MIT: Porous, 3-D forms of graphene developed at MIT can be 10 times as strong as steel but much lighter


mit-stronger-graph-586fc75e37984A three-dimensional graphene assembly and scanning electron microscope image of a graphene assembly (insert, scale bar, 20 µm). Credit: Qin et al. Sci. Adv. 2017;3:e1601536

A team of researchers at MIT has designed one of the strongest lightweight materials known, by compressing and fusing flakes of graphene, a two-dimensional form of carbon. The new material, a sponge-like configuration with a density of just 5 percent, can have a strength 10 times that of steel.

In its two-dimensional form, is thought to be the strongest of all known materials. But researchers until now have had a hard time translating that two-dimensional strength into useful three-dimensional materials.

The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.

The findings are being reported today in the journal Science Advances, in a paper by Markus Buehler, the head of MIT’s Department of Civil and Environmental Engineering (CEE) and the McAfee Professor of Engineering; Zhao Qin, a CEE research scientist; Gang Seob Jung, a graduate student; and Min Jeong Kang MEng ’16, a recent graduate.

Other groups had suggested the possibility of such lightweight structures, but lab experiments so far had failed to match predictions, with some results exhibiting several orders of magnitude less strength than expected. The MIT team decided to solve the mystery by analyzing the material’s behavior down to the level of individual atoms within the structure. They were able to produce a mathematical framework that very closely matches experimental observations.

Researchers design one of strongest, lightest materials known
The closely packed graphene-inclusion structure obtained after cyclic equilibrations. Credit:Qin et al. Sci. Adv. 2017;3:e1601536

Two-dimensional materials—basically flat sheets that are just one atom in thickness but can be indefinitely large in the other dimensions—have exceptional strength as well as unique electrical properties. But because of their extraordinary thinness, “they are not very useful for making 3-D materials that could be used in vehicles, buildings, or devices,” Buehler says. “What we’ve done is to realize the wish of translating these 2-D materials into three-dimensional structures.”

The team was able to compress small flakes of graphene using a combination of heat and pressure. This process produced a strong, stable structure whose form resembles that of some corals and microscopic creatures called diatoms. These shapes, which have an enormous surface area in proportion to their volume, proved to be remarkably strong. “Once we created these 3-D structures, we wanted to see what’s the limit—what’s the strongest possible material we can produce,” says Qin. To do that, they created a variety of 3-D models and then subjected them to various tests. In computational simulations, which mimic the loading conditions in the tensile and compression tests performed in a tensile loading machine, “one of our samples has 5 percent the density of steel, but 10 times the strength,” Qin says.

Buehler says that what happens to their 3-D graphene material, which is composed of curved surfaces under deformation, resembles what would happen with sheets of paper. Paper has little strength along its length and width, and can be easily crumpled up. But when made into certain shapes, for example rolled into a tube, suddenly the strength along the length of the tube is much greater and can support substantial weight. Similarly, the geometric arrangement of the graphene flakes after treatment naturally forms a very strong configuration.

The new configurations have been made in the lab using a high-resolution, multimaterial 3-D printer. They were mechanically tested for their tensile and compressive properties, and their mechanical response under loading was simulated using the team’s theoretical models. The results from the experiments and simulations matched accurately.

Researchers design one of strongest, lightest materials known
Tensile and compressive tests on the printed sample. Credit: Qin et al. Sci. Adv. 2017;3:e1601536

The new, more accurate results, based on atomistic computational modeling by the MIT team, ruled out a possibility proposed previously by other teams: that it might be possible to make 3-D graphene structures so lightweight that they would actually be lighter than air, and could be used as a durable replacement for helium in balloons. The current work shows, however, that at such low densities, the material would not have sufficient strength and would collapse from the surrounding air pressure.

But many other possible applications of the material could eventually be feasible, the researchers say, for uses that require a combination of extreme strength and light weight. “You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” Buehler says, to gain similar advantages of strength combined with advantages in cost, processing methods, or other material properties (such as transparency or electrical conductivity).

“You can replace the material itself with anything,” Buehler says. “The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”

The unusual geometric shapes that graphene naturally forms under heat and pressure look something like a Nerf ball—round, but full of holes. These shapes, known as gyroids, are so complex that “actually making them using conventional manufacturing methods is probably impossible,” Buehler says. The team used 3-D-printed models of the structure, enlarged to thousands of times their natural size, for testing purposes.

Researchers design one of strongest, lightest materials known
Model of gyroid graphene with 20 nm length constant. Credit: Qin et al. Sci. Adv. 2017;3:e1601536

For actual synthesis, the researchers say, one possibility is to use the polymer or metal particles as templates, coat them with graphene by chemical vapor deposit before heat and pressure treatments, and then chemically or physically remove the polymer or metal phases to leave 3-D graphene in the gyroid form. For this, the computational model given in the current study provides a guideline to evaluate the mechanical quality of the synthesis output.

The same geometry could even be applied to large-scale structural materials, they suggest. For example, concrete for a structure such a bridge might be made with this porous geometry, providing comparable with a fraction of the weight. This approach would have the additional benefit of providing good insulation because of the large amount of enclosed airspace within it.

Because the shape is riddled with very tiny pore spaces, the material might also find application in some filtration systems, for either water or chemical processing. The mathematical descriptions derived by this group could facilitate the development of a variety of applications, the researchers say.

Explore further: New study shows nickel graphene can be tuned for optimal fracture strength

More information: “The mechanics and design of a lightweight three-dimensional graphene assembly,” Science Advances, DOI: 10.1126/sciadv.1601536 , advances.sciencemag.org/content/3/1/e1601536

 

3-D printing and nanotechnology, a mighty alliance to detect toxic liquids


3dprintinganAs soon as it comes out of the printing nozzle, the solvent evaporates and the ink solidifies. It takes the form of filaments slightly bigger than a hair. The manufacturing work can then begin. Credit: Polytechnique Montréal

Carbon nanotubes have made headlines in scientific journals for a long time, as has 3D printing. But when both combine with the right polymer, in this case a thermoplastic, something special occurs: electrical conductivity increases and makes it possible to monitor liquids in real time. This is a huge success for Polytechnique Montréal.

The article “3D Printing of Highly Conductive Nanocomposites for the Functional Optimization of Liquid Sensors” was published in the journal Small. Renowned in the field of micro- and nanotechnology, Small placed this article on its back cover, a sure sign of the relevance of the research conducted by mechanical engineer Professor Daniel Therriault and his team. In practical terms, the result of this research looks like a cloth; but as soon as a liquid comes into contact with it, said cloth is able to identify its nature. In this case, it is ethanol, but it might have been another liquid. Such a process would be a terrific advantage to heavy industry, which uses countless toxic liquids.

A simple yet efficient recipe

While deceptively simple, the recipe is so efficient that Professor Therriault protected it with a patent. In fact, a U.S. company is already looking at commercializing this material printable in 3D, which is highly conductive and has various potential applications.

The first step: take a thermoplastic and, with a solvent, transform it into a solution so that it becomes a liquid. Second step: as a result of the porousness of this thermoplastic solution, carbon nanotubes can be incorporated into it like never before, somewhat like adding sugar into a cake mix. The result: a kind of black ink that’s fairly viscous and whose very high conductivity approximates that of some metals. Third step: this black ink, which is in fact a nanocomposite, can now move on to 3D printing. As soon as it comes out of the printing nozzle, the solvent evaporates and the ink solidifies. It takes the form of filaments slightly bigger than a hair. The manufacturing work can then begin.

3-D printing and nanotechnology, a mighty alliance to detect toxic liquids
Credit: Polytechnique Montréal

The advantages of this technology

The research conducted at Polytechnique Montréal is at the vanguard in the field of uses for 3D printers. The era of amateurish prototyping, like printing little plastic objects, belongs to the past. These days, all manufacturing industries, whether aviation, aerospace, robotics or medicine, etc., have set their sights on this technology.

There are several reasons for this. Firstly, the lightness of parts because plastic is substituted for metal. Then there is the precision of the work done at the microscopic level, as is the case here. Lastly, with the nanocomposite filaments usable at room temperature, conductivities can be obtained that approximate those of some metals. Better still, since the geometry of filaments can be varied, measures can be calibrated that make it possible to read the various electric signatures of liquids that are to be monitored.

A topical example: pipelines

At the connection points of pipes that form pipelines, there are flanges. The idea would be to factory- manufacture the pipes with flanges coated by 3D printing. The coating would be a nanocomposite whose electric signature is calibrated according to the liquid being transported – oil, for instance. If there is a leak and the liquid touches the printed sensors based on the concept developed by Professor Therriault and his team, an alert would sound in record time, and in a very targeted way. That’s a tremendous advantage, both for the population and the environment; in case of a leak, the faster the reaction time, the lesser the damages.

Explore further: Chinese scientists unveil liquid phase 3-D printing method using low melting metal alloy ink

More information: Kambiz Chizari et al, Liquid Materials: 3D Printing of Highly Conductive Nanocomposites for the Functional Optimization of Liquid Sensors, Small (2016). DOI: 10.1002/smll.201670232

 

Semiconductor eyed for next-generation ‘power electronics’: Beta Gallium Oxide


semiconductoThe schematic at left shows the design for an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft. At …more

Researchers have demonstrated the high-performance potential of an experimental transistor made of a semiconductor called beta gallium oxide, which could bring new ultra-efficient switches for applications such as the power grid, military ships and aircraft.

The semiconductor is promising for next-generation “power electronics,” or devices needed to control the flow of electrical energy in circuits. Such a technology could help to reduce global energy use and by replacing less efficient and bulky power electronics switches now in use.

The transistor, called a gallium oxide on insulator , or GOOI, is especially promising because it possesses an “ultra-wide bandgap,” a trait needed for switches in high-voltage applications.

Compared to other semiconductors thought to be promising for the transistors, devices made from beta gallium oxide have a higher “breakdown voltage,” or the voltage at which the device fails, said Peide Ye, Purdue University’s Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering.

Findings are detailed in a research paper published this month in IEEE Electron Device Letters. Graduate student Hong Zhou performed much of the research.

The team also developed a new low-cost method using adhesive tape to peel off layers of the semiconductor from a single crystal, representing a far less expensive alternative to a laboratory technique called epitaxy. The market price for a 1-centimeter-by-1.5-centimeter piece of beta gallium oxide produced using epitaxy is about $6,000. In comparison, the “Scotch-tape” approach costs pennies and it can be used to cut films of the beta material into belts or “nano-membranes,” which can then be transferred to a conventional silicon disc and manufactured into devices, Ye said.

The technique was found to yield extremely smooth films, having a surface roughness of 0.3 nanometers, which is another factor that bodes well for its use in electronic devices, said Ye, who is affiliated with the NEPTUNE Center for Power and Energy Research, funded by the U.S. Office of Naval Research and based at Purdue’s Discovery Park. Related research was supported by the center.

The Purdue team achieved electrical currents 10 to 100 times greater than other research groups working with the semiconductor, Ye said.

One drawback to the material is that it possesses poor thermal properties. To help solve the problem, future research may include work to attach the material to a substrate of diamond or aluminum nitride.

Explore further: Transistors and diodes made from advanced semiconductor materials could perform much better than silicon

More information: High Performance Depletion/Enhancement-Mode β-Ga2O3 on Insulator (GOOI) Field-effect Transistors with Record Drain Currents of 600/450 mA/mm, IEEE Electron Device Letters, 2017.

 

PNNL ~ One-pot technique creates structures with more efficient energy storage and manufacturing


one-pot-588a732e171b4Highly ordered sodium silicate particles (bottom right) with a regular array of spherical pores (bottom left) form on silicon surface. The one-step synthesis is directed by the atomic ordering of the substrate, which induces the formation …more

To create more efficient catalysts, sensing and separation membrane, and energy storage devices, scientists often start with particles containing tiny pore channels. Defects between the particles can hamper performance. At Pacific Northwest National Laboratory, a team created a one-pot method that produces complex, well-structured microscopic pyramids. This approach offers control over three-dimensional material growth similar to that seen in nature, a vital benchmark for material synthesis.

“It’s relatively easy to grow thin layers of material,” said Dr. Maria Sushko, a PNNL materials scientist who worked on the study. “Now, we can grow supported three-dimensional crystals that have a larger ordered structure on the inside as well—a crystal within a crystal.”

Energy storage materials that are more efficient could the way we use renewable energy. More efficient catalysts, sensors, and separators that last longer and work harder could reduce the energy demands and waste from manufacturing plants and refineries. These technologies require innovative materials, and the team’s technique offers a new way to create them. Now, scientists can grow well-defined three-dimensional structures on a surface in a single step. Growing a material directly on the surface eliminates steps in testing new ideas for electrodes or catalysts.

In the simplest terms, the team’s approach takes advantage of a relationship among the atomic ordering of a silicon substrate, structure of organic template, and atomic structure of sodium silicate. When organic molecules and a sodium silicate precursor are combined in the right proportions and the solution is heated in the presence of the silicon surface, the directs the template’s self-assembly along a specific crystallographic direction. The template directs the formation of sodium silicate along the same crystallographic direction of the substrate, ensuring near-perfect lattice matching between silicon and sodium silicate.

After a series of transformations, the organic template forms an array of well-defined spherical micelles several nanometers in diameter. The micelles are arranged in a cubic lattice and encapsulated into sodium silicate. The result is an array of oriented ordered porous pyramids with a well-defined cubic lattice of pores, confirmed by electron microscopes at the U.S. Department of Energy’s (DOE’s) EMSL, a scientific user facility.

In nature, proteins direct the growth of complex structures, such as shells, bone and tooth enamel. The team’s novel approach provides precise control over materials architecture similar to that seen in nature. The scientists can vary the structure and size of the particles. Their system makes different structures, with different sizes and compositions, as needed. This level of control in the laboratory is a significant benchmark for materials synthesis.

The team’s technique is an important addition to the methods of synthesizing supported three-dimensional structures. The team is exploring ways to expand this technique beyond to other materials.

Explore further: New insights into the forms of metal-organic frameworks

More information: Yongsoon Shin et al. Double Epitaxy as a Paradigm for Templated Growth of Highly Ordered Three-Dimensional Mesophase Crystals, ACS Nano (2016). DOI: 10.1021/acsnano.6b03999

 

Europe’s nanotechnology ‘Sunflower’ project to design and use less toxic photovoltaic materials (w/video)


Posted: Jan 27, 2017




The University Institute for Advanced Materials Research at the Universitat Jaume I (UJI) has participated in the European Project Sunflower, whose objective has been the development of organic photovoltaic materials less toxic and viable for industrial production. 

A consortium of 17 research and business institutions has carried out this European project in the field of nanotechnology for four years and with an overall budget of 14.2 million euros, with funding of 10.1 million euros from the Seventh Framework Programme of the European Commission.

An introduction to Sunflower

Researchers at Sunflower have carried out several studies, among the most successful of which there are the design of an organic photovoltaic cell that can be printed and, consequently, has great versatility. In short, “we can assure that, thanks to these works, progress has been made in the achievement of solar cells with a good performance, low cost and very interesting architectural characteristics”, states the director of the University Institute for Advanced Materials Research (INAM) Juan Bisquert.

The goals of Sunflower were very ambitious, according to Antonio Guerrero, researcher at the Department of Physics integrated in the INAM, since it was intended “not only to improve the stability and efficiency of the photovoltaic materials, but also to reduce their costs of production”. 

In fact, according to Guerrero, “the processes for making the leap from the laboratory to the industrial scale have been improved because, among others, non-halogenated solvents have been used that are compatible with industrial production methods and that considerably reduce the toxic loading of halogenates”.

“The involvement of our institute in these projects has a great interest because one of our priority lines of research is the new materials to develop renewable energies,” says Bisquert, who is also professor of Applied Physics. In addition, these consortia involve the work of academia and industry. According to the researcher, “the transfer of knowledge to society is favoured and, in this case, we demonstrate that organic materials investigated for twenty years are already close to become viable technologies”.

Change of use of plastic materials

The participation of UJI researchers at Sunflower has focused on “improving the aspect of chemical reactivity of materials or structural compatibility”, says Germà García, professor of Applied Physics and member of INAM. 

“We have worked to move from the concepts of inorganic electronics to photovoltaic cells to the part of organic electronics,” he adds. The researchers wanted to take advantage of the faculties of absorption and conduction of plastic materials and to verify its capacity of solar production, an unusual use because normally they are used as an electrical insulation.

At UJI laboratories, they have studied the organic materials, very complex devices because they have up to eight nanometric layers. “We have made advanced electrical measurements to see where the energy losses were and thus to inform producers of materials and devices in order to improve the stability and efficiency of solar cells,” explains Guerrero.

Solar energy in everyday objects

“The potential applications of organic photovoltaic technology (OPV) are numerous, ranging from mobile consumer electronics to architecture,” says the project coordinator Giovanni Nisato, from the Swiss Centre for Electronics and Microtechnology (CSEM). 

“Thanks to the results we have obtained, printed organic photovoltaics will become part of our daily lives, and will allow us to use renewable energy and respect the environment with a positive impact on our quality of life,” according to Nisato.

The European Sunflower project has been developed over 48 months with the main objective of extending the life and cost-efficiency of organic photovoltaic technology through better process control and understanding of materials. In addition, in the opinion of those responsible, the results of this research could double the share of renewable energy in its energy matrix, from 14% in 2012 to 27-30% by 2030. In fact, Sunflower has facilitated a significant increase in the use of solar energy incorporated in everyday objects.

The Sunflower consortium consists of 17 partners from across Europe: CSEM (Switzerland), DuPont Teijin Films UK Ltd (UK), Amcor Flexibles Kreuzlingen AG (Switzerland), Agfa-Gevaert NV (Belgium), Fluxim AG (Switzerland), University of Antwerp (Belgium), SAES Getters SpA (Italy), Consiglio Nazionale delle Ricerche-ISMN-Bologna (Italy), Hochschule für Life Sciences FHNW (Switzerland), Chalmers Tekniska Hoegskola AB (Sweden), Fraunhofer Institut der angewandten Forschung zur Foerderung @EV (Germany), Linköpings Universitet (Sweden), Universitat Jaume I (Spain), Genes’Ink (France), National Centre for Scientific Research (France), Belectric OPV GmbH (Germany) and Merck KGaA (Germany).

Meanwhile, the main lines of research at the INAM focus on new types of materials for clean energy devices, solar cells based on low cost compounds, such as perovskite and other organic compounds. Furthermore, INAM studies the production of fuels from sunlight, breaking water molecules and producing hydrogen and other catalytic materials in the chemical aspect, all of great importance in the context of international research.

Source: Ruvid

First steps towards photonic quantum network



Advanced nanostructures are well on their way to revolutionising quantum technology for quantum networks based on light. 

Researchers from the Niels Bohr Institute have now developed the first building blocks needed to construct complex quantum photonic circuits for quantum networks. This rapid development in quantum networks is highlighted in an article in the prestigious scientific journal, Nature (“Chiral quantum optics”).

Photon Gun




This is an illustration of a photon gun. A quantum dot (the yellow symbol) emits one photon (red wave packet) at a time. The quantum dot is embedded in a photonic crystal structure, which is obtained by etching holes (black circles) in a semiconductor material. Due to the holes, the photons cannot be emitted in all directions, but only along the waveguide, which is formed by omitting a number of holes (Image: Søren Stobbe, NBI)

Quantum technology based on light (photons) is called quantum photonics, while electronics is based on electrons. Photons (light particles) and electrons behave differently at the quantum level. A quantum entity is the smallest unit in the microscopic world. For example, photons are the fundamental constituent of light and electrons of electric current. 
Electrons are so-called fermions and can easily be isolated to conduct current one electron at a time.

In contrast photons are bosons, which prefer to bunch together. But since information for quantum communication based on photonics is encoded in a single photon, it is necessary to emit and send them one at a time.

Increased information capacity

Information based on photons has great advantages; photons interact only very weakly with the environment – unlike electrons, so photons do not lose much energy along the way and can therefore be sent over long distances. 
 are therefore very well suited for carrying and distributing information and a quantum network based on photons will be able to encode much more information than is possible with current computer technology and the information could not be intercepted en route.

Many research groups around the world are working intensively in this research field, which is developing rapidly and in fact the first commercial quantum photonics products are starting to be manufactured.

Control of the photons

“A prerequisite for quantum networks is the ability to create a stream of single photons on demand and the researchers at the Niels Bohr Institute succeeded in doing exactly that,” explains Peter Lodahl, professor and head of the Quantum Photonics research group at the Niels Bohr Institute, University of Copenhagen. “We have developed a photonic chip, which acts as a photon gun. The photonic chip consists of an extremely small crystal that is 10 microns wide and is 160 nanometres thick. Embedded in the middle of the chip is a light source, which is a so-called quantum dot.”

Illuminating the quantum dot with laser light excites an electron, which can then jump from one orbit to another and thereby emit a single photon at a time. Photons are usually emitted in all directions, but the photonic chip is designed so that all the photons are sent out through a photonic waveguide.

Directional Emission of Photons




This is a directional emission of photons. The figure shows the calculations of the photon emission in the new directional single-photon source. If the spin of the quantum dot’s electron points up, the photon will be emitted in the one direction (blue). If the spin of the quantum dot’s electron points down, the photon will be emitted in the opposite direction (red). (Image: Sahand Mahmoodian and Søren Stobbe, NBI)

In a long, laborious process, the research group further developed and tested the photonic chip until it achieved extreme efficiency and Peter Lodahl explains that it was particularly surprising that they could get the photon emission to occur in a way that was not previously thought possible.

Normally, the photons are transmitted in both directions in the photonic waveguide, but in their custom-made photonic chip they could break this symmetry and get the quantum dot to differentiate between emitting a photon right or left, that means emit directional photons. This means full control over the photons and the researchers are beginning to explore how to construct complete quantum network systems based on the new discovery.

“The photons can be sent over long distances via optical fibres, where they whiz through the fibres with very little loss. You could potentially build a network where the photons connect small quantum systems, which are then linked together into a quantum network – a quantum internet,” explains Peter Lodahl.

He adds that while the first basic functionalities are already a reality, the great challenge is now to expand them to large, complex quantum networks.

Source: University of Copenhagen – Niels Bohr Institute

Stanford team demonstrates a graphene-based thermal-to-electricity conversion technology



The Stanford team demonstrates a graphene-based thermal-to-electricity conversion technology

Researchers at Stanford University have recently demonstrated a graphene-based high efficiency thermal-to-electricity conversion technology, called thermionic energy convertor. 

By using graphene as the anode, the efficiency of the device is increased by a factor of 6.7 compared with a traditional tungsten anode. 

This technology can work in a tandem cycle with existing thermal-based power plants and significantly improve their overall efficiencies.


Stanford team creates graphene-based TEC image

 

Hongyuan Yuan and Roger T. Howe, among the leading researchers in the Stanford team, explain that one of the major challenges for wide adoption of TECs is high anode work function, which directly reduces the output voltage as well as the net efficiency. 

The theoretical maximum efficiency for a TEC with a 2 eV work function anode is 3% at a cathode temperature of 1500 K, compared to an astonishing 10-fold increment to 32% with a 1 eV work function anode.

Before the discovery of graphene, the world-record low work function for a conductor was around 1.1 eV to 1.2 eV, which is achieved by lowering the vacuum level through the deposition of a monolayer of CsO on the surface. Superior to any 3D traditional metal, the work function of graphene can be reduced by not only lowering its vacuum level, but also raising its Fermi level by electrostatic gating through a back gate at the same time. 

In this approach, researchers discovered that the work function of graphene reached a new world-low record of 1.0 eV in 2015.
The second major challenge to the success of TEC is high space charge barrier between TEC’s cathode and anode, which directly reduces the output current and thus the net efficiency. 

In order to reduce the space charge barrier, TEC requires a very small vacuum gap to separate the cathode and anode, usually around 10 mm. If the gap is much larger than 10 mm, all the benefit that an ultra-low work function anode could bring would be diminished. In this recent work, the team successfully addressed the above mentioned two challenges, and demonstrated that the previously discovered ultra-low work function graphene can indeed be applied to TEC with a significant amount of efficiency enhancement. 

Compared to a traditionally used tungsten anode, the net efficiency is increased by a factor of 6.7.
The current demonstration of the TEC device is done in an ultra-high vacuum chamber, with many pumps constantly pumping down the pressure. In reality, it will be vital to fabricate such a TEC device and seal it in a vacuum ‘chip’ using nano/micro fabrication techniques. 

Only by making the device small and reliably stable would it be economically feasible in the sustainable energy industry.
The team envisions such a TEC device in the future, which is sealed in a small and thin cell (TEC cell). 

To generate electricity, all you need to do is to attach one side of the cell to a heat source. You may attach a couple of the TEC cells to the water heater at your home to charge your phone. Or attach many TEC cells to a fossil-fuel power station to improve its overall efficiency.

Thermionic energy convertors (TECs) were primarily used as the energy source for satellites. However, TEC research and its application stagnated until recently. Over the past ten years, with the development in modern wafer-scale fabrication techniques, device physics and material science, as well as an increasing attention to clean and renewable energy globally, TEC has again received a considerable amount of interest both in the academia and industry. 

Despite the limited application at the moment, with improvement in efficiency and device stability, TECs are expected to see an enormous market both in the centralized power plants, i.e. in a tandem cycle, as well as in the distributed systems, e.g. automobiles with internal combustion engines and domestic houses with water heaters.

Source: sciencedirect

U of Michigan: ‘5-D protein fingerprinting’ could give insights into Alzheimer’s, Parkinson’s


5d-fingerprint-alz-587e89833f3c8This illustration depicts the device used to measure individual protein. The inset shows proteins (in red) flowing through a nanopore. Credit: University of Michigan

In research that could one day lead to advances against neurodegenerative diseases like Alzheimer’s and Parkinson’s, University of Michigan engineering researchers have demonstrated a technique for precisely measuring the properties of individual protein molecules floating in a liquid.

 

Proteins are essential to the function of every cell. Measuring their properties in blood and other body fluids could unlock valuable information, as the molecules are a vital building block in the body. The body manufactures them in a variety of complex shapes that can transmit messages between cells, carry oxygen and perform other important functions.

Sometimes, however, proteins don’t form properly. Scientists believe that some types of these misshapen proteins, called amyloids, can clump together into masses in the brain. The sticky tangles block normal cell function, leading to brain cell degeneration and disease.

But the processes of how amyloids form and clump together are not well understood. This is due in part to the fact that there’s currently not a good way to study them. Researchers say current methods are expensive, time-consuming and difficult to interpret, and can only provide a broad picture of the overall level of amyloids in a patient’s system.

The University of Michigan and University of Fribourg researchers who developed the new technique believe that it could help solve the problem by measuring an individual molecule’s shape, volume, electrical charge, rotation speed and propensity for binding to other molecules.

They call this information a “5-D fingerprint” and believe that it could uncover new information that may one day help doctors track the status of patients with and possibly even develop new treatments. Their work is detailed in a paper published in Nature Nanotechnology.

“Imagine the challenge of identifying a specific person based only on their height and weight,” said David Sept, a U-M biomedical engineering professor who worked on the project. “That’s essentially the challenge we face with current techniques. Imagine how much easier it would be with additional descriptors like gender, hair color and clothing. That’s the kind of new information 5-D fingerprinting provides, making it much easier to identify specific proteins.”

'5-D protein fingerprinting' could give insights into Alzheimer's, Parkinson's
This illustration depicts a side view of proteins (blue) flowing through two electrically charged nanopores. Credit: University of Michigan

Michael Mayer, the lead author on the study and a former U-M researcher who’s now a biophysics professor at Switzerland’s Adolphe Merkle Institute, says identifying individual proteins could help doctors keep better tabs on the status of a patient’s disease, and it could also help researchers gain a better understanding of exactly how are involved with neurodegenerative disease.

To take the detailed measurements, the research team uses a nanopore 10-30 nanometers wide—so small that only one protein molecule can fit through at a time. The researchers filled the nanopore with a salt solution and passed an electric current through the solution.

As a protein molecule tumbles through the nanopore, its movement causes tiny, measurable fluctuations in the . By carefully measuring this current, the researchers can determine the protein’s unique five-dimensional signature and identify it nearly instantaneously.

“Amyloid molecules not only vary widely in size, but they tend to clump together into masses that are even more difficult to study,” Mayer said. “Because it can analyze each particle one by one, this new method gives us a much better window to how amyloids behave inside the body.”

Ultimately, the team aims to develop a device that doctors and researchers could use to quickly measure proteins in a sample of blood or other body fluid. This goal is likely several years off; in the meantime, they are working to improve the technique’s accuracy, honing it in order to get a better approximation of each ‘s shape. They believe that in the future, the technology could also be useful for measuring proteins associated with heart disease and in a variety of other applications as well.

“I think the possibilities are pretty vast,” Sept said. “Antibodies, larger hormones, perhaps pathogens could all be detected. Synthetic nanoparticles could also be easily characterized to see how uniform they are.”

The study is titled “Real-time shape approximation and fingerprinting of single proteins using a nanopore.”

Explore further: Imaging technique measures toxicity of Alzheimer’s and Parkinson’s proteins

More information: Erik C. Yusko et al. Real-time shape approximation and fingerprinting of single proteins using a nanopore, Nature Nanotechnology (2016). DOI: 10.1038/nnano.2016.267

U of M Amherst: Developing ‘green’ electronics: Microbes yield better electronic materials


green-elec-microbiologiAn artist’s rendition of Geobacter expressing electrically conductive nanowires. Microbiologists at UMass Amherst have discovered a new type of natural wire produced by bacteria that could greatly accelerate the development of sustainable …more

Microbiologists at the University of Massachusetts Amherst report that they have discovered a new type of natural wire produced by bacteria that could greatly accelerate the researchers’ goal of developing sustainable “green” conducting materials for the electronics industry. The study by Derek Lovley and colleagues appears this week in mBio, the American Society of Microbiology’s premier journal.

The researchers studied microbial nanowires, protein filaments that bacteria use naturally to make electrical connections with other microbes or minerals.

As Lovley explains, “Microbial nanowires are a revolutionary electronic material with substantial advantages over man-made materials. Chemically synthesizing nanowires in the lab requires toxic chemicals, high temperatures and/or expensive metals. The energy requirements are enormous. By contrast, natural microbial nanowires can be mass-produced at room temperature from inexpensive renewable feedstocks in bioreactors with much lower energy inputs. And the final product is free of toxic components.”

“Microbial nanowires therefore offer an unprecedented potential for developing novel materials, electronic devices and sensors for diverse applications with a new environmentally friendly technology,” he adds. “This is an important advance in microbial nanowire technology. The approach we outline in this paper demonstrates a rapid method for prospecting in nature to find better electronic materials.”

Until now Lovely’s lab has been working with the nanowires of just one bacterium, Geobacter sulfurreducens. “Our early studies focused on the one Geobacter because we were just trying to understand why a microbe would make tiny wires,” Lovley says. “Now we are most interested in the nanowires as an electronic material and would like to better understand the full scope of what nature may have to offer for these practical applications.”

When his lab began looking at the protein filaments of other Geobacter species, they were surprised to find a wide range in conductivities. For example, one species recovered from uranium-contaminated soil produced poorly conductive filaments. However, another species, Geobacter metallireducens – coincidentally the first Geobacter ever isolated – produced nanowires 5,000 times more conductive than the G. sulfurreducens wires. Lovley recalls, ” I isolated metallireducens from mud in the Potomac River 30 years ago, and every couple of years it gives us a new surprise.”

In their new study supported by the U.S. Office of Naval Research, they did not study the G. metallireducens strain directly. Instead, they took the gene for the protein that assembles into microbial nanowires from it and inserted this into G. sulfurreducens. The result is a genetically modified G. sulfurreducens that expresses the G. metallireducens protein, making nanowires much more conductive than G. sulfurreducens would naturally produce.

Further, Lovley says, “We have found that G. sulfurreducens will express filament genes from many different types of bacteria. This makes it simple to produce a diversity of filaments in the same microorganism and to study their properties under similar conditions.”

“With this approach, we are prospecting through the to see what is out there in terms of useful conductive materials,” he adds. “There is a vast reservoir of filament genes in the microbial world and now we can study the filaments produced from those genes even if the gene comes from a microbe that has never been cultured.”

The researchers attribute G. metallireducens nanowires’ extraordinarily high conductivity to its greater abundance of aromatic amino acids. Closely packed aromatic rings appear to be a key component of microbial nanowire conductivity, and more aromatic rings probably means better connections for electron transfer along the .

The high conductivity of the G. metallireducens nanowires suggests that they may be an attractive material for the construction of conductive materials, electronic devices and sensors for medical or environmental applications. The authors say discovering more about the mechanisms of nanowire conductivity “provides important insight into how we might make even better wires with genes that we design ourselves.”

Explore further: ‘Green’ electronic materials produced with synthetic biology

More information: Expressing the Geobacter metallireducens PilA in Geobacter sulfurreducens Yields Pili with Exceptional Conductivity, DOI: 10.1128/mBio.02203-16 , http://mbio.asm.org/content/8/1/e02203-16.abstract

 

U of Cambridge: Awakening Graphene’s ‘Sleeping-Giant’ Superconductivity


graphene-super-conductivity-1-graphene-1                             Credit: AlexanderAlUS/Wikipedia/CC BY-SA 3.0

Researchers have found a way to trigger the innate, but previously hidden, ability of graphene to act as a superconductor – meaning that it can be made to carry an electrical current with zero resistance.

The finding, reported in Nature Communications, further enhances the potential of , which is already widely seen as a material that could revolutionise industries such as healthcare and electronics. Graphene is a two-dimensional sheet of carbon atoms and combines several remarkable properties; for example, it is very strong, but also light and flexible, and highly conductive.

Since its discovery in 2004, scientists have speculated that graphene may also have the capacity to be a superconductor. Until now, in graphene has only been achieved by doping it with, or by placing it on, a superconducting material – a process which can compromise some of its other properties.

But in the new study, researchers at the University of Cambridge managed to activate the dormant potential for graphene to superconduct in its own right. This was achieved by coupling it with a material called praseodymium cerium copper oxide (PCCO).

Graphene 2D 070516 integratedtrSuperconductors are already used in numerous applications. Because they generate large magnetic fields they are an essential component in MRI scanners and levitating trains. They could also be used to make energy-efficient power lines and devices capable of storing energy for millions of years.

Superconducting graphene opens up yet more possibilities. The researchers suggest, for example, that graphene could now be used to create new types of superconducting quantum devices for high-speed computing. Intriguingly, it might also be used to prove the existence of a mysterious form of superconductivity known as “p-wave” superconductivity, which academics have been struggling to verify for more than 20 years.

The research was led by Dr Angelo Di Bernardo and Dr Jason Robinson, Fellows at St John’s College, University of Cambridge, alongside collaborators Professor Andrea Ferrari, from the Cambridge Graphene Centre; Professor Oded Millo, from the Hebrew University of Jerusalem, and Professor Jacob Linder, at the Norwegian University of Science and Technology in Trondheim.

“It has long been postulated that, under the right conditions, graphene should undergo a superconducting transition, but can’t,” Robinson said. “The idea of this experiment was, if we couple graphene to a superconductor, can we switch that intrinsic superconductivity on? The question then becomes how do you know that the superconductivity you are seeing is coming from within the graphene itself, and not the underlying superconductor?”Graphene020216 NewsImage_34318

Similar approaches have been taken in previous studies using metallic-based , but with limited success. “Placing graphene on a metal can dramatically alter the properties so it is technically no longer behaving as we would expect,” Di Bernardo said. “What you see is not graphene’s intrinsic superconductivity, but simply that of the underlying superconductor being passed on.”

PCCO is an oxide from a wider class of superconducting materials called “cuprates”. It also has well-understood electronic properties, and using a technique called scanning and tunnelling microscopy, the researchers were able to distinguish the superconductivity in PCCO from the superconductivity observed in graphene.

Superconductivity is characterised by the way the electrons interact: within a superconductor electrons form pairs, and the spin alignment between the electrons of a pair may be different depending on the type – or “symmetry” – of superconductivity involved. In PCCO, for example, the pairs’ spin state is misaligned (antiparallel), in what is known as a “d-wave state”.

By contrast, when graphene was coupled to superconducting PCCO in the Cambridge-led experiment, the results suggested that the electron pairs within graphene were in a p-wave state. “What we saw in the graphene was, in other words, a very different type of superconductivity than in PCCO,” Robinson said. “This was a really important step because it meant that we knew the superconductivity was not coming from outside it and that the PCCO was therefore only required to unleash the intrinsic superconductivity of graphene.”

It remains unclear what type of superconductivity the team activated, but their results strongly indicate that it is the elusive “p-wave” form. If so, the study could transform the ongoing debate about whether this mysterious type of superconductivity exists, and – if so – what exactly it is.

In 1994, researchers in Japan fabricated a triplet superconductor that may have a p-wave symmetry using a material called strontium ruthenate (SRO). The p-wave symmetry of SRO has never been fully verified, partly hindered by the fact that SRO is a bulky crystal, which makes it challenging to fabricate into the type of devices necessary to test theoretical predictions.

“If p-wave superconductivity is indeed being created in graphene, graphene could be used as a scaffold for the creation and exploration of a whole new spectrum of superconducting devices for fundamental and applied research areas,” Robinson said. “Such experiments would necessarily lead to new science through a better understanding of p-wave superconductivity, and how it behaves in different devices and settings.”

The study also has further implications. For example, it suggests that graphene could be used to make a transistor-like device in a superconducting circuit, and that its superconductivity could be incorporated into molecular electronics. “In principle, given the variety of chemical molecules that can bind to graphene’s surface, this research can result in the development of molecular electronics devices with novel functionalities based on superconducting graphene,” Di Bernardo added.

Explore further: Graphene becomes superconductive—Electrons with ‘no mass’ flow with ‘no resistance’

More information: P-wave triggered superconductivity in single layer graphene on an electron-doped oxide superconductor, Nature Communications, DOI: 10.1038/NCOMMS14024