance — over triple that of the ordered case for a 2.5-micrometer-long wire. “If this disorder can be realized in real composite materials then we could tailor the thermal conductivity of the system,” says Ong. Understanding the relative contribution of low- and high-frequency phonons to heat conduction could also help researchers tune the thermal properties of nanowires in the laboratory. “For instance, the surface roughening of nanowires is known to reduce the thermal conductivity contribution of high-frequency phonons,” says Ong. The researchers hope their model will help scientists design composite materials with low thermal conductivity. One attractive application is thermoelectric devices, explains Ong. “As these devices rely on a thermal differential, a low thermal conductivity is desirable for optimal performance.”
Thermal properties of nanowires - Follow the heat
read more "Thermal properties of nanowires - Follow the heat"
Promising thermo-magnetic data-storage technology with nanoislands
The mechanics and dynamics of heat-assisted magnetic recording (HAMR) are now better understood thanks to work by A*STAR and the National University of Singapore ("A study on dynamic heat assisted magnetization reversal mechanisms under insufficient reversal field conditions"). The experimental study will help scientists aiming to break the areal density barrier of current magnetic hard disk technology. 
A scanning electron micrograph of an array of 50-nm-diameter magnetic islands used to simulate a heat-assisted magnetic recording (HAMR) data storage medium. Today’s hard disk drives record and store data in minute magnetic domains on a spinning magnetic platter. As the magnetic domains become smaller, the thermal noise rises rapidly, making it increasingly difficult to record data reliably. HAMR is a promising future data storage scheme that uses a more stable magnetic medium, in combination with local heating, to achieve more reliable magnetization switching. “HAMR can be implemented with magnetic grains as small as 3 nanometers and higher magnetic anisotropy, which will make it possible to store magnetic information at recording densities beyond a terabyte per square inch,” says research leader Yunjie Chen from A*STAR’s Data Storage Institute. Theoretical simulations have demonstrated the potential of HAMR but also the possibility of density-limiting electrical noise and problematic non-reversal of magnetic domains in the recording process. Chen’s team designed some experiments to probe the dynamics of HAMR. “For practical application of HAMR, it is important to understand the thermo-magnetic reversal process and recording performance, including magnetization dynamics and effects that limit areal density,” says Chen. The experimental HAMR recording system devised by Chen’s team consisted of an array of magnetic islands of multilayer cobalt and palladium. Preparing this device involved sputtering multiple atomic layers of different combinations of elements, then patterning the device using electron-beam lithography to produce magnetic islands of about 50 nanometers in size (see image). The team then used far-field laser heating with a thermal spot size of about 1.5 micrometers in combination with a magnetic field to simulate the magnetization switching of the HAMR process. They observed the resultant magnetization patterns using a high-resolution magnetic force microscope. Chen’s team showed that when the material was laser heated to near its Curie temperature — the temperature at which the material’s permanent magnetism is overcome by an external magnetic field — the strength of the magnetic field required to induce complete magnetic switching was about 13 per cent of the intrinsic magnetic ‘coercivity’ of the islands. Surprisingly, however, the team also discovered that, due to thermal fluctuations, the optimal temperature for recording is slightly lower than the Curie temperature. Chen explains that the results provide critical operational parameters for the practical implementation of HAMR data storage technology.
A scanning electron micrograph of an array of 50-nm-diameter magnetic islands used to simulate a heat-assisted magnetic recording (HAMR) data storage medium. Today’s hard disk drives record and store data in minute magnetic domains on a spinning magnetic platter. As the magnetic domains become smaller, the thermal noise rises rapidly, making it increasingly difficult to record data reliably. HAMR is a promising future data storage scheme that uses a more stable magnetic medium, in combination with local heating, to achieve more reliable magnetization switching. “HAMR can be implemented with magnetic grains as small as 3 nanometers and higher magnetic anisotropy, which will make it possible to store magnetic information at recording densities beyond a terabyte per square inch,” says research leader Yunjie Chen from A*STAR’s Data Storage Institute. Theoretical simulations have demonstrated the potential of HAMR but also the possibility of density-limiting electrical noise and problematic non-reversal of magnetic domains in the recording process. Chen’s team designed some experiments to probe the dynamics of HAMR. “For practical application of HAMR, it is important to understand the thermo-magnetic reversal process and recording performance, including magnetization dynamics and effects that limit areal density,” says Chen. The experimental HAMR recording system devised by Chen’s team consisted of an array of magnetic islands of multilayer cobalt and palladium. Preparing this device involved sputtering multiple atomic layers of different combinations of elements, then patterning the device using electron-beam lithography to produce magnetic islands of about 50 nanometers in size (see image). The team then used far-field laser heating with a thermal spot size of about 1.5 micrometers in combination with a magnetic field to simulate the magnetization switching of the HAMR process. They observed the resultant magnetization patterns using a high-resolution magnetic force microscope. Chen’s team showed that when the material was laser heated to near its Curie temperature — the temperature at which the material’s permanent magnetism is overcome by an external magnetic field — the strength of the magnetic field required to induce complete magnetic switching was about 13 per cent of the intrinsic magnetic ‘coercivity’ of the islands. Surprisingly, however, the team also discovered that, due to thermal fluctuations, the optimal temperature for recording is slightly lower than the Curie temperature. Chen explains that the results provide critical operational parameters for the practical implementation of HAMR data storage technology.Smart micelles for marine environments
‘Smart’ materials that alter their structure in response to specific, controllable stimuli have applications in various fields, from biomedical science to the oil industry. Now, A*STAR researchers have created a self-assembling polymeric material that changes its structure when moved from water to an electrolyte solution, such as salt water ("Dual hydrophilic and salt responsive schizophrenic block copolymers – synthesis and study of self-assembly behavior"). The material could help improve coatings used to protect surfaces from the build-up of biological contaminants, particularly surfaces under the sea. Materials composed of segments of two different monomers, each with different characteristics, are known as block copolymers. Vivek Vasantha at A*STAR Institute of Chemical and Engineering Sciences — together with scientists from across Singapore under the Innovative Marine Antifouling Solutions (IMAS) program — developed a new block copolymer that can self-assemble into spherical micelle structures in which one monomer forms the core and the other forms the outer shell. The monomers are the hydrophilic poly(ethylene glycol), or PEG, which mixes well with water, and the halophilic polysulfabetaine (PSB), which has a preference for salt solution. “We created salt-responsive block copolymers that self-assemble in water to form either ‘conventional’ or ‘inverse’ micelles,” states Vasantha. The conventional micelles form in deionized water and have a core of halophilic PSB with a hydrophilic PEG shell. However, the team showed that the micelles re-assemble themselves when immersed in salt solution; PEG formed the core, and PSB formed the shell to create an ‘inverse’ micelle. “The material is easily controlled by salt alone, rather than by a combination of several stimuli like pH, temperature or light, which some other smart materials require,” explains Vasantha. “It appears to be highly tolerant of fluctuations in pH and temperature too, which means it is potentially useful for dynamic marine environments.” The researchers mixed the block copolymers with primer to create a non-toxic coating to replace traditional antifouling paint. Current coatings to prevent fouling by marine organisms include toxic chemicals, and become ineffective after a short time because the additives in the coatings break down rapidly in sea water. Vasantha’s team applied the new coating to glass slides, which they then immersed in the sea for two weeks. “The antifouling behavior of coatings is normally tested in laboratory experiments,” says Vasantha. “Throughout our unique marine tests, the self-assembling micelles kept the coated surfaces intact and the coating displayed reasonable antifouling behavior by preventing settling by organisms such as barnacles.” The researchers anticipate that their smart material will have other potential applications in enhanced oil recovery and biomedical science.
Researchers achieve an unprecedented level of control over defects in liquid crystals (w/video)
Sitting with a joystick in the comfort of their chairs, scientists can play "rodeo" on a screen magnifying what is happening under their microscope. They rely on optical tweezers to manipulate an intangible ring created out of liquid crystal defects capable of attaching a microsphere to a long thin fibre. Maryam Nikkhou and colleagues from the Josef Stefan Institute, in Ljubljana, Slovenia, recently published in ("Topological binding and elastic interactions of microspheres and fibres in a nematic liquid crystal") the results of work performed under the supervision of Igor Musevic. They believe that their findings could ultimately open the door to controlling the flow of light using light of a specific frequency in the Gigahertz range in liquid crystal photonic microdevices. Watch the video from the article:
Liquid crystals are familiar to us from their application in LCD screens. What makes them so interesting is that they are rich in defects. Thanks to advances in manipulation tools such as optical tweezers, the authors were able to create an arbitrary number of defect pairs on a long thin fibre plunged into a nematic liquid crystal - an ordered fluid with long organic molecules all pointing in the same direction like sardines in a tin. Nikkhou and colleagues use very strong laser tweezers to locally melt the liquid crystal into a phase where the molecules are oriented in all directions, encircling one part of the fibre. They subsequently switch-off the laser light, resulting in the locally molten liquid crystal rapidly cooling down. Its molecules then revert back from being oriented in all directions to being parallel to each other, creating several pairs of defects - akin to localised disruptions of the crystal's ordering field - forming a ring. Because liquid crystals are made of soft materials, their defects can be moved and modified easily. The defect ring is used as a non-material "rope" to entangle and strongly bind a microsphere and long fibre of micrometric diameter. Because these defects are typically preserved when subjected to stretching and bending, they offer an ideal physical model of an abstract field of mathematics called topology.
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Liquid crystals are familiar to us from their application in LCD screens. What makes them so interesting is that they are rich in defects. Thanks to advances in manipulation tools such as optical tweezers, the authors were able to create an arbitrary number of defect pairs on a long thin fibre plunged into a nematic liquid crystal - an ordered fluid with long organic molecules all pointing in the same direction like sardines in a tin. Nikkhou and colleagues use very strong laser tweezers to locally melt the liquid crystal into a phase where the molecules are oriented in all directions, encircling one part of the fibre. They subsequently switch-off the laser light, resulting in the locally molten liquid crystal rapidly cooling down. Its molecules then revert back from being oriented in all directions to being parallel to each other, creating several pairs of defects - akin to localised disruptions of the crystal's ordering field - forming a ring. Because liquid crystals are made of soft materials, their defects can be moved and modified easily. The defect ring is used as a non-material "rope" to entangle and strongly bind a microsphere and long fibre of micrometric diameter. Because these defects are typically preserved when subjected to stretching and bending, they offer an ideal physical model of an abstract field of mathematics called topology.
Skin tough
When weighing the pluses and minuses of your skin add this to the plus column: Your skin - like that of all vertebrates - is remarkably resistant to tearing. Now, a collaboration of researchers at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) San Diego has shown why. Making good use of the X-ray beams at Berkeley Lab's Advanced Light Source (ALS), the collaboration made the first direct observations of the micro-scale mechanisms behind the ability of skin to resist tearing. They identified four specific mechanisms in collagen, the main structural protein in skin tissue, that act synergistically to diminish the effects of stress. 
(Left) Collagen fibrils in the dermis of the skin are normally curvy and highly disordered, but (right) in response to a tear align themselves with the tension axis (arrow) to resist further damage. (courtesy of Berkeley Lab) "Collagen fibrils and fibers rotate, straighten, stretch and slide to carry load and reduce the stresses at the tip of any tear in the skin," says Robert Ritchie of Berkeley Lab's Materials Sciences Division, co-leader of this study along with UC San Diego's Marc Meyers. "The movement of the collagen acts to effectively diminish stress concentrations associated with any hole, notch or tear." Ritchie and Meyers are the corresponding authors of a paper in ("On the tear resistance of skin") that describes this study. Who among us does not pay close attention to the condition of our skin? While our main concern might be appearance, skin serves a multitude of vital purposes including protection from the environment, temperature regulation and thermal energy collection. The skin also serves as a host for embedded sensors. Skin consists of three layers - the epidermis, dermis and endodermis. Mechanical properties are largely determined in the dermis, which is the thickest layer and is made up primarily of collagen and elastin proteins. Collagen provides for mechanical resistance to extension, while elastin allows for deformation in response to low strains. Studies of the skin's mechanical properties date back to 1831 when a physician investigated stabbing wounds that the victim claimed were self-inflicted. This eventually led to scientists characterizing skin as a nonlinear-elastic material with low strain-rate sensitivity. In recent years research has focused on collagen deformation but with little attention paid to tearing even though skin has superior tear-resistance to other natural materials. "Our study is the first to model and directly observe in real time the micro-scale behavior of the collagen fibrils associated with the skin's remarkable tear resistance," Ritchie says. Ritchie, Meyers and their colleagues performed mechanical and structural characterizations during in situ tension-loading in the dermis. They did this through a combination of images obtained via ultrahigh-resolution scanning and transmission electron microscopy, and small-angle X-ray scattering (SAXS) at ALS beamline 7.3.3. "The method of SAXS that can be done at ALS beamline 7.3.3 is ideal for identifying strains in the collagen fibrils and watching how they move," Ritchie says. The research team began their work by establishing that a tear in the skin does not propagate or induce fracture, as does damage to bone or tooth dentin, which are comprised of mineralized collagen fibrils. What they demonstrated instead is that the tearing or notching of skin triggers structural changes in the collagen fibrils of the dermis layer to reduce the stress concentration. Initially, these collagen fibrils are curvy and highly disordered. However, in response to a tear they rearrange themselves towards the tensile-loading direction, with rotation, straightening, stretching, sliding and delamination prior to fracturing. "The rotation mechanisms recruit collagen fibrils into alignment with the tension axis at which they are maximally strong or can accommodate shape change," says Meyers. "Straightening and stretching allow the uptake of strain without much stress increase, and sliding allows more energy dissipation during inelastic deformation. This reorganization of the fibrils is responsible for blunting the stress at the tips of tears and notches." This new study of the skin is part of an on-going collaboration between Ritchie and Meyers to examine how nature achieves specific properties through architecture and structure. "Natural inspiration is a powerful motivation to develop new synthetic materials with unique properties," Ritchie says. "For example, the mechanistic understanding we've identified in skin could be applied to the improvement of artificial skin, or to the development of thin film polymers for applications such as flexible electronics."
(Left) Collagen fibrils in the dermis of the skin are normally curvy and highly disordered, but (right) in response to a tear align themselves with the tension axis (arrow) to resist further damage. (courtesy of Berkeley Lab) "Collagen fibrils and fibers rotate, straighten, stretch and slide to carry load and reduce the stresses at the tip of any tear in the skin," says Robert Ritchie of Berkeley Lab's Materials Sciences Division, co-leader of this study along with UC San Diego's Marc Meyers. "The movement of the collagen acts to effectively diminish stress concentrations associated with any hole, notch or tear." Ritchie and Meyers are the corresponding authors of a paper in ("On the tear resistance of skin") that describes this study. Who among us does not pay close attention to the condition of our skin? While our main concern might be appearance, skin serves a multitude of vital purposes including protection from the environment, temperature regulation and thermal energy collection. The skin also serves as a host for embedded sensors. Skin consists of three layers - the epidermis, dermis and endodermis. Mechanical properties are largely determined in the dermis, which is the thickest layer and is made up primarily of collagen and elastin proteins. Collagen provides for mechanical resistance to extension, while elastin allows for deformation in response to low strains. Studies of the skin's mechanical properties date back to 1831 when a physician investigated stabbing wounds that the victim claimed were self-inflicted. This eventually led to scientists characterizing skin as a nonlinear-elastic material with low strain-rate sensitivity. In recent years research has focused on collagen deformation but with little attention paid to tearing even though skin has superior tear-resistance to other natural materials. "Our study is the first to model and directly observe in real time the micro-scale behavior of the collagen fibrils associated with the skin's remarkable tear resistance," Ritchie says. Ritchie, Meyers and their colleagues performed mechanical and structural characterizations during in situ tension-loading in the dermis. They did this through a combination of images obtained via ultrahigh-resolution scanning and transmission electron microscopy, and small-angle X-ray scattering (SAXS) at ALS beamline 7.3.3. "The method of SAXS that can be done at ALS beamline 7.3.3 is ideal for identifying strains in the collagen fibrils and watching how they move," Ritchie says. The research team began their work by establishing that a tear in the skin does not propagate or induce fracture, as does damage to bone or tooth dentin, which are comprised of mineralized collagen fibrils. What they demonstrated instead is that the tearing or notching of skin triggers structural changes in the collagen fibrils of the dermis layer to reduce the stress concentration. Initially, these collagen fibrils are curvy and highly disordered. However, in response to a tear they rearrange themselves towards the tensile-loading direction, with rotation, straightening, stretching, sliding and delamination prior to fracturing. "The rotation mechanisms recruit collagen fibrils into alignment with the tension axis at which they are maximally strong or can accommodate shape change," says Meyers. "Straightening and stretching allow the uptake of strain without much stress increase, and sliding allows more energy dissipation during inelastic deformation. This reorganization of the fibrils is responsible for blunting the stress at the tips of tears and notches." This new study of the skin is part of an on-going collaboration between Ritchie and Meyers to examine how nature achieves specific properties through architecture and structure. "Natural inspiration is a powerful motivation to develop new synthetic materials with unique properties," Ritchie says. "For example, the mechanistic understanding we've identified in skin could be applied to the improvement of artificial skin, or to the development of thin film polymers for applications such as flexible electronics."Natural nanocrystals shown to strengthen concrete
Cellulose nanocrystals derived from industrial byproducts have been shown to increase the strength of concrete, representing a potential renewable additive to improve the ubiquitous construction material. s The cellulose nanocrystals (CNCs) could be refined from byproducts generated in the paper, bioenergy, agriculture and pulp industries. They are extracted from structures called cellulose microfibrils, which help to give plants and trees their high strength, lightweight and resilience. Now, researchers at Purdue University have demonstrated that the cellulose nanocrystals can increase the tensile strength of concrete by 30 percent. "This is an abundant, renewable material that can be harvested from low-quality cellulose feedstocks already being produced in various industrial processes," said Pablo Zavattieri, an associate professor in the Lyles School of Civil Engineering. The cellulose nanocrystals might be used to create a new class of biomaterials with wide-ranging applications, such as strengthening construction materials and automotive components. 
This transmission electron microscope image shows cellulose nanocrystals, tiny structures derived from renewable sources that might be used to create a new class of biomaterials with many potential applications. The structures have been shown to increase the strength of concrete. (Image: Purdue Life Sciences Microscopy Center) Research findings were published in February in the journal ("The influence of cellulose nanocrystal additions on the performance of cement paste"). The work was conducted by Jason Weiss, Purdue's Jack and Kay Hockema Professor of Civil Engineering and director of the Pankow Materials Laboratory; Robert J. Moon, a researcher from the U.S. Forest Service's Forest Products Laboratory; Jeffrey Youngblood, an associate professor of materials engineering; doctoral student Yizheng Cao; and Zavattieri. One factor limiting the strength and durability of today's concrete is that not all of the cement particles are hydrated after being mixed, leaving pores and defects that hamper strength and durability. "So, in essence, we are not using 100 percent of the cement," Zavattieri said. However, the researchers have discovered that the cellulose nanocrystals increase the hydration of the concrete mixture, allowing more of it to cure and potentially altering the structure of concrete and strengthening it. As a result, less concrete needs to be used. The cellulose nanocrystals are about 3 to 20 nanometers wide by 50-500 nanometers long - or about 1/1,000th the width of a grain of sand - making them too small to study with light microscopes and difficult to measure with laboratory instruments. They come from a variety of biological sources, primarily trees and plants. The concrete was studied using several analytical and imaging techniques. Because chemical reactions in concrete hardening are exothermic, some of the tests measured the amount of heat released, indicating an increase in hydration of the concrete. The researchers also hypothesized the precise location of the nanocrystals in the cement matrix and learned how they interact with cement particles in both fresh and hardened concrete. The nanocrystals were shown to form little inlets for water to better penetrate the concrete. The research dovetails with the goals of P3Nano, a public-private partnership supporting development and use of wood-based nanomaterial for a wide-range of commercial products. "The idea is to support and help Purdue further advance the CNC-Cement technology for full-scale field trials and the potential for commercialization," Zavattieri said.
This transmission electron microscope image shows cellulose nanocrystals, tiny structures derived from renewable sources that might be used to create a new class of biomaterials with many potential applications. The structures have been shown to increase the strength of concrete. (Image: Purdue Life Sciences Microscopy Center) Research findings were published in February in the journal ("The influence of cellulose nanocrystal additions on the performance of cement paste"). The work was conducted by Jason Weiss, Purdue's Jack and Kay Hockema Professor of Civil Engineering and director of the Pankow Materials Laboratory; Robert J. Moon, a researcher from the U.S. Forest Service's Forest Products Laboratory; Jeffrey Youngblood, an associate professor of materials engineering; doctoral student Yizheng Cao; and Zavattieri. One factor limiting the strength and durability of today's concrete is that not all of the cement particles are hydrated after being mixed, leaving pores and defects that hamper strength and durability. "So, in essence, we are not using 100 percent of the cement," Zavattieri said. However, the researchers have discovered that the cellulose nanocrystals increase the hydration of the concrete mixture, allowing more of it to cure and potentially altering the structure of concrete and strengthening it. As a result, less concrete needs to be used. The cellulose nanocrystals are about 3 to 20 nanometers wide by 50-500 nanometers long - or about 1/1,000th the width of a grain of sand - making them too small to study with light microscopes and difficult to measure with laboratory instruments. They come from a variety of biological sources, primarily trees and plants. The concrete was studied using several analytical and imaging techniques. Because chemical reactions in concrete hardening are exothermic, some of the tests measured the amount of heat released, indicating an increase in hydration of the concrete. The researchers also hypothesized the precise location of the nanocrystals in the cement matrix and learned how they interact with cement particles in both fresh and hardened concrete. The nanocrystals were shown to form little inlets for water to better penetrate the concrete. The research dovetails with the goals of P3Nano, a public-private partnership supporting development and use of wood-based nanomaterial for a wide-range of commercial products. "The idea is to support and help Purdue further advance the CNC-Cement technology for full-scale field trials and the potential for commercialization," Zavattieri said.Fascinating quantum transport on a surface
Topological insulators are an exceptional group of materials. Their interior acts as an insulator, but the surface conducts electricity extremely well. Scientists at The Technische Universität München now could measure this for the first time directly, with extremely high temporal resolution and at room temperature. In addition, they succeeded to influence the direction of the surface currents with a polarized laser beam ("Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity"). 
Bismuth-selenide sample between two gold electrodes. (Image: Christoph Hohmann / NIM) About ten years ago, scientists discovered a group of materials called "topological insulators" with unusual properties. The interior acts as an insulator, but the top three nanometers conduct electricity better than average. The group of Professor Alexander Holleitner has succeeded for the first time, to measure this charge current with picosecond resolution at room temperature. They also made the sensational discovery that they can direct the current by the help of circularly polarized light. The best-known representatives of topological insulators are bismuth selenide or telluride. Scientists account a phenomenon of quantum physics for the exceptionally high conductivity of their surfaces. One observes that all electrons moving in the surface layers have a well-defined spin. Hereby, they differ "topologically" from electrons inside the material. The direction of the surface currents is directly linked with the electron spin. An electron with positive spin always flows in the opposite direction as an electron with negative spin. "The light polarization controls the direction of the photocurrents. This is very fascinating and it results from the coupling of the electron motion with its spin", says Alexander Holleitner. Current almost without resistance In conventional conductors backscattering of a part of the electrons, for example at defects in the material, results in a resistance. The electrons in topological insulators, however, are not stopped because of the fixed coupling of the spin and the electron direction. Thus the current flows nearly under ideal conditions. "Because of the suppressed backscattering of electrons, the energy consumption decreases. And this could be interesting, for example, for the use of these materials as semiconductors in high-performance data processing", explains first author Christoph Kastl, who carried out the experiments together with his colleague Christoph Karnetzky. Measurements at a picosecond timescale The Munich physicists use a unique measurement technique, with which they can detect very small electric currents directly and with a picosecond time-resolution. For the actual experiment, they contacted a topological insulator between two electrodes and excited the material with a polarized femtosecond laser. Having a special high-frequency circuit, the scientists could track in real time how the surface currents spread within picoseconds. The trick is to measure the surface photocurrents, while the coupling between electron spin and direction is still maintained. A few picoseconds later, additional currents start to flow inside the material, on which the polarization of the stimulating laser has no influence. Hereby, Holleitner and his group could directly explore the onset of such additional thermo-electric currents in a real-time fashion. Therefore, the experimental results are interesting for spintronic and thermo-electric circuits. The experiments are funded by the Deutsche Forschungsgemeinschaft within DFG Projects 3324/8-1 of the SPP 1666 “topological insulator“ and the excellence cluster “Nanosystems Initiative Munich“ (NIM) and the European Science Council (ERC Grant „NanoREAL“).
Bismuth-selenide sample between two gold electrodes. (Image: Christoph Hohmann / NIM) About ten years ago, scientists discovered a group of materials called "topological insulators" with unusual properties. The interior acts as an insulator, but the top three nanometers conduct electricity better than average. The group of Professor Alexander Holleitner has succeeded for the first time, to measure this charge current with picosecond resolution at room temperature. They also made the sensational discovery that they can direct the current by the help of circularly polarized light. The best-known representatives of topological insulators are bismuth selenide or telluride. Scientists account a phenomenon of quantum physics for the exceptionally high conductivity of their surfaces. One observes that all electrons moving in the surface layers have a well-defined spin. Hereby, they differ "topologically" from electrons inside the material. The direction of the surface currents is directly linked with the electron spin. An electron with positive spin always flows in the opposite direction as an electron with negative spin. "The light polarization controls the direction of the photocurrents. This is very fascinating and it results from the coupling of the electron motion with its spin", says Alexander Holleitner. Current almost without resistance In conventional conductors backscattering of a part of the electrons, for example at defects in the material, results in a resistance. The electrons in topological insulators, however, are not stopped because of the fixed coupling of the spin and the electron direction. Thus the current flows nearly under ideal conditions. "Because of the suppressed backscattering of electrons, the energy consumption decreases. And this could be interesting, for example, for the use of these materials as semiconductors in high-performance data processing", explains first author Christoph Kastl, who carried out the experiments together with his colleague Christoph Karnetzky. Measurements at a picosecond timescale The Munich physicists use a unique measurement technique, with which they can detect very small electric currents directly and with a picosecond time-resolution. For the actual experiment, they contacted a topological insulator between two electrodes and excited the material with a polarized femtosecond laser. Having a special high-frequency circuit, the scientists could track in real time how the surface currents spread within picoseconds. The trick is to measure the surface photocurrents, while the coupling between electron spin and direction is still maintained. A few picoseconds later, additional currents start to flow inside the material, on which the polarization of the stimulating laser has no influence. Hereby, Holleitner and his group could directly explore the onset of such additional thermo-electric currents in a real-time fashion. Therefore, the experimental results are interesting for spintronic and thermo-electric circuits. The experiments are funded by the Deutsche Forschungsgemeinschaft within DFG Projects 3324/8-1 of the SPP 1666 “topological insulator“ and the excellence cluster “Nanosystems Initiative Munich“ (NIM) and the European Science Council (ERC Grant „NanoREAL“).3D imaging of objects with details as small as 25 nanometers
Scientists at the Paul Scherrer Institute and ETH Zurich (Switzerland) have created 3D images of tiny objects showing details down to 25 nanometres. In addition to the shape, the scientists determined how particular chemical elements were distributed in their sample and whether these elements were in a chemical compound or in their pure state. 
3D image of the buckyball structure investigated. In the right picture the distribution of Cobalt is shown in orange. The measurements were performed at the Swiss Light Source at the Paul Scherrer Institute using a method called phase tomography. As in other types of tomography, here x-rays are shone through the sample from different directions to give images from many perspectives. These images are combined using a computer program to give a 3D image. The method was demonstrated using a football-like structure called a “buckyball”, only 6 thousandths of a millimetre across, which was fabricated with the latest 3D laser technology. In addition to showing the shape of the object, the method allowed the scientists to pinpoint the locations of a specific chemical element (Cobalt) and deduce further information on the environment of its atoms. They made use of the fact that different elements interact differently with light of different energies, like different colours in visible light, allowing them to see the distribution of a specific element within the sample. Being able to distinguish different elements and their compounds on the nanometre scale in three dimensions is highly relevant in the development of novel electronic and magnetic parts or more efficient catalysts for the chemical industry.
3D image of the buckyball structure investigated. In the right picture the distribution of Cobalt is shown in orange. The measurements were performed at the Swiss Light Source at the Paul Scherrer Institute using a method called phase tomography. As in other types of tomography, here x-rays are shone through the sample from different directions to give images from many perspectives. These images are combined using a computer program to give a 3D image. The method was demonstrated using a football-like structure called a “buckyball”, only 6 thousandths of a millimetre across, which was fabricated with the latest 3D laser technology. In addition to showing the shape of the object, the method allowed the scientists to pinpoint the locations of a specific chemical element (Cobalt) and deduce further information on the environment of its atoms. They made use of the fact that different elements interact differently with light of different energies, like different colours in visible light, allowing them to see the distribution of a specific element within the sample. Being able to distinguish different elements and their compounds on the nanometre scale in three dimensions is highly relevant in the development of novel electronic and magnetic parts or more efficient catalysts for the chemical industry.Wrapping carbon nanotubes in polymers enhances their performance
Scientists first reported carbon nanotubes in the early 1990s. Since then, these tiny cylinders have been part of the quest to reduce the size of technological devices and their components. Carbon nanotubes (CNTs) have very desirable properties. They are 100 times stronger than steel and one-sixth its weight. They have several times the electrical and thermal conductivity of copper. And they have almost none of the environmental or physical degradation issues common to most metals, such as thermal contraction and expansion or erosion. CNTs have a tendency to aggregate, forming "clumps" of tubes. To utilize their outstanding properties in applications, they need to be dispersed. But they are insoluble in many liquids, making their even dispersion difficult. Scientists at Japan's Kyushu University developed a technique that "exfoliates" aggregated clumps of CNTs and disperses them in solvents. It involves wrapping the tubes in a polymer using a bond that does not involve the sharing of electrons. The technique is called non-covalent polymer wrapping. Whereas sharing electrons through covalent polymer wrapping leads to a more stable bond, it also changes the intrinsic desirable properties of the carbon nanotubes. Non-covalent wrapping is thus considered superior in most cases because it causes minimum damage to the tubes. The scientists, Dr. Tsuyohiko Fujigaya and Dr. Naotoshi Nakashima, conducted a research review ("Non-covalent polymer wrapping of carbon nanotubes and the role of wrapped polymers as functional dispersants") to analyze the various approaches of polymer wrapping and to summarize the applications in which polymer-wrapped carbon nanotubes can be used. They found that a wide variety of polymers can be used for the non-covalent wrapping of carbon nanotubes. Recently, many polymer dispersants have indeed been developed that not only disperse the CNTs but also add new functions to them. These polymer dispersants are now widely recognized and utilized in many fields, including biotechnology and energy applications. CNTs that are stably wrapped with biocompatible materials are very attractive in biomedicine, for example, due to their incredible ability to pass biological barriers without generating an immune response. There is thus high potential for polymer-wrapped CNTs in the area of drug delivery. Also, wrapping carbon nanotubes in polymers improves their photovoltaic functions in solar cells, for example, when the polymers function like a light-receiving pigment. Because the designs of polymers can be readily tailored, it is expected that the functionality of polymer-wrapped CNTs will be further expanded and that novel applications using them will be developed.
Novel nanocomposite coatings combine protection with colour effects
New colored protective coatings offer the same corrosion and wear protection as colorless coatings while their colouration opens new opportunities. Red could for instance be used as a warning color on surfaces which can get very hot. The new possibilities from combining protection and color in such coatings will be demonstrated by INM – Leibniz Institute for New Materials at this year’s Hannover Fair from 13 to 17 April as an exhibitor at the leading Research & Technology trade fair (stand B46 in hall 2). “Incorporating colored pigments in nanocomposites make coatings possible which are not only protective but also deliver additional visual information via their colouration,” explains Peter William de Oliveira, head of the IZI - Innovation Center INM. A protective coating for surfaces of ovens, chimneys or certain automotive parts could be colored red for instance. So such parts would not only be protected from corrosion, wear and oxidation but at the same time also be distinctive to the consumer by virtue of their color To create a full red shade without brown content, INM researchers are currently working on ceramic particles with red pigments free from iron oxide. Chemical compounds previously used were not very suitable for such applications. “Organic compounds do make for very nice reds – but they are unsuitable for such protective coatings, since organics do not survive high temperatures,” explains the physicist de Oliveira, “Iron oxides do withstand high temperatures when used as coloring particles for reds, but do not give full reds.” Black colored coatings with a thickness of two to five micrometers can withstand temperatures up to 900 degrees Celsius, but also coatings with a reddish brown color with resistance can endure up to 500 degrees Celsius. INM researchers are also developing protective coatings using blue and green pigments. Current developments at INM enable the use of these colored glass-ceramic layers on metals and glasses. The pigments are incorporated in sol-gel nanocomposites and applied by dipping or spraying.
A first glimpse inside a macroscopic quantum state
In a recent study published in ("Macroscopic quantum state analyzed particle by particle"), the research group led by ICREA Prof at ICFO Morgan Mitchell has detected, for the first time, entanglement among individual photon pairs in a beam of squeezed light. 
This is an artist's impression of a beam of entangled photons. (Image: ICFO) Quantum entanglement is always related to the microscopic world, but it also has striking macroscopic effects, such as the squeezing of light or superconductivity, a physical phenomenon that allows high-speed trains to levitate. Squeezed light is not physically compressed but it is it manipulated in such a way that one of its properties is super well defined, for example its polarization. Compared with normal light, laser light, composed of independent photons, has an extremely small but nonzero polarization uncertainty. This uncertainty or "quantum noise" is directly linked to the existence of photons, the smallest energy quanta of light. Now, squeezed light has an uncertainty that is farther below this level. Therefore, in optical communications, squeezed light can help transmit much weaker signals with the same signal to noise ratio and the same light power. It can also be used to distribute secret keys to two distant parties through quantum cryptography. Although it has long been believed that many macroscopic phenomena are caused by large-scale entanglement, up to now, this link has only been proposed theoretically. On the other hand, current computer simulations of entangled particles have not been able to help discern any new properties regarding this relationship since the memory and processor time required grow exponentially with the number of entangled particles, thus limiting the studies to only a few particles. Albeit these issues, spin-squeezing experiments have been able to claim the observation of many entangled atoms, but these claims are indirect since they have measured the macroscopic properties and used theory to infer the entanglement. ICREA Prof at ICFO Morgan Mitchell comments, "I am continually amazed by quantum mechanics. When the theoretical predictions came out, saying that there should be a sea of entangled particles inside a squeezed state, I was floored. I knew we had to do an experiment to see this up close". Now for the first time, ICFO scientists have been able to directly and experimentally confirm this link. To do so, they fabricated a beam of squeezed light, predicted to consist almost entirely of entangled photons. Then they extracted a small number of photons at random and measured their quantum state, in particular the joint polarization state of photon pairs. After overcoming many experimental obstacles, they found, in agreement with theoretical predictions, that any two photons near each other are entangled. By changing the density of the beam, they also observed effects of entanglement monogamy, where particles can be strongly entangled only if they have few entanglement partners. Federica Beduini states that "the experiment was terribly difficult; we had to combine squeezing with entangled-photon detection. There were many unsolved problems. We had to invent many things, like super-narrow optical filters, just to make the experiment possible". The results of this study show promising advances for other macroscopic many-body systems and quantum gases such as Bose-Einstein condensates for the future study of superconductivity and superfluidity, optical communications, or the research and development of qubits for quantum computing.
This is an artist's impression of a beam of entangled photons. (Image: ICFO) Quantum entanglement is always related to the microscopic world, but it also has striking macroscopic effects, such as the squeezing of light or superconductivity, a physical phenomenon that allows high-speed trains to levitate. Squeezed light is not physically compressed but it is it manipulated in such a way that one of its properties is super well defined, for example its polarization. Compared with normal light, laser light, composed of independent photons, has an extremely small but nonzero polarization uncertainty. This uncertainty or "quantum noise" is directly linked to the existence of photons, the smallest energy quanta of light. Now, squeezed light has an uncertainty that is farther below this level. Therefore, in optical communications, squeezed light can help transmit much weaker signals with the same signal to noise ratio and the same light power. It can also be used to distribute secret keys to two distant parties through quantum cryptography. Although it has long been believed that many macroscopic phenomena are caused by large-scale entanglement, up to now, this link has only been proposed theoretically. On the other hand, current computer simulations of entangled particles have not been able to help discern any new properties regarding this relationship since the memory and processor time required grow exponentially with the number of entangled particles, thus limiting the studies to only a few particles. Albeit these issues, spin-squeezing experiments have been able to claim the observation of many entangled atoms, but these claims are indirect since they have measured the macroscopic properties and used theory to infer the entanglement. ICREA Prof at ICFO Morgan Mitchell comments, "I am continually amazed by quantum mechanics. When the theoretical predictions came out, saying that there should be a sea of entangled particles inside a squeezed state, I was floored. I knew we had to do an experiment to see this up close". Now for the first time, ICFO scientists have been able to directly and experimentally confirm this link. To do so, they fabricated a beam of squeezed light, predicted to consist almost entirely of entangled photons. Then they extracted a small number of photons at random and measured their quantum state, in particular the joint polarization state of photon pairs. After overcoming many experimental obstacles, they found, in agreement with theoretical predictions, that any two photons near each other are entangled. By changing the density of the beam, they also observed effects of entanglement monogamy, where particles can be strongly entangled only if they have few entanglement partners. Federica Beduini states that "the experiment was terribly difficult; we had to combine squeezing with entangled-photon detection. There were many unsolved problems. We had to invent many things, like super-narrow optical filters, just to make the experiment possible". The results of this study show promising advances for other macroscopic many-body systems and quantum gases such as Bose-Einstein condensates for the future study of superconductivity and superfluidity, optical communications, or the research and development of qubits for quantum computing.Frustration produces a quantum playground
The construction of model quantum systems or simulators that can reveal hidden insights into other, less accessible quantum states requires paying attention to interactions normally overlooked by most theories, finds a RIKEN-led study ("Microscopic Model Calculations for the Magnetization Process of Layered Triangular-Lattice Quantum Antiferromagnets"). The research team has uncovered evidence of a weak force in a quantum simulator prototype that can answer questions about phase transitions involving Heisenberg's uncertainty principle and supersolids — matter with both superfluid and crystalline order that behaves like a viscosity-free liquid. 
A new type of quantum state that forms between neighboring spin clusters in layered triangular-lattice magnets is sensitive enough to act as a quantum simulator — a probe of quantum behavior in other materials. (Image: Giacomo Marmorini, RIKEN Condensed Matter Theory Laboratory) One promising quantum simulator is a class of insulating crystals known as triangular-lattice antiferromagnets (TLAFs). These compounds feature sheets of magnetic atoms, each containing single unpaired spin states, bonded into perfect triangular lattices. The triangular geometry prevents the magnetic spins from finding their most energetically stable state, resulting in a ‘frustrated’ system that makes TLAFs superb probes of phase transitions brought on by quantum fluctuations. The newly found cobalt-based material Ba3CoSb2O9 appears to hold the most promise among TLAFs because it forms a nearly perfect triangular crystal with relatively simple magnetic interactions. Recent experimental measurements of Ba3CoSb2O9 single crystals, however, have revealed a peculiar magnetization anomaly: a sign of extra quantum spin states under high magnetic field that should not exist, according to most theories. Giacomo Marmorini and Ippei Danshita from RIKEN with Daisuke Yamamoto from Waseda University set out to solve this problem through ‘microscopic model’ theoretical calculations. This approach divides the TLAF lattice into multi-atom, triangular clusters that have the same equilibrium properties. By scaling from a minimal three-atom cluster to a near-infinite TLAF sheet, the team calculated how quantum effects emerged under different conditions of interacting spins. To make their model more realistic, they also included three-dimensional interactions between adjacent Ba3CoSb2O9 sheets. Numerical simulations revealed that the inclusion of interlayer coupling was crucial: the weak forces between sandwiched sheets disclosed another quantum phase transition that eluded traditional two-dimensional modeling (Fig. 1). “This might not seem intuitive, because interlayer coupling is more than an order of magnitude smaller than other forces in the plane,” says Marmorini. “But our work shows that ignoring such effects can yield results very distant from reality.” The scientists believe that their results could be useful for measuring the ‘critical exponents’ that define the behavior of substances such as supersolids. “For frustrated quantum systems, critical exponents cannot be calculated directly, even with our numerical methods,” notes Marmorini. “However, using Ba3CoSb2O9 as a quantum simulator could give unprecedented confirmation of these fundamental ideas.”
A new type of quantum state that forms between neighboring spin clusters in layered triangular-lattice magnets is sensitive enough to act as a quantum simulator — a probe of quantum behavior in other materials. (Image: Giacomo Marmorini, RIKEN Condensed Matter Theory Laboratory) One promising quantum simulator is a class of insulating crystals known as triangular-lattice antiferromagnets (TLAFs). These compounds feature sheets of magnetic atoms, each containing single unpaired spin states, bonded into perfect triangular lattices. The triangular geometry prevents the magnetic spins from finding their most energetically stable state, resulting in a ‘frustrated’ system that makes TLAFs superb probes of phase transitions brought on by quantum fluctuations. The newly found cobalt-based material Ba3CoSb2O9 appears to hold the most promise among TLAFs because it forms a nearly perfect triangular crystal with relatively simple magnetic interactions. Recent experimental measurements of Ba3CoSb2O9 single crystals, however, have revealed a peculiar magnetization anomaly: a sign of extra quantum spin states under high magnetic field that should not exist, according to most theories. Giacomo Marmorini and Ippei Danshita from RIKEN with Daisuke Yamamoto from Waseda University set out to solve this problem through ‘microscopic model’ theoretical calculations. This approach divides the TLAF lattice into multi-atom, triangular clusters that have the same equilibrium properties. By scaling from a minimal three-atom cluster to a near-infinite TLAF sheet, the team calculated how quantum effects emerged under different conditions of interacting spins. To make their model more realistic, they also included three-dimensional interactions between adjacent Ba3CoSb2O9 sheets. Numerical simulations revealed that the inclusion of interlayer coupling was crucial: the weak forces between sandwiched sheets disclosed another quantum phase transition that eluded traditional two-dimensional modeling (Fig. 1). “This might not seem intuitive, because interlayer coupling is more than an order of magnitude smaller than other forces in the plane,” says Marmorini. “But our work shows that ignoring such effects can yield results very distant from reality.” The scientists believe that their results could be useful for measuring the ‘critical exponents’ that define the behavior of substances such as supersolids. “For frustrated quantum systems, critical exponents cannot be calculated directly, even with our numerical methods,” notes Marmorini. “However, using Ba3CoSb2O9 as a quantum simulator could give unprecedented confirmation of these fundamental ideas.”Simple method of binding pollutants in water with nanoadsorbers
New types of membrane adsorbers remove unwanted particles from water and also, at the same time, dissolved substances such as the hormonally active bis-phenol A or toxic lead. To do this, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB imbed selective adsorber particles in filtration membranes. It was not until January 2015 that the European Food Safety Authority (EFSA) lowered the threshold value for bisphenol A in packaging. The hormonally active bulk chemical is among other things a basic material for polycarbonate from which, for example, CDs, plastic tableware or spectacles glasses are manufactured. Due to its chemical structure, bisphenol A is not completely degraded in the biological stages of treatment plants and is discharged into rivers and lakes by the purification facility. Activated carbon or adsorber materials are already used to remove chemicals, anti-biotics or heavy metals from waste or process water. However, a disadvantage of these highly porous materials is the long contact time that the pollutants require to diffuse into the pores. So that as many of the harmful substances as possible are captured even in a shorter time, the treatment plants use larger quantities of adsorbers in correspondingly large treatment basins. However, activated carbon can only be regenerated with a high energy input, resulting for the most part in the need to dispose of large quantities of material contaminated with pollutants. Also, membrane filtration with nanofiltration or reverse osmosis membranes, which can remove the contaminating substances, is not yet cost-effective for the removal of dissolved molecules from high-volume flows such as process or wastewater. Membranes filter the water through their pores when a pressure is built up on one side of the membrane, thus holding back larger molecules and solid particles. But the smaller the membrane pores are, the higher the pressure – and therefore the more energy – that is required to separate the substances from water. Membrane adsorbers – filtering and binding in one step Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have opted for a new approach that combines the advantages of both methods. When manufacturing the membranes they add small, polymeric adsorber particles. The resulting membrane adsorbers can – in addition to their filtration function – adsorptively bind substances dissolved in water ("Nanostructured Composite Adsorber Membranes for the Reduction of Trace Substances in Water: The Example of Bisphenol A"). “We make use of the porous structure of the membrane located underneath the separation layer. The pores have a highly specific surface so that as many particles as possible can be imbedded, and they also provide optimum accessibility,” says Dr. Thomas Schiestel, Head of the “Inorganic Interfaces and Membranes” working group at the Fraunhofer IGB. 
Membrane adsorber “Unlike conventional adsorbers, our membrane adsorbers transport the pollutants convectively. This means that, with the water flowing rapidly through the membrane pores, a contact time lasting only a few seconds is sufficient to adsorb pollutants on the particle surface,” says the scientist. Up to 40 percent of the weight of the membrane adsorbers is accounted for by the particles, so their binding capacity is correspondingly high. At the same time the membrane adsorbers can be operated at low pressures. As the membranes can be packed very tightly, very large volumes of water can be treated even with small devices. Functional adsorber particles The researchers manufacture the adsorber particles in a one-step, cost-efficient process. In this patented process monomeric components are polymerized with the help of a crosslinking agent to generate 50 to 500 nanometer polymer globules. “Depending on which substances are to be removed from the water, we select the most suitable one from a variety of monomers with differing functional groups,” Schiestel explains. The spectrum here ranges from pyridine, which tends to be hydrophobic, by way of cationic ammonium compounds and includes anionic phosphonates. Selective removal of pollutants and metals The researchers were able to show in various tests that the membrane adsorbers remove pollutants very selectively by means of the particles, which are customized for the particular contaminant in question. For example, membrane adsorbers with pyridine groups bind the hydrophobic bisphenol A especially well, whereas those with amino groups adsorb the negatively charged salt of the antibiotic penicillin G. “The various adsorber particles can even be combined in one membrane. In this way we can remove several micropollutants simultaneously with just one membrane adsorber,” says Schiestel, pointing out a further advantage. Equipped with different functional groups, the membrane adsorbers can also remove toxic heavy metals such as lead or arsenic from the water. Phosphonate membrane adsorbers, for example, adsorb more than 5 grams of lead per square meter of membrane surface area – 40 percent more than a commercially available membrane adsorber. Cost-effective and regenerable So that the membrane adsorbers can be used several times, the adsorbed pollutants have to be detached once again from the particles in the membrane. “Membrane adsorbers for bisphenol A can be fully regenerated by a shift of the pH value,” Schiestel explains. The concentrated pollutants can then be disposed off cost-effectively or broken down using suitable oxidative processes. The regenerability of the membrane adsorbers also makes possible a further application: reutilization of the separated molecules. This additionally makes the technology attractive for recovering valuable precious metals or rare earth metals.
Membrane adsorber “Unlike conventional adsorbers, our membrane adsorbers transport the pollutants convectively. This means that, with the water flowing rapidly through the membrane pores, a contact time lasting only a few seconds is sufficient to adsorb pollutants on the particle surface,” says the scientist. Up to 40 percent of the weight of the membrane adsorbers is accounted for by the particles, so their binding capacity is correspondingly high. At the same time the membrane adsorbers can be operated at low pressures. As the membranes can be packed very tightly, very large volumes of water can be treated even with small devices. Functional adsorber particles The researchers manufacture the adsorber particles in a one-step, cost-efficient process. In this patented process monomeric components are polymerized with the help of a crosslinking agent to generate 50 to 500 nanometer polymer globules. “Depending on which substances are to be removed from the water, we select the most suitable one from a variety of monomers with differing functional groups,” Schiestel explains. The spectrum here ranges from pyridine, which tends to be hydrophobic, by way of cationic ammonium compounds and includes anionic phosphonates. Selective removal of pollutants and metals The researchers were able to show in various tests that the membrane adsorbers remove pollutants very selectively by means of the particles, which are customized for the particular contaminant in question. For example, membrane adsorbers with pyridine groups bind the hydrophobic bisphenol A especially well, whereas those with amino groups adsorb the negatively charged salt of the antibiotic penicillin G. “The various adsorber particles can even be combined in one membrane. In this way we can remove several micropollutants simultaneously with just one membrane adsorber,” says Schiestel, pointing out a further advantage. Equipped with different functional groups, the membrane adsorbers can also remove toxic heavy metals such as lead or arsenic from the water. Phosphonate membrane adsorbers, for example, adsorb more than 5 grams of lead per square meter of membrane surface area – 40 percent more than a commercially available membrane adsorber. Cost-effective and regenerable So that the membrane adsorbers can be used several times, the adsorbed pollutants have to be detached once again from the particles in the membrane. “Membrane adsorbers for bisphenol A can be fully regenerated by a shift of the pH value,” Schiestel explains. The concentrated pollutants can then be disposed off cost-effectively or broken down using suitable oxidative processes. The regenerability of the membrane adsorbers also makes possible a further application: reutilization of the separated molecules. This additionally makes the technology attractive for recovering valuable precious metals or rare earth metals.The first observation of the effect of electron spin of molecular oxygen on the surface oxidation reaction
Mitsunori Kurahashi, a Chief Researcher of the Nano Characterization Unit (Unit Director: Daisuke Fujita), National Institute for Materials Science (President: Sukekatsu Ushioda) and Yasushi Yamauchi, a Group Leader in the same unit, presented the first spin-controlled O2 adsorption experiment indicating that the rate of surface oxidation is strongly affected by the electron spin of O2 ("Spin Correlation in O2 Chemisorption on Ni(111)"). 
(a) Control of the O2 spin direction by the defining magnetic field. (b) Spin-dependent O2 adsorption on a Ni(111) film surface. The adsorption probability is changed when the O2 spin direction relative to the majority spin direction of the Ni film (SM) is alternated. No spin-dependent effect is observed for O2 adsorption on a non-magnetic W(110) surface. O2 adsorption on material surfaces is important as the initial step of catalytic reaction, corrosion and oxide film formation. O2 is magnetic due to its electron spin derived from two unpaired electrons. The potential effect of the O2 spin on the adsorption process has been pointed out theoretically, but the effect has been unclear because there has been no experimental evidence for it. Kurahashi and Yamauchi have realized the spin- and alignment-resolved O2 adsorption experiment by combining the quantum-state-selected O2 beam, which has been originally developed by them, with a magnetized Ni film. Their experiment has shown that O2 adsorption probability depends on the orientation of the O2 spin relative to the magnetization of the Ni film. The spin dependency is significant especially at low kinetic energy conditions, and amounts to more than 40% at thermal energy. These results indicate that thermal oxidation rate of ferromagnetic materials such as iron and nickel depends strongly on the spin orientation between O2 and the surface. It has been concluded that the magnetic exchange interaction between O2 and the surface is the main cause of the observed spin dependency. It is well known that solid and/or liquid oxygen exhibit magnetism, but this research presented the first experimental evidence that the magnetic property of O2 has a strong influence on its chemical reactivity. This research has established a new methodology for analyzing the spin effect in O2-surface interactions. Also, the observed clear spin effect may provide a firm basis to advance the theoretical technique for simulating oxygen adsorption. This research was conducted as part of the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research/Basic Research (B) “Development of a Single Spin-Rotational State-Selected O2 Beam and its Application to Surface Reaction Analysis,” sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT).
(a) Control of the O2 spin direction by the defining magnetic field. (b) Spin-dependent O2 adsorption on a Ni(111) film surface. The adsorption probability is changed when the O2 spin direction relative to the majority spin direction of the Ni film (SM) is alternated. No spin-dependent effect is observed for O2 adsorption on a non-magnetic W(110) surface. O2 adsorption on material surfaces is important as the initial step of catalytic reaction, corrosion and oxide film formation. O2 is magnetic due to its electron spin derived from two unpaired electrons. The potential effect of the O2 spin on the adsorption process has been pointed out theoretically, but the effect has been unclear because there has been no experimental evidence for it. Kurahashi and Yamauchi have realized the spin- and alignment-resolved O2 adsorption experiment by combining the quantum-state-selected O2 beam, which has been originally developed by them, with a magnetized Ni film. Their experiment has shown that O2 adsorption probability depends on the orientation of the O2 spin relative to the magnetization of the Ni film. The spin dependency is significant especially at low kinetic energy conditions, and amounts to more than 40% at thermal energy. These results indicate that thermal oxidation rate of ferromagnetic materials such as iron and nickel depends strongly on the spin orientation between O2 and the surface. It has been concluded that the magnetic exchange interaction between O2 and the surface is the main cause of the observed spin dependency. It is well known that solid and/or liquid oxygen exhibit magnetism, but this research presented the first experimental evidence that the magnetic property of O2 has a strong influence on its chemical reactivity. This research has established a new methodology for analyzing the spin effect in O2-surface interactions. Also, the observed clear spin effect may provide a firm basis to advance the theoretical technique for simulating oxygen adsorption. This research was conducted as part of the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research/Basic Research (B) “Development of a Single Spin-Rotational State-Selected O2 Beam and its Application to Surface Reaction Analysis,” sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT).Gold nanoparticles size up to cancer treatment
Treatments that attack cancer cells through the targeted silencing of cancer genes could be developed using small interfering RNA molecules (siRNA). However delivering the siRNA into the cells intact is a challenge as it is readily degraded by enzymes in the blood and small enough to be eliminated from the blood stream by kidney filtration. Now Kazunori Kataoka at the University of Tokyo and colleagues at Tokyo Institute of Technology have designed a protective treatment delivery vehicle with optimum stability and size for delivering siRNA to cells (, "Precise engineering of siRNA delivery vehicles to tumors using polyion complexes and gold nanoparticles"). 
Top: Stability assay of the siRNA-loaded polymer complex (labelled uPIC, unimer polyion complex) without and with gold nanoparticles (AuNP) incubated with heparin at 0, 1, 2, and 3 µg/mL, and glutathione (GSH) at 0 and 10 mM. Bottom: Schematic illustration of the proposed mechanism for intracellular siRNA release from uPIC-AuNPs in the presence of GSH. (click on image to enlarge) The researchers formed a polymer complex with a single siRNA molecule. The siRNA-loaded complex was then bonded to a 20 nm gold nanoparticle, which thanks to advances in synthesis techniques can be produced with a reliably low size distribution. The resulting nanoarchitecture had the optimum overall size - small enough to infiltrate cells while large enough to accumulate. In an assay containing heparin – a biological anti-coagulant with a high negative charge density – the complex was found to release the siRNA due to electrostatic interactions. However when the gold nanoparticle was incorporated the complex remained stable. Instead, release of the siRNA from the complex with the gold nanoparticle could be triggered once inside the cell by the presence of glutathione, which is present in high concentrations in intracellular fluid. The glutathione bonded with the gold nanoparticles and the complex, detaching them from each other and leaving the siRNA prone to release. The researchers further tested their carrier in a subcutaneous tumour model. The authors concluded that the complex bonded to the gold nanoparticle “enabled the efficient tumor accumulation of siRNA and significant in vivo gene silencing effect in the tumor, demonstrating the potential for siRNA-based cancer therapies.”
Top: Stability assay of the siRNA-loaded polymer complex (labelled uPIC, unimer polyion complex) without and with gold nanoparticles (AuNP) incubated with heparin at 0, 1, 2, and 3 µg/mL, and glutathione (GSH) at 0 and 10 mM. Bottom: Schematic illustration of the proposed mechanism for intracellular siRNA release from uPIC-AuNPs in the presence of GSH. (click on image to enlarge) The researchers formed a polymer complex with a single siRNA molecule. The siRNA-loaded complex was then bonded to a 20 nm gold nanoparticle, which thanks to advances in synthesis techniques can be produced with a reliably low size distribution. The resulting nanoarchitecture had the optimum overall size - small enough to infiltrate cells while large enough to accumulate. In an assay containing heparin – a biological anti-coagulant with a high negative charge density – the complex was found to release the siRNA due to electrostatic interactions. However when the gold nanoparticle was incorporated the complex remained stable. Instead, release of the siRNA from the complex with the gold nanoparticle could be triggered once inside the cell by the presence of glutathione, which is present in high concentrations in intracellular fluid. The glutathione bonded with the gold nanoparticles and the complex, detaching them from each other and leaving the siRNA prone to release. The researchers further tested their carrier in a subcutaneous tumour model. The authors concluded that the complex bonded to the gold nanoparticle “enabled the efficient tumor accumulation of siRNA and significant in vivo gene silencing effect in the tumor, demonstrating the potential for siRNA-based cancer therapies.”Carbon nanotube fibers make superior links to brain
Carbon nanotube fibers invented at Rice University may provide the best way to communicate directly with the brain. The fibers have proven superior to metal electrodes for deep brain stimulation and to read signals from a neuronal network. Because they provide a two-way connection, they show promise for treating patients with neurological disorders while monitoring the real-time response of neural circuits in areas that control movement, mood and bodily functions. 
Pairs of carbon nanotube fibers have been tested for potential use as implantable electrodes to treat patients with neurological disorders like Parkinson's disease. The fibers invented at Rice University proved to be far better than metallic wires now used to stimulate neurons in the brain. (Courtesy of the Pasquali Lab) New experiments at Rice demonstrated the biocompatible fibers are ideal candidates for small, safe electrodes that interact with the brain’s neuronal system, according to the researchers. They could replace much larger electrodes currently used in devices for deep brain stimulation therapies in Parkinson’s disease patients. They may also advance technologies to restore sensory or motor functions and brain-machine interfaces as well as deep brain stimulation therapies for other neurological disorders, including dystonia and depression, the researchers wrote. The paper appeared online this week in the American Chemical Society journal ("Neural Stimulation and Recording with Bidirectional, Soft Carbon Nanotube Fiber Microelectrodes"). The fibers created by the Rice lab of chemist and chemical engineer Matteo Pasquali consist of bundles of long nanotubes originally intended for aerospace applications where strength, weight and conductivity are paramount. The individual nanotubes measure only a few nanometers across, but when millions are bundled in a process called wet spinning, they become thread-like fibers about a quarter the width of a human hair. “We developed these fibers as high-strength, high-conductivity materials,” Pasquali said. “Yet, once we had them in our hand, we realized that they had an unexpected property: They are really soft, much like a thread of silk. Their unique combination of strength, conductivity and softness makes them ideal for interfacing with the electrical function of the human body.” The simultaneous arrival in 2012 of Caleb Kemere, a Rice assistant professor who brought expertise in animal models of Parkinson’s disease, and lead author Flavia Vitale, a research scientist in Pasquali’s lab with degrees in chemical and biomedical engineering, prompted the investigation. “The brain is basically the consistency of pudding and doesn’t interact well with stiff metal electrodes,” Kemere said. “The dream is to have electrodes with the same consistency, and that’s why we’re really excited about these flexible carbon nanotube fibers and their long-term biocompatibility.” Flavia Vitale, a postdoctoral researcher at Rice, prepares carbon nanotube fibers for testing. Vitale is lead author of a new study that determined the thread-like fibers made of millions of carbon nanotubes may be suitable as electrodes to stimulate the brains of patients with neurological diseases. Photo by Jeff Fitlow Weeks-long tests on cells and then in rats with Parkinson’s symptoms proved the fibers are stable and as efficient as commercial platinum electrodes at only a fraction of the size. The soft fibers caused little inflammation, which helped maintain strong electrical connections to neurons by preventing the body’s defenses from scarring and encapsulating the site of the injury. The highly conductive carbon nanotube fibers also show much more favorable impedance – the quality of the electrical connection — than state-of-the-art metal electrodes, making for better contact at lower voltages over long periods, Kemere said. The working end of the fiber is the exposed tip, which is about the width of a neuron. The rest is encased with a three-micron layer of a flexible, biocompatible polymer with excellent insulating properties. The challenge is in placing the tips. “That’s really just a matter of having a brain atlas, and during the experiment adjusting the electrodes very delicately and putting them into the right place,” said Kemere, whose lab studies ways to connect signal-processing systems and the brain’s memory and cognitive centers. Doctors who implant deep brain stimulation devices start with a recording probe able to “listen” to neurons that emit characteristic signals depending on their functions, Kemere said. Once a surgeon finds the right spot, the probe is removed and the stimulating electrode gently inserted. Rice carbon nanotube fibers that send and receive signals would simplify implantation, Vitale said. Caleb Kemere shows a brain atlas as he discusses new research aimed at using carbon nanotube fibers invented at Rice as electrodes for deep brain stimulation of patients with neurological disorders like Parkinson's disease. The flexible fibers are much smaller than the metallic electrodes they would replace and far more effective in stimulating and recording signals from neurons. Photo by Jeff Fitlow The fibers could lead to self-regulating therapeutic devices for Parkinson’s and other patients. Current devices include an implant that sends electrical signals to the brain to calm the tremors that afflict Parkinson’s patients. “But our technology enables the ability to record while stimulating,” Vitale said. “Current electrodes can only stimulate tissue. They’re too big to detect any spiking activity, so basically the clinical devices send continuous pulses regardless of the response of the brain.” Kemere foresees a closed-loop system that can read neuronal signals and adapt stimulation therapy in real time. He anticipates building a device with many electrodes that can be addressed individually to gain fine control over stimulation and monitoring from a small, implantable device. “Interestingly, conductivity is not the most important electrical property of the nanotube fibers,” Pasquali said. “These fibers are intrinsically porous and extremely stable, which are both great advantages over metal electrodes for sensing electrochemical signals and maintaining performance over long periods of time.”
Pairs of carbon nanotube fibers have been tested for potential use as implantable electrodes to treat patients with neurological disorders like Parkinson's disease. The fibers invented at Rice University proved to be far better than metallic wires now used to stimulate neurons in the brain. (Courtesy of the Pasquali Lab) New experiments at Rice demonstrated the biocompatible fibers are ideal candidates for small, safe electrodes that interact with the brain’s neuronal system, according to the researchers. They could replace much larger electrodes currently used in devices for deep brain stimulation therapies in Parkinson’s disease patients. They may also advance technologies to restore sensory or motor functions and brain-machine interfaces as well as deep brain stimulation therapies for other neurological disorders, including dystonia and depression, the researchers wrote. The paper appeared online this week in the American Chemical Society journal ("Neural Stimulation and Recording with Bidirectional, Soft Carbon Nanotube Fiber Microelectrodes"). The fibers created by the Rice lab of chemist and chemical engineer Matteo Pasquali consist of bundles of long nanotubes originally intended for aerospace applications where strength, weight and conductivity are paramount. The individual nanotubes measure only a few nanometers across, but when millions are bundled in a process called wet spinning, they become thread-like fibers about a quarter the width of a human hair. “We developed these fibers as high-strength, high-conductivity materials,” Pasquali said. “Yet, once we had them in our hand, we realized that they had an unexpected property: They are really soft, much like a thread of silk. Their unique combination of strength, conductivity and softness makes them ideal for interfacing with the electrical function of the human body.” The simultaneous arrival in 2012 of Caleb Kemere, a Rice assistant professor who brought expertise in animal models of Parkinson’s disease, and lead author Flavia Vitale, a research scientist in Pasquali’s lab with degrees in chemical and biomedical engineering, prompted the investigation. “The brain is basically the consistency of pudding and doesn’t interact well with stiff metal electrodes,” Kemere said. “The dream is to have electrodes with the same consistency, and that’s why we’re really excited about these flexible carbon nanotube fibers and their long-term biocompatibility.” Flavia Vitale, a postdoctoral researcher at Rice, prepares carbon nanotube fibers for testing. Vitale is lead author of a new study that determined the thread-like fibers made of millions of carbon nanotubes may be suitable as electrodes to stimulate the brains of patients with neurological diseases. Photo by Jeff Fitlow Weeks-long tests on cells and then in rats with Parkinson’s symptoms proved the fibers are stable and as efficient as commercial platinum electrodes at only a fraction of the size. The soft fibers caused little inflammation, which helped maintain strong electrical connections to neurons by preventing the body’s defenses from scarring and encapsulating the site of the injury. The highly conductive carbon nanotube fibers also show much more favorable impedance – the quality of the electrical connection — than state-of-the-art metal electrodes, making for better contact at lower voltages over long periods, Kemere said. The working end of the fiber is the exposed tip, which is about the width of a neuron. The rest is encased with a three-micron layer of a flexible, biocompatible polymer with excellent insulating properties. The challenge is in placing the tips. “That’s really just a matter of having a brain atlas, and during the experiment adjusting the electrodes very delicately and putting them into the right place,” said Kemere, whose lab studies ways to connect signal-processing systems and the brain’s memory and cognitive centers. Doctors who implant deep brain stimulation devices start with a recording probe able to “listen” to neurons that emit characteristic signals depending on their functions, Kemere said. Once a surgeon finds the right spot, the probe is removed and the stimulating electrode gently inserted. Rice carbon nanotube fibers that send and receive signals would simplify implantation, Vitale said. Caleb Kemere shows a brain atlas as he discusses new research aimed at using carbon nanotube fibers invented at Rice as electrodes for deep brain stimulation of patients with neurological disorders like Parkinson's disease. The flexible fibers are much smaller than the metallic electrodes they would replace and far more effective in stimulating and recording signals from neurons. Photo by Jeff Fitlow The fibers could lead to self-regulating therapeutic devices for Parkinson’s and other patients. Current devices include an implant that sends electrical signals to the brain to calm the tremors that afflict Parkinson’s patients. “But our technology enables the ability to record while stimulating,” Vitale said. “Current electrodes can only stimulate tissue. They’re too big to detect any spiking activity, so basically the clinical devices send continuous pulses regardless of the response of the brain.” Kemere foresees a closed-loop system that can read neuronal signals and adapt stimulation therapy in real time. He anticipates building a device with many electrodes that can be addressed individually to gain fine control over stimulation and monitoring from a small, implantable device. “Interestingly, conductivity is not the most important electrical property of the nanotube fibers,” Pasquali said. “These fibers are intrinsically porous and extremely stable, which are both great advantages over metal electrodes for sensing electrochemical signals and maintaining performance over long periods of time.”EPA proposes reporting and record keeping requirements on nanomaterials
The U.S. Environmental Protection Agency (EPA) is proposing one-time reporting and recordkeeping requirements on nanoscale chemical substances in the marketplace. “Nanotechnology holds great promise for improving products, from TVs and vehicles to batteries and solar panels, said Jim Jones, EPA’s Assistant Administrator for Chemical Safety and Pollution Prevention. “We want to continue to facilitate the trend toward this important technology. Today’s action will ensure that EPA also has information on nano-sized versions of chemicals that are already in the marketplace.” EPA currently reviews new chemical substances manufactured or processed as nanomaterials prior to introduction into the marketplace to ensure that they are safe. For the first time, the agency is proposing to use TSCA to collect existing exposure and health and safety information on chemicals currently in the marketplace when manufactured or processed as nanoscale materials. The proposal will require one-time reporting from companies that manufacture or process chemical substances as nanoscale materials. The companies will notify EPA of:
Nanoscale materials have special properties related to their small size such as greater strength and lighter weight, however, they may take on different properties than their conventionally-sized counterpart. The proposal is not intended to conclude that nanoscale materials will cause harm to human health or the environment; Rather, EPA would use the information gathered to determine if any further action under the Toxic Substances Control Act (TSCA), including additional information collection, is needed. The proposed reporting requirements are being issued under the authority of section 8(a) under TSCA. The agency is requesting public comment on the proposed reporting and recordkeeping requirements 90 days from publication in the Federal Register. EPA also anticipates holding a public meeting during the comment period. The time and place of the meeting will be announced on EPA’s web page at (add link) Additional information and a fact sheet on the specifics of the proposed rule and what constitutes a nanocale chemical material can be found at http://1.usa.gov/19lclav.
- certain information, including specific chemical identity;
- production volume;
- methods of manufacture; processing, use, exposure, and release information; and,
- available health and safety data.
Nanoscale materials have special properties related to their small size such as greater strength and lighter weight, however, they may take on different properties than their conventionally-sized counterpart. The proposal is not intended to conclude that nanoscale materials will cause harm to human health or the environment; Rather, EPA would use the information gathered to determine if any further action under the Toxic Substances Control Act (TSCA), including additional information collection, is needed. The proposed reporting requirements are being issued under the authority of section 8(a) under TSCA. The agency is requesting public comment on the proposed reporting and recordkeeping requirements 90 days from publication in the Federal Register. EPA also anticipates holding a public meeting during the comment period. The time and place of the meeting will be announced on EPA’s web page at (add link) Additional information and a fact sheet on the specifics of the proposed rule and what constitutes a nanocale chemical material can be found at http://1.usa.gov/19lclav.
Nanorobotic agents open the blood-brain barrier, offering hope for new brain treatments
Magnetic nanoparticles can open the blood-brain barrier and deliver molecules directly to the brain, say researchers from the University of Montreal, Polytechnique Montréal, and CHU Sainte-Justine ("Remote control of the permeability of the blood–brain barrier by magnetic heating of nanoparticles: A proof of concept for brain drug delivery"). This barrier runs inside almost all vessels in the brain and protects it from elements circulating in the blood that may be toxic to the brain. The research is important as currently 98% of therapeutic molecules are also unable to cross the blood-brain barrier. “The barrier is temporary opened at a desired location for approximately 2 hours by a small elevation of the temperature generated by the nanoparticles when exposed to a radio-frequency field,” explained first author and co-inventor Seyed Nasrollah Tabatabaei. “Our tests revealed that this technique is not associated with any inflammation of the brain. This new result could lead to a breakthrough in the way nanoparticles are used in the treatment and diagnosis of brain diseases,” explained the co-investigator, Hélène Girouard. “At the present time, surgery is the only way to treat patients with brain disorders. Moreover, while surgeons are able to operate to remove certain kinds of tumors, some disorders are located in the brain stem, amongst nerves, making surgery impossible,” added collaborator and senior author Anne-Sophie Carret. Although the technology was developed using murine models and has not yet been tested in humans, the researchers are confident that future research will enable its use in people. “Building on earlier findings and drawing on the global effort of an interdisciplinary team of researchers, this technology proposes a modern version of the vision described almost 40 years ago in the movie Fantastic Voyage, where a miniature submarine navigated in the vascular network to reach a specific region of the brain,” said principal investigator Sylvain Martel. In earlier research, Martel and his team had managed to manipulate the movement of nanoparticles through the body using the magnetic forces generated by magnetic resonance imaging (MRI) machines. To open the blood-brain barrier, the magnetic nanoparticles are sent to the surface of the blood-brain barrier at a desired location in the brain. Although it was not the technique used in this study, the placement could be achieved by using the MRI technology described above. Then, the researchers generated a radio-frequency field. The nanoparticles reacted to the radio-frequency field by dissipating heat thereby creating a mechanical stress on the barrier. This allows a temporary and localized opening of the barrier for diffusion of therapeutics into the brain. The technique is unique in many ways. “The result is quite significant since we showed in previous experiments that the same nanoparticles can also be used to navigate therapeutic agents in the vascular network using a clinical MRI scanner,” Martel remarked. “Linking the navigation capability with these new results would allow therapeutics to be delivered directly to a specific site of the brain, potentially improving significantly the efficacy of the treatment while avoiding systemic circulation of toxic agents that affect healthy tissues and organs,” Carret added. “While other techniques have been developed for delivering drugs to the blood-brain barrier, they either open it too wide, exposing the brain to great risks, or they are not precise enough, leading to scattering of the drugs and possible unwanted side effect,” Martel said. Although there are many hurdles to overcome before the technology can be used to treat humans, the research team is optimistic. “Although our current results are only proof of concept, we are on the way to achieving our goal of developing a local drug delivery mechanism that will be able to treat oncologic, psychiatric, neurological and neurodegenerative disorders, amongst others,” Carret concluded.
Switchable adhesion principle enables damage-free handling of sensitive devices even in vacuum
Components with highly sensitive surfaces are used in automotive, semiconductor and display technologies as well as for complex optical lens systems. During the production, these parts often have to be handled many times by pick-and-place processes. Each pick-up and release with conventional gripping systems involves the risk of either contamination of the surfaces with residues from transportation adhesives, or damage due to mechanical gripping. Suction cup systems diminish residues, but fail in a vacuum or on rough surfaces. Researchers at the Leibniz Institute for New Materials (INM) have now enhanced the Gecko adhesion principle such that adhesion can be switched on and off in vacuum. The researchers from the INM will be presenting their results from 13 to 17 April 2015 in Hall 2 at the stand B46 of the Hannover Messe in the context of the leading trade fair for R & D and Technology Transfer. 
Switchable adhesion principle enables damage-free handling of sensitive devices even in vacuum; (Image: Uwe Bellhäuser) "Artificially produced microscopic pillars, so-called gecko structures, adhere to various items. By manipulating these pillars, the adhesion can be switched on and off. Thus, items can be lifted and released quickly and precisely," Karsten Moh from the Program Division Functional Microstructures explains. "This technique is particularly interesting in vacuum, as suction cups fail there," says Moh. With the currently developed adhesion system, adhesive forces of more than 1 Newton per square centimeter can be achieved on smooth surfaces." In our tests, the system has proved successful even after 100,000 cycles", the upscaling expert Moh says. Even slightly rough surfaces can be handled reliably. The developers now focus on increasing the adhesion force to lift and release large components and heavy materials in an energy-efficient way. Furthermore the development group works on the gripping of objects with curved surfaces without leaving residues. Additionally, the scientists also focus on developing other triggers for switching the adhesion like light, magnetic field, electric field or changes in temperature. INM conducts research and development to create new materials – for today, tomorrow and beyond. Chemists, physicists, biologists, materials scientists and engineers team up to focus on these essential questions: Which material properties are new, how can they be investigated and how can they be tailored for industrial applications in the future? Four research thrusts determine the current developments at INM: New materials for energy application, new concepts for medical surfaces, new surface materials for tribological applications and nano safety and nano bio. Research at INM is performed in three fields: Nanocomposite Technology, Interface Materials, and Bio Interfaces.
Switchable adhesion principle enables damage-free handling of sensitive devices even in vacuum; (Image: Uwe Bellhäuser) "Artificially produced microscopic pillars, so-called gecko structures, adhere to various items. By manipulating these pillars, the adhesion can be switched on and off. Thus, items can be lifted and released quickly and precisely," Karsten Moh from the Program Division Functional Microstructures explains. "This technique is particularly interesting in vacuum, as suction cups fail there," says Moh. With the currently developed adhesion system, adhesive forces of more than 1 Newton per square centimeter can be achieved on smooth surfaces." In our tests, the system has proved successful even after 100,000 cycles", the upscaling expert Moh says. Even slightly rough surfaces can be handled reliably. The developers now focus on increasing the adhesion force to lift and release large components and heavy materials in an energy-efficient way. Furthermore the development group works on the gripping of objects with curved surfaces without leaving residues. Additionally, the scientists also focus on developing other triggers for switching the adhesion like light, magnetic field, electric field or changes in temperature. INM conducts research and development to create new materials – for today, tomorrow and beyond. Chemists, physicists, biologists, materials scientists and engineers team up to focus on these essential questions: Which material properties are new, how can they be investigated and how can they be tailored for industrial applications in the future? Four research thrusts determine the current developments at INM: New materials for energy application, new concepts for medical surfaces, new surface materials for tribological applications and nano safety and nano bio. Research at INM is performed in three fields: Nanocomposite Technology, Interface Materials, and Bio Interfaces.Possibilities for graphene-integrated polymer composites in dental prostheses ans medical implants
A larger proportion of our population is now living into their 80s and 90s and this has a great deal of influence on the frequency with which either partial and complete tooth loss occurs. There are other causes of edentulism outside of an ageing demographic of course - congenital absence, trauma, dental diseases and oral cancers all significantly contribute to it too. All of these factors, as well as increased interest in oral health within developing countries, are leading to a considerable growth in the value of the global dental prosthetic supply business. It is expected that this will be worth approximately $9.1 biliion by 2018, according to industry analysts Markets&Markets (an almost 50% increase on its current value). Around half of this will be related to fixed dental prostheses (either implant-supported bridges/crowns, tooth-supported bridges/crowns, inlays, onlays or veneers). If this the predicted increase in the market is to be witnessed, however, then major advances must be made in prothestic science. Numerous approaches have been taken to the construction of fixed dental prostheses, but existing material technologies have tended to fall short of expectations. The reason for this is an inherent lack of robustness, which leads to short operational lifespans being witnessed. Conversely, the period of time that prostheses need to function is being extended as the average life expectancy increases. There is an increasing demand within the dental industry for prosthetic materials which display increased overall resilience and permit greater longevity. One of the main problems associated with the fitting of patients with fixed dental prostheses is that of location. This stems from the fact they must be situated within the mouth - which proves to be an extremely demanding setting, where exposure to moisture, high temperatures, abrasion from toothbrushes and intake of food all have to be dealt with. These conditions can lead to complications, mechanical failures and contraindications occuring, all of which negate clinical success and over time mandate remedial work to restore the prosthetic to full working order - with associated cost and inconvenience. Then there is the issue of biocompatibility to consider. It is critical that any prostheses can coexist harmoniously with the organic tissues they are in contact with. The regularity with which failures currently occur prevents the specification of prostheses with operational lifespans which are in line with the patients (i.e. capable of functioning over decades rather than just years). This is something that must be satisfied before fixed dental prostheses are to gain widespread acceptance. To try and meet these requirements, a number of materials have been investigated in recent times - including metals (such as aluminium and tin), ceramics (zirconium and porcelain) and metal-ceramic hybrids. These materials have sadly proved inadequate in terms of their mechanical properties and their biocompatibly. Initiation of allergen sensitivity, potential for cytotoxicity, inability to blend in well enough with surrounding teeth/gums are other factors that need to be taken into account. Poly-ether-ether-ketone (PEEK) is an organic thermoplastic polymer material which is already employed in some medical implants due to its compatibility with human tissues. By integrating graphene into this polymer is hoped that the high degree of ruggedness that is mandated by dental use can be achieved. Graphene solutions provider 2-DTech and dental implant specialist Evodental are currently in the process of carrying out preliminary investigative work into the prospects of applying graphene within the field of dentistry. Utilising composites featuring high grade graphene they are looking to produce PEEK-based fixed dental prostheses with markedly increased longevity and improved clinical function. The objective of the project is to incorporate microscopic disc-shaped particles of graphene (known as graphene nanoplatelets) into the PEEK in order to form a graphene-reinforced polymer that is strong enough for dental prostheses (leading to a marked reduction in the number of clinical/surgical procedures needed to carry out repairs) while better matching the surface properties of the bone accommodating it and teeth around it. Combining an ultra-thin structure with high durability, the graphene-reinforced polymer envisaged by 2-DTech and Evodental could mitigate the deficiencies of current fixed dental prostheses construction methodologies. The resulting prostheses will benefit from the strength of graphene. Furthermore, since graphene coatings are completely transparent they have no effect on the prostheses’ visual appearance. Graphene-based polymer composites, such as the one described in this article, have the potential to revolutionise dentistry, enabling production of dental prostheses that are better able to cope with hostile operational environments. This will allow for greater prevalence of oral rehabilitation and thereby decrease the level of edentulism in the global population.
Nanotechnology platform shows promise for treating pancreatic cancer
Scientists at UCLA’s California NanoSystems Institute and Jonsson Comprehensive Cancer Center have combined their nanotechnology expertise to create a new treatment that may solve some of the problems of using chemotherapy to treat pancreatic cancer. The study, published online in the journal ("Use of a Lipid-Coated Mesoporous Silica Nanoparticle Platform for Synergistic Gemcitabine and Paclitaxel Delivery to Human Pancreatic Cancer in Mice"), describes successful experiments to combine two drugs within a specially designed mesoporous silica nanoparticle that looks like a glass bubble. The drugs work together to shrink human pancreas tumors in mice as successfully as the current standard treatment, but at one twelfth the dosage. This lower dosage could reduce both the cost of treatment and the side effects that people suffer from the current method. 
Paclitaxel/Gemcitabine co-delivery inhibits pancreatic cancer. The study was led by Dr. Huan Meng, assistant adjunct professor of medicine, and Dr. Andre Nel, distinguished professor of medicine, both at the Jonsson Cancer Center. Pancreatic cancer, a devastating disease with a five-year survival rate of 5 percent, is difficult to detect early and symptoms do not usually appear until the disease is advanced. As a result, many people are not diagnosed until their tumors are beyond the effective limits of surgery, leaving chemotherapy as the only viable treatment option. The chemotherapy drug most often used for pancreas cancer is gemcitabine, but its impact is often limited. Recent research has found that combining gemcitabine with another drug called paclitaxel can improve the overall treatment effect. In the current method, Abraxane — a nano complex containing paclitaxel — and gemcitabine are given separately, which works to a degree, but because the drugs may stay in the body for different lengths of time, the combined beneficial effect is not fully synchronized. “The beauty of the silica nanoparticle technology is that gemcitabine and paclitaxel are placed together in one special lipid-coated nanoparticle at the exact ratio that makes them synergistic with one another when co-delivered at the cancer site, giving us the best possible outcome by using a single drug carrier,” Meng said. “This enables us to reduce the dose and maintain the combinatorial effect.” After the scientists constructed the silica nanoparticles, they suspended them in blood serum and injected them into mice that had human pancreas tumors growing under their skin. Other mice with tumors were given injections of saline solution (a placebo with no effect), gemcitabine (the treatment standard), and gemcitabine and Abraxane (an FDA-approved combination shown to improve pancreas cancer survival in humans). In the mice that received the two drugs inside the nanoparticle, pancreas tumors shrank dramatically compared with those in the other mice. Similar comparisons were made with mouse models, in which the human tumors were surgically implanted into the mice’s abdomens in order to more closely emulate the natural point of origin of pancreatic tumors and provide a better parallel to the tumors in humans. In these experiments, the tumors in the mice receiving silica nanoparticles shrank more than the comparative controls. Also, metastasis, or tumor spread, to nearby organs was eradicated in these mice. “Instead of just a laboratory proof-of-principle study of any cancer, we specifically attacked pancreatic cancer with a custom-designed nanocarrier,” said Nel, who is also associate director for research of the California NanoSystems Institute. “In our platform, the drugs are truly synergistic because we have control over drug mixing, allowing us to incorporate optimal ratios in our particles, making the relevance of our models very high and our results very strong.” Meng said the silica nanocarrier must still be refined for use in humans. The researchers hope to test the platform in human clinical trials within the next five years.
Paclitaxel/Gemcitabine co-delivery inhibits pancreatic cancer. The study was led by Dr. Huan Meng, assistant adjunct professor of medicine, and Dr. Andre Nel, distinguished professor of medicine, both at the Jonsson Cancer Center. Pancreatic cancer, a devastating disease with a five-year survival rate of 5 percent, is difficult to detect early and symptoms do not usually appear until the disease is advanced. As a result, many people are not diagnosed until their tumors are beyond the effective limits of surgery, leaving chemotherapy as the only viable treatment option. The chemotherapy drug most often used for pancreas cancer is gemcitabine, but its impact is often limited. Recent research has found that combining gemcitabine with another drug called paclitaxel can improve the overall treatment effect. In the current method, Abraxane — a nano complex containing paclitaxel — and gemcitabine are given separately, which works to a degree, but because the drugs may stay in the body for different lengths of time, the combined beneficial effect is not fully synchronized. “The beauty of the silica nanoparticle technology is that gemcitabine and paclitaxel are placed together in one special lipid-coated nanoparticle at the exact ratio that makes them synergistic with one another when co-delivered at the cancer site, giving us the best possible outcome by using a single drug carrier,” Meng said. “This enables us to reduce the dose and maintain the combinatorial effect.” After the scientists constructed the silica nanoparticles, they suspended them in blood serum and injected them into mice that had human pancreas tumors growing under their skin. Other mice with tumors were given injections of saline solution (a placebo with no effect), gemcitabine (the treatment standard), and gemcitabine and Abraxane (an FDA-approved combination shown to improve pancreas cancer survival in humans). In the mice that received the two drugs inside the nanoparticle, pancreas tumors shrank dramatically compared with those in the other mice. Similar comparisons were made with mouse models, in which the human tumors were surgically implanted into the mice’s abdomens in order to more closely emulate the natural point of origin of pancreatic tumors and provide a better parallel to the tumors in humans. In these experiments, the tumors in the mice receiving silica nanoparticles shrank more than the comparative controls. Also, metastasis, or tumor spread, to nearby organs was eradicated in these mice. “Instead of just a laboratory proof-of-principle study of any cancer, we specifically attacked pancreatic cancer with a custom-designed nanocarrier,” said Nel, who is also associate director for research of the California NanoSystems Institute. “In our platform, the drugs are truly synergistic because we have control over drug mixing, allowing us to incorporate optimal ratios in our particles, making the relevance of our models very high and our results very strong.” Meng said the silica nanocarrier must still be refined for use in humans. The researchers hope to test the platform in human clinical trials within the next five years.Squid-inspired 'invisibility stickers' could help you evade detection in the dark (w/video)
Squid are the ultimate camouflage artists, blending almost flawlessly with their backgrounds so that unsuspecting prey can't detect them. Using a protein that's key to this process, scientists have designed "invisibility stickers" that could one day help soldiers disguise themselves, even when sought by enemies with tough-to-fool infrared cameras. The researchers will present their work today at the 249th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features nearly 11,000 presentations on a wide range of science topics. Take a look at a brand-new video on the research:
"Soldiers wear uniforms with the familiar green and brown camouflage patterns to blend into foliage during the day, but under low light and at night, they're still vulnerable to infrared detection," explains Alon Gorodetsky, Ph.D. "We've developed stickers for use as a thin, flexible layer of camo with the potential to take on a pattern that will better match the soldiers' infrared reflectance to their background and hide them from active infrared visualization." To work toward this effect, Gorodetsky of the University of California at Irvine (UCI) turned to squid skin for inspiration. Squid skin features unusual cells known as iridocytes, which contain layers or platelets composed of a protein called reflectin. The animal uses a biochemical cascade to change the thickness of the layers and their spacing. This in turn affects how the cells reflect light and thus, the skin's coloration. Gorodetsky's group coaxed bacteria to produce reflectin and then coated a hard substrate with the protein. To induce structural -- and light-reflecting -- changes just like those of iridocytes, the film needed some kind of trigger. An initial search revealed that acetic acid vapors could cause the film to swell and disappear when viewed with an infrared camera. But these conditions won't work for soldiers in the field. "What we were doing was the equivalent of bathing the film in acetic acid vapors -- essentially exposing it to concentrated vinegar," Gorodetsky says. "That is not practical for real-life use." Now Gorodetsky has fabricated reflectin films on conformable polymer substrates, effectively sticky tape one might find in any household. This tape can adhere to a range of surfaces including cloth uniforms, and its appearance under an infrared camera can be changed by stretching, a mechanical trigger that might more realistically be used in military operations. Although the technology isn't ready for field use just yet, he envisions soldiers or security personnel could one day carry in their packs a roll of invisibility stickers that they could cover their uniforms with as needed. "We're going after something that's inexpensive and completely disposable," he says. "You take out this protein-coated tape, you use it quickly to make an appropriate camouflage pattern on the fly, then you take it off and throw it away." Gorodetsky says that some major challenges remain. The team will have to figure out how to increase the brightness of the stickers and get multiple stickers to respond in the same way at the same time, as part of an adaptive camouflage system. He's also working on ways to make the stickers more versatile. The current version reflects near-infrared light. Gorodetsky's team is continuing to tweak the materials, so variants of the stickers could also work at mid- and far-infrared wavelengths. These could have applications for thwarting thermal infrared imaging. They also could have uses outside the military -- for example, in clothing that can selectively trap or release body heat to keep people comfortable in different environments. Moreover, in collaboration with Francesco Tombola, Ph.D., and Lisa Flanagan, Ph.D., from the UCI School of Medicine, Gorodetsky's lab has shown that reflectin supports cell growth. This could have implications for making new types of bioelectronic devices and even growing "living" semi-artificial squid skin. Title Infrared invisibility stickers inspired by cephalopods Abstract The skin structure of cephalopods endows them with remarkable dynamic camouflage capabilities. Consequently, much research effort has focused on understanding and emulating these animals' color changing abilities in the visible region of the electromagnetic spectrum. In contrast, despite the importance of infrared signaling and detection for many industrial and military applications, few studies have attempted to translate the principles underlying cephalopod adaptive coloration to infrared camouflage. We have drawn inspiration from nanostructures implicated in cephalopods' camouflage abilities and developed strategies for the self-assembly of unique cephalopod structural proteins into dynamically tunable biomimetic camouflage coatings on both transparent and flexible substrates. Our substrates can adhere to arbitrary surfaces, and their reflectance can be reversibly modulated from the visible to the near-infrared regions of the electromagnetic spectrum with both chemical and mechanical stimuli. Thus, we can endow common objects with any shape or form factor with tunable camouflage capabilities. Our work represents a key step toward the development of wearable biomimetic color and shapeshifting technologies for stealth applications.
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"Soldiers wear uniforms with the familiar green and brown camouflage patterns to blend into foliage during the day, but under low light and at night, they're still vulnerable to infrared detection," explains Alon Gorodetsky, Ph.D. "We've developed stickers for use as a thin, flexible layer of camo with the potential to take on a pattern that will better match the soldiers' infrared reflectance to their background and hide them from active infrared visualization." To work toward this effect, Gorodetsky of the University of California at Irvine (UCI) turned to squid skin for inspiration. Squid skin features unusual cells known as iridocytes, which contain layers or platelets composed of a protein called reflectin. The animal uses a biochemical cascade to change the thickness of the layers and their spacing. This in turn affects how the cells reflect light and thus, the skin's coloration. Gorodetsky's group coaxed bacteria to produce reflectin and then coated a hard substrate with the protein. To induce structural -- and light-reflecting -- changes just like those of iridocytes, the film needed some kind of trigger. An initial search revealed that acetic acid vapors could cause the film to swell and disappear when viewed with an infrared camera. But these conditions won't work for soldiers in the field. "What we were doing was the equivalent of bathing the film in acetic acid vapors -- essentially exposing it to concentrated vinegar," Gorodetsky says. "That is not practical for real-life use." Now Gorodetsky has fabricated reflectin films on conformable polymer substrates, effectively sticky tape one might find in any household. This tape can adhere to a range of surfaces including cloth uniforms, and its appearance under an infrared camera can be changed by stretching, a mechanical trigger that might more realistically be used in military operations. Although the technology isn't ready for field use just yet, he envisions soldiers or security personnel could one day carry in their packs a roll of invisibility stickers that they could cover their uniforms with as needed. "We're going after something that's inexpensive and completely disposable," he says. "You take out this protein-coated tape, you use it quickly to make an appropriate camouflage pattern on the fly, then you take it off and throw it away." Gorodetsky says that some major challenges remain. The team will have to figure out how to increase the brightness of the stickers and get multiple stickers to respond in the same way at the same time, as part of an adaptive camouflage system. He's also working on ways to make the stickers more versatile. The current version reflects near-infrared light. Gorodetsky's team is continuing to tweak the materials, so variants of the stickers could also work at mid- and far-infrared wavelengths. These could have applications for thwarting thermal infrared imaging. They also could have uses outside the military -- for example, in clothing that can selectively trap or release body heat to keep people comfortable in different environments. Moreover, in collaboration with Francesco Tombola, Ph.D., and Lisa Flanagan, Ph.D., from the UCI School of Medicine, Gorodetsky's lab has shown that reflectin supports cell growth. This could have implications for making new types of bioelectronic devices and even growing "living" semi-artificial squid skin. Title Infrared invisibility stickers inspired by cephalopods Abstract The skin structure of cephalopods endows them with remarkable dynamic camouflage capabilities. Consequently, much research effort has focused on understanding and emulating these animals' color changing abilities in the visible region of the electromagnetic spectrum. In contrast, despite the importance of infrared signaling and detection for many industrial and military applications, few studies have attempted to translate the principles underlying cephalopod adaptive coloration to infrared camouflage. We have drawn inspiration from nanostructures implicated in cephalopods' camouflage abilities and developed strategies for the self-assembly of unique cephalopod structural proteins into dynamically tunable biomimetic camouflage coatings on both transparent and flexible substrates. Our substrates can adhere to arbitrary surfaces, and their reflectance can be reversibly modulated from the visible to the near-infrared regions of the electromagnetic spectrum with both chemical and mechanical stimuli. Thus, we can endow common objects with any shape or form factor with tunable camouflage capabilities. Our work represents a key step toward the development of wearable biomimetic color and shapeshifting technologies for stealth applications.
A graphene solution for microwave interference
Microwave communication is ubiquitous in the modern world, with electromagnetic waves in the tens of gigahertz range providing efficient transmission with wide bandwidth for data links between Earth-orbiting satellites and ground stations. Such ultra-high frequency wireless communication is now so common, with a resultant crowding of the spectral bands allocated to different communications channels, that interference and electromagnetic compatibility (EMC) are serious concerns. Rules governing EMC dictate that new equipment meet stringent requirements concerning microwave shielding of both components and systems. This is driving a search for new materials to be used as coating layers, shields and filters in future nanoelectronic devices. Shielding electronic devices with a barrier that simply reflects incoming microwave radiation only shifts the electromagnetic pollution problem elsewhere. The research focus is therefore on developing EMC coatings that absorb rather than reflect microwaves, with a practical emphasis on layers less than a thousandth of a millimetre thick. A team of physicists led by Philippe Lambin from the Université de Namur in Belgium has found that a graphene plane can provide an effective absorbent shield against microwaves. The results of the study, the principal contributors to which are Konstantin Batrakov and Polina Kuzhir, both from the Belarussian State University in Minsk, are published in the journal ("Flexible transparent graphene/polymer multilayers for efficient electromagnetic field absorption"). All eight of the authors are part of the Graphene Flagship, a consortium of academic and industrial partners that focuses on the need for Europe to address the big scientific and technological challenges through long-term, multidisciplinary research efforts. 
Graphene-PMMA heterostructure. (click on image to enlarge) Lambin and his colleagues demonstrated that the conductivity of several graphene layers adds arithmetically when thin polymer spacers separate them. Maximum microwave absorption in the Ka communications band between 26.5 and 40 GHz is achieved with six graphene planes separated by layers of poly-methyl methacrylate (PMMA), a transparent plastic also known as acrylic glass. Multilayer microwave barriers constructed by researchers based at Joensuu University in Finland start with a first graphene layer deposited on a copper foil substrate by chemical vapour deposition. This layer is then covered with a 600-800 nanometre PMMA spacer obtained by spin coating, following which the copper is etched away with ferric chloride, and the graphene/PMMA heterostructure transferred to a quartz substrate. The procedure is repeated until the required number of graphene layers is reached. A single layer of graphene can absorb up to 25% of incident microwave radiation, which is a lot for a one atom-thick material. With a multilayer graphene/PMMA arrangement, the absorption rises to 50%. This can be understood by analysing the transmission and reflection of a plane wave at the interface between two dielectric media, when the interface contains an infinitesimally thin conducting layer. In this way, the researchers were able to optimise their graphene-PMMA structures for maximum absorption, with the results confirmed by rigorous electromagnetic testing. Moreover, notes Lambin, there is the interface between the shielding material and air to consider... “We have found that the static conductivity of graphene is close to the value which relates the magnetic and electric fields in any electromagnetic radiation propagating in air. Thanks to this happy coincidence, graphene is an ideal material for absorbing radio waves, thus protecting sensitive electronic devices.” The idea of using graphene/dielectric multilayers for electromagnetic wave absorption is not new. For example, a few years ago there was published a theoretical proposal for an ultra-broadband absorbing multilayer operating in the terahertz region, far higher than the Ka communications band discussed here. A multilayer terahertz shield would be a complex affair, with its graphene planes patterned at the micron scale in order to generate surface plasmon resonances – oscillations in the electrons which propagate along the interfaces between different material layers. The microwave barrier devised by the Graphene Flagship team is relatively simple by comparison, with advantages in terms of fabrication and scalability. In real-world applications, graphene/PMMA multilayers require protection against external chemical and mechanical agents. The quartz substrate should therefore face outwards, and be combined with a softer material. The choice and thickness of over-layer material used are additional parameters that will influence the microwave absorbance. Process scalability will increase considerably if stacks of few-layer graphene are deposited in one step, instead of piling up graphene monolayers with their PMMA shuttles. In addition, any process that raises the conductivity of graphene will reduce the number of atomic planes required to maximise the level of microwave absorption.
Graphene-PMMA heterostructure. (click on image to enlarge) Lambin and his colleagues demonstrated that the conductivity of several graphene layers adds arithmetically when thin polymer spacers separate them. Maximum microwave absorption in the Ka communications band between 26.5 and 40 GHz is achieved with six graphene planes separated by layers of poly-methyl methacrylate (PMMA), a transparent plastic also known as acrylic glass. Multilayer microwave barriers constructed by researchers based at Joensuu University in Finland start with a first graphene layer deposited on a copper foil substrate by chemical vapour deposition. This layer is then covered with a 600-800 nanometre PMMA spacer obtained by spin coating, following which the copper is etched away with ferric chloride, and the graphene/PMMA heterostructure transferred to a quartz substrate. The procedure is repeated until the required number of graphene layers is reached. A single layer of graphene can absorb up to 25% of incident microwave radiation, which is a lot for a one atom-thick material. With a multilayer graphene/PMMA arrangement, the absorption rises to 50%. This can be understood by analysing the transmission and reflection of a plane wave at the interface between two dielectric media, when the interface contains an infinitesimally thin conducting layer. In this way, the researchers were able to optimise their graphene-PMMA structures for maximum absorption, with the results confirmed by rigorous electromagnetic testing. Moreover, notes Lambin, there is the interface between the shielding material and air to consider... “We have found that the static conductivity of graphene is close to the value which relates the magnetic and electric fields in any electromagnetic radiation propagating in air. Thanks to this happy coincidence, graphene is an ideal material for absorbing radio waves, thus protecting sensitive electronic devices.” The idea of using graphene/dielectric multilayers for electromagnetic wave absorption is not new. For example, a few years ago there was published a theoretical proposal for an ultra-broadband absorbing multilayer operating in the terahertz region, far higher than the Ka communications band discussed here. A multilayer terahertz shield would be a complex affair, with its graphene planes patterned at the micron scale in order to generate surface plasmon resonances – oscillations in the electrons which propagate along the interfaces between different material layers. The microwave barrier devised by the Graphene Flagship team is relatively simple by comparison, with advantages in terms of fabrication and scalability. In real-world applications, graphene/PMMA multilayers require protection against external chemical and mechanical agents. The quartz substrate should therefore face outwards, and be combined with a softer material. The choice and thickness of over-layer material used are additional parameters that will influence the microwave absorbance. Process scalability will increase considerably if stacks of few-layer graphene are deposited in one step, instead of piling up graphene monolayers with their PMMA shuttles. In addition, any process that raises the conductivity of graphene will reduce the number of atomic planes required to maximise the level of microwave absorption.Graphene applications in mobile communication
GSM, UMTS, LTE, WiFi, Bluetooth – to name just a few of the wireless standards that have become a natural part of mobile communication today. For all these wireless standards, signal processing could not be done without the filtering of frequencies. Micro-acoustic piezoelectric resonators are the dominant technology in the market for this purpose. Theory predicts excellent oscillation characteristics for these resonators, if the electrode used for the excitation of the oscillation becomes very light. And the lightest conceivable electrode is electrically conductive graphene. "The metal electrodes, commonly used today, dampen the oscillation of the resonators through their mass – similar to the felt cover on a piano string – and therefore reduce the precision of signal separation in bandpass filters. While the metal electrodes cannot be arbitrarily thinned to reduce their mass and thus their damping, graphene still remains conductive even as an atomically thin electrode.", explains Dr. René Hoffmann, head of graphene research at Fraunhofer IAF. With such thin graphene electrodes, the mechanical quality factors come close to the theoretical ideal. If the oscillation characteristics of the piezoelectric resonators can be successfully improved and if higher coupling factors are achieved, both the signal separation precision and the energy efficiency of the filters will increase. Here, the challenge at hand is to connect the nearly massless graphene electrodes with the currently used mobile communication components based on piezoelectric aluminum nitride. 
The new CVD-reactor for the deposition of graphene at Fraunhofer IAF. In future, a cost-efficient and simplified technology will make the deposition and the transfer of graphene onto aluminum-nitride-based bandpass filters possible. Industry compatible graphene deposition technologies As one of the partners in the "Graphene Flagship", the largest funding initiative in the history of the European Union, Fraunhofer IAF is working on the development of an efficient technology for graphene deposition and graphene transfer onto aluminum nitride. As surprising as it may be to be able to manufacture and process graphene as atomically thin material at all – it is just as difficult to do so on an industrial scale. Many of the possible applications of graphene have not yet been successful since the production of the material is still too complex. Hence, the development of economical manufacturing and processing technologies is essential for the use of the outstanding theoretical properties of graphene in practice. A promising approach for the realization of graphene deposition on substrate sizes typical for the semiconductor industry can be found in chemical vapor deposition. Here, a catalyst surface such as copper is heated to nearly 1000 °C until gas containing carbon is broken down on the hot surface and reorganized into graphene. In future, this method is supposed to be further developed into a technology compatible for industry applications, to directly integrate graphene into existing aluminum-niride-based bandpass filters.
The new CVD-reactor for the deposition of graphene at Fraunhofer IAF. In future, a cost-efficient and simplified technology will make the deposition and the transfer of graphene onto aluminum-nitride-based bandpass filters possible. Industry compatible graphene deposition technologies As one of the partners in the "Graphene Flagship", the largest funding initiative in the history of the European Union, Fraunhofer IAF is working on the development of an efficient technology for graphene deposition and graphene transfer onto aluminum nitride. As surprising as it may be to be able to manufacture and process graphene as atomically thin material at all – it is just as difficult to do so on an industrial scale. Many of the possible applications of graphene have not yet been successful since the production of the material is still too complex. Hence, the development of economical manufacturing and processing technologies is essential for the use of the outstanding theoretical properties of graphene in practice. A promising approach for the realization of graphene deposition on substrate sizes typical for the semiconductor industry can be found in chemical vapor deposition. Here, a catalyst surface such as copper is heated to nearly 1000 °C until gas containing carbon is broken down on the hot surface and reorganized into graphene. In future, this method is supposed to be further developed into a technology compatible for industry applications, to directly integrate graphene into existing aluminum-niride-based bandpass filters.New processing technology converts packing peanuts to battery components
Researchers have shown how to convert waste packing peanuts into high-performance carbon electrodes for rechargeable lithium-ion batteries that outperform conventional graphite electrodes, representing an environmentally friendly approach to reuse the waste. Batteries have two electrodes, called an anode and a cathode. The anodes in most of today's lithium-ion batteries are made of graphite. Lithium ions are contained in a liquid called an electrolyte, and these ions are stored in the anode during recharging. Now, researchers at Purdue University have shown how to manufacture carbon-nanoparticle and microsheet anodes from polystyrene and starch-based packing peanuts, respectively. 
This schematic depicts a process for converting waste packing peanuts into high-performance carbon electrodes for rechargeable lithium-ion batteries that outperform conventional graphite electrodes, representing an environmentally friendly approach to reuse the waste. (Purdue University image/Vinodkumar Etacheri) "We were getting a lot of packing peanuts while setting up our new lab," recalled postdoctoral research associate Vinodkumar Etacheri. "Professor Vilas Pol suggested a pathway to do something useful with these peanuts." This simple suggestion led to a potential new eco-friendly application for the packaging waste. Research findings indicate that the new anodes can charge faster and deliver higher "specific capacity" compared to commercially available graphite anodes, Pol said. The new findings are being presented during the 249th American Chemical Society National Meeting & Exposition in Denver on March 22-26. The work was performed by Etacheri, Pol and undergraduate chemical engineering student Chulgi Nathan Hong. "Although packing peanuts are used worldwide as a perfect solution for shipping, they are notoriously difficult to break down, and only about 10 percent are recycled," Pol said. "Due to their low density, huge containers are required for transportation and shipment to a recycler, which is expensive and does not provide much profit on investment." Consequently, packing peanuts often end up in landfills, where they remain intact for decades. Although the starch-based versions are more environmentally friendly than the polystyrene peanuts, they do contain chemicals and detergents that can contaminate soil and aquatic ecosystems, posing a threat to marine animals, he said. The new method "is a very simple, straightforward approach," Pol said. "Typically, the peanuts are heated between 500 and 900 degrees Celsius in a furnace under inert atmosphere in the presence or absence of a transition metal salt catalyst." The resulting material is then processed into the anodes. "The process is inexpensive, environmentally benign and potentially practical for large-scale manufacturing," Etacheri said. "Microscopic and spectroscopic analyses proved the microstructures and morphologies responsible for superior electrochemical performances are preserved after many charge-discharge cycles." Commercial anode particles are about 10 times thicker than the new anodes and have higher electrical resistance, which increase charging time. "In our case, if we are lithiating this material during the charging of a battery it has to travel only 1 micrometer distance, so you can charge and discharge a battery faster than your commercially available material," Pol said. Because the sheets are thin and porous, they allow better contact with the liquid electrolyte in batteries. "These electrodes exhibited notably higher lithium-ion storage performance compared to the commercially available graphite anodes," he said. Packing-peanut-derived carbon anodes demonstrated a maximum specific capacity of 420 mAh/g (milliamp hours per gram), which is higher than the theoretical capacity of graphite (372 mAh/g), Etacheri said. "Long-term electrochemical performances of these carbon electrodes are very stable," he said. "We cycled it 300 times without significant capacity loss. These carbonaceous electrodes are also promising for rechargeable sodium-ion batteries. Future work will include steps to potentially improve performance by further activation to increase the surface area and pore size to improve the electrochemical performance." Abstract "Upcycling of Packing-Peanuts into Carbon Microsheet Anodes for Lithium-Ion Batteries". Vinodkumar Etacheri, Chulgi Nathan Hong, and Vilas G. Pol; School of Chemical Engineering, Purdue University Environmental pollution caused by ubiquitous waste packaging materials is a serious global issue that needs to be urgently addressed. Millions of tons of plastic waste are generated worldwide every year, and it is critical to find efficient methods for their disposal and recycling. Recent studies verified that plastic containers, bags, bottles and packing peanuts constitute 31 % of the municipal waste created in the U. S. A, and only ~ 40 % of these packaging materials are recycled. Currently, only a very small fraction (~10 %) of the packing peanuts is being recycled. Due to their low density (huge containers are required for transportation), shipment to a recycler is expensive, and does not provide profit on investment. As a result, most often packing peanuts end up in landfills, where they stay intact for generations. Chemical moieties such as heavy metals, chlorides, phthalates etc. present in the packing peanuts can be easily leached into the surrounding media and deteriorate soil/water quality. We addressed the detrimental environmental impacts caused by polystyrene and starch based packing peanuts by upcycling them to carbon nanoparticles and microsheets, respectively for electrochemical energy storage, especially Li, and Na-ion batteries. State of the art synthesis of carbonaceous materials often involves the use of hydrocarbon precursors such as acetylene or coal. The method described herein does not use pressurized containers, which makes them attractive for the large-scale production of carbonaceous materials for numerous applications. Anodes composed of these microsheets and nanoparticles outperformed the electrochemical properties of commercial carbon anode in Li, and Na-ion batteries. At a current density of 0.1 C, carbon microsheet, and nanoparticle anodes exhibited Li-ion storage specific capacity of 420 mAh/g, which is even superior to the theoretical capacity of graphite (372 mAh/g). Superior electrochemical properties of the carbon electrodes are attributed to their disordered nature, and porous microstructure, which allows improved solid-state and interfacial Li, and Na-ion diffusion kinetics. The synthetic method demonstrated here is inexpensive, environmentally benign, and scalable method for the synthesis of carbonaceous materials for electrochemical energy storage.
This schematic depicts a process for converting waste packing peanuts into high-performance carbon electrodes for rechargeable lithium-ion batteries that outperform conventional graphite electrodes, representing an environmentally friendly approach to reuse the waste. (Purdue University image/Vinodkumar Etacheri) "We were getting a lot of packing peanuts while setting up our new lab," recalled postdoctoral research associate Vinodkumar Etacheri. "Professor Vilas Pol suggested a pathway to do something useful with these peanuts." This simple suggestion led to a potential new eco-friendly application for the packaging waste. Research findings indicate that the new anodes can charge faster and deliver higher "specific capacity" compared to commercially available graphite anodes, Pol said. The new findings are being presented during the 249th American Chemical Society National Meeting & Exposition in Denver on March 22-26. The work was performed by Etacheri, Pol and undergraduate chemical engineering student Chulgi Nathan Hong. "Although packing peanuts are used worldwide as a perfect solution for shipping, they are notoriously difficult to break down, and only about 10 percent are recycled," Pol said. "Due to their low density, huge containers are required for transportation and shipment to a recycler, which is expensive and does not provide much profit on investment." Consequently, packing peanuts often end up in landfills, where they remain intact for decades. Although the starch-based versions are more environmentally friendly than the polystyrene peanuts, they do contain chemicals and detergents that can contaminate soil and aquatic ecosystems, posing a threat to marine animals, he said. The new method "is a very simple, straightforward approach," Pol said. "Typically, the peanuts are heated between 500 and 900 degrees Celsius in a furnace under inert atmosphere in the presence or absence of a transition metal salt catalyst." The resulting material is then processed into the anodes. "The process is inexpensive, environmentally benign and potentially practical for large-scale manufacturing," Etacheri said. "Microscopic and spectroscopic analyses proved the microstructures and morphologies responsible for superior electrochemical performances are preserved after many charge-discharge cycles." Commercial anode particles are about 10 times thicker than the new anodes and have higher electrical resistance, which increase charging time. "In our case, if we are lithiating this material during the charging of a battery it has to travel only 1 micrometer distance, so you can charge and discharge a battery faster than your commercially available material," Pol said. Because the sheets are thin and porous, they allow better contact with the liquid electrolyte in batteries. "These electrodes exhibited notably higher lithium-ion storage performance compared to the commercially available graphite anodes," he said. Packing-peanut-derived carbon anodes demonstrated a maximum specific capacity of 420 mAh/g (milliamp hours per gram), which is higher than the theoretical capacity of graphite (372 mAh/g), Etacheri said. "Long-term electrochemical performances of these carbon electrodes are very stable," he said. "We cycled it 300 times without significant capacity loss. These carbonaceous electrodes are also promising for rechargeable sodium-ion batteries. Future work will include steps to potentially improve performance by further activation to increase the surface area and pore size to improve the electrochemical performance." Abstract "Upcycling of Packing-Peanuts into Carbon Microsheet Anodes for Lithium-Ion Batteries". Vinodkumar Etacheri, Chulgi Nathan Hong, and Vilas G. Pol; School of Chemical Engineering, Purdue University Environmental pollution caused by ubiquitous waste packaging materials is a serious global issue that needs to be urgently addressed. Millions of tons of plastic waste are generated worldwide every year, and it is critical to find efficient methods for their disposal and recycling. Recent studies verified that plastic containers, bags, bottles and packing peanuts constitute 31 % of the municipal waste created in the U. S. A, and only ~ 40 % of these packaging materials are recycled. Currently, only a very small fraction (~10 %) of the packing peanuts is being recycled. Due to their low density (huge containers are required for transportation), shipment to a recycler is expensive, and does not provide profit on investment. As a result, most often packing peanuts end up in landfills, where they stay intact for generations. Chemical moieties such as heavy metals, chlorides, phthalates etc. present in the packing peanuts can be easily leached into the surrounding media and deteriorate soil/water quality. We addressed the detrimental environmental impacts caused by polystyrene and starch based packing peanuts by upcycling them to carbon nanoparticles and microsheets, respectively for electrochemical energy storage, especially Li, and Na-ion batteries. State of the art synthesis of carbonaceous materials often involves the use of hydrocarbon precursors such as acetylene or coal. The method described herein does not use pressurized containers, which makes them attractive for the large-scale production of carbonaceous materials for numerous applications. Anodes composed of these microsheets and nanoparticles outperformed the electrochemical properties of commercial carbon anode in Li, and Na-ion batteries. At a current density of 0.1 C, carbon microsheet, and nanoparticle anodes exhibited Li-ion storage specific capacity of 420 mAh/g, which is even superior to the theoretical capacity of graphite (372 mAh/g). Superior electrochemical properties of the carbon electrodes are attributed to their disordered nature, and porous microstructure, which allows improved solid-state and interfacial Li, and Na-ion diffusion kinetics. The synthetic method demonstrated here is inexpensive, environmentally benign, and scalable method for the synthesis of carbonaceous materials for electrochemical energy storage.New transitory form of silica observed
A Carnegie-led team was able to discover five new forms of silica under extreme pressures at room temperature. Their findings are published by . 
A simulated visual representation of the structural transition from coesite to post-stishovite. The silicon atoms (blue spheres) surrounded by four oxygen atoms (red spheres) are shown as blue tetrahedrons. The silicon atoms surrounded by six oxygen atoms are shown as green octahedrons. The intermediate phases are not filled in with color, showing the four stages that are neither all-blue like coesite nor all-green like post-stishovite. This image is provided courtesy of Ho-Kwang Mao. (Image: Ho-Kwang Mao) Silicon dioxide, commonly called silica, is one of the most-abundant natural compounds and a major component of the Earth's crust and mantle. It is well-known even to non-scientists in its quartz crystalline form, which is a major component of sand in many places. It is used in the manufacture of microchips, cement, glass, and even some toothpaste. Silica's various high-pressure forms make it an often-used study subject for scientists interested in the transition between different chemical phases under extreme conditions, such as those mimicking the deep Earth. The first-discovered high-pressure, high-temperature denser form, or phase, of silica is called coesite, which, like quartz, consists of building blocks of silicon atoms surrounded by four oxygen atoms. Under greater pressures and temperatures, it transforms into an even denser form called stishovite, with silicon atoms surrounded by six oxygen atoms. The transition between these phases was crucial for learning about the pressure gradient of the deep Earth and the four-to-six configuration shift has been of great interest to geoscientists. Experiments have revealed even higher-pressure phases of silica beyond these two, sometimes called post-stishovite. A chemical phase is a distinctive and uniform configuration of the molecules that make up a substance. Changes in external conditions, such as temperature and pressure, can induce a transition from one phase to another, not unlike water freezing into ice or boiling into steam. The team, including Carnegie's Qingyang Hu, Jinfu Shu, Yue Meng, Wenge Yang, and Ho-Kwang, "Dave" Mao, demonstrated that under a range from 257,000 to 523,000 times normal atmospheric pressure (26 to 53 gigapascals), a single crystal of coesite transforms into four new, co-existing crystalline phases before finally recombining into a single phase that is denser than stishovite, sometimes called post-stishovite, which is the team's fifth newly discovered phase. This transition takes place at room temperature, rather than the extreme temperatures found deep in the earth. Scientists previously thought that this intermediate was amorphous, meaning that it lacked the long-range order of a crystalline structure. This new study uses superior x-ray analytical probes to show otherwise--they are four, distinct, well-crystalized phases of silica without amorphization. Advanced theoretical calculations performed by the team provided detailed explanations of the transition paths from coesite to the four crystalline phases to post-stishovite. "Scientists have long debated whether a phase exists between the four- and six-oxygen phases," Mao said. "These newly discovered four transition phases and the new phase of post-stishovite we discovered show the missing link for which we've been searching."
A simulated visual representation of the structural transition from coesite to post-stishovite. The silicon atoms (blue spheres) surrounded by four oxygen atoms (red spheres) are shown as blue tetrahedrons. The silicon atoms surrounded by six oxygen atoms are shown as green octahedrons. The intermediate phases are not filled in with color, showing the four stages that are neither all-blue like coesite nor all-green like post-stishovite. This image is provided courtesy of Ho-Kwang Mao. (Image: Ho-Kwang Mao) Silicon dioxide, commonly called silica, is one of the most-abundant natural compounds and a major component of the Earth's crust and mantle. It is well-known even to non-scientists in its quartz crystalline form, which is a major component of sand in many places. It is used in the manufacture of microchips, cement, glass, and even some toothpaste. Silica's various high-pressure forms make it an often-used study subject for scientists interested in the transition between different chemical phases under extreme conditions, such as those mimicking the deep Earth. The first-discovered high-pressure, high-temperature denser form, or phase, of silica is called coesite, which, like quartz, consists of building blocks of silicon atoms surrounded by four oxygen atoms. Under greater pressures and temperatures, it transforms into an even denser form called stishovite, with silicon atoms surrounded by six oxygen atoms. The transition between these phases was crucial for learning about the pressure gradient of the deep Earth and the four-to-six configuration shift has been of great interest to geoscientists. Experiments have revealed even higher-pressure phases of silica beyond these two, sometimes called post-stishovite. A chemical phase is a distinctive and uniform configuration of the molecules that make up a substance. Changes in external conditions, such as temperature and pressure, can induce a transition from one phase to another, not unlike water freezing into ice or boiling into steam. The team, including Carnegie's Qingyang Hu, Jinfu Shu, Yue Meng, Wenge Yang, and Ho-Kwang, "Dave" Mao, demonstrated that under a range from 257,000 to 523,000 times normal atmospheric pressure (26 to 53 gigapascals), a single crystal of coesite transforms into four new, co-existing crystalline phases before finally recombining into a single phase that is denser than stishovite, sometimes called post-stishovite, which is the team's fifth newly discovered phase. This transition takes place at room temperature, rather than the extreme temperatures found deep in the earth. Scientists previously thought that this intermediate was amorphous, meaning that it lacked the long-range order of a crystalline structure. This new study uses superior x-ray analytical probes to show otherwise--they are four, distinct, well-crystalized phases of silica without amorphization. Advanced theoretical calculations performed by the team provided detailed explanations of the transition paths from coesite to the four crystalline phases to post-stishovite. "Scientists have long debated whether a phase exists between the four- and six-oxygen phases," Mao said. "These newly discovered four transition phases and the new phase of post-stishovite we discovered show the missing link for which we've been searching."
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