Atomic-scale capillaries block smallest ions thanks to Graphene – Structures are ideal in Desalination and Filtration Technologies


graphene atomicscalec de sal                                       Credit: University of Manchester

 

** See More About Graphene (YouTube Video) and Desalination at the end of this article **

Researchers at The University of Manchester’s National Graphene Institute in the UK have succeeded in making artificial channels just one atom in size for the first time. The new capillaries, which are very much like natural protein channels such as aquaporins, are small enough to block the flow of smallest ions like Na+ and Cl- but allow water to flow through freely. As well as improving our fundamental understanding of molecular transport at the atomic scale, and especially in biological systems, the structures could be ideal in desalination and filtration technologies.

“Obviously, it is impossible to make capillaries smaller than one atom in size,” explains team leader Sir Andre Geim. “Our feat seemed nigh on impossible, even in hindsight, and it was difficult to imagine such tiny capillaries just a couple of years ago.”

Naturally occurring protein channels, such as aquaporins, allow water to quickly permeate through them but block hydrated ions larger than around 7 A in size thanks to mechanisms like steric (size) exclusion and electrostatic repulsion. Researchers have been trying to make artificial capillaries that work just like their natural counterparts, but despite much progress in creating nanoscale pores and nanotubes, all such structures to date have still been much bigger than biological channels.

Geim and colleagues have now fabricated channels that are around just 3.4 A in height. This is about half the size of the smallest hydrated ions, such as K+ and Cl-, which have a diameter of 6.6 A. These channels behave just like protein channels in that they are small enough to block these ions but are sufficiently big to allow water molecules (with a diameter of around 2.8 A) to freely flow through.

The structures could, importantly, help in the development of cost-effective, high-flux filters for water desalination and related technologies – a holy grail for researchers in the field.

Credit: University of Manchester

Atomic-scale Lego

Publishing their findings in Science the researchers made their structures using a van der Waals assembly technique, also known as “atomic-scale Lego”, which was invented thanks to research on graphene. “We cleave atomically flat nanocrystals just 50 and 200 nanometre in thickness from bulk graphite and then place strips of monolayer graphene onto the surface of these nanocrystals,” explains Dr. Radha Boya, a co-author of the research paper. “These strips serve as spacers between the two crystals when a similar atomically-flat crystal is subsequently placed on top. The resulting trilayer assembly can be viewed as a pair of edge dislocations connected with a flat void in between. This space can accommodate only one atomic layer of water.”

Using the  monolayers as spacers is a first and this is what makes the new channels different from any previous structures, she says.

The Manchester scientists designed their 2-D capillaries to be 130 nm wide and several microns in length. They assembled them atop a silicon nitride membrane that separated two isolated containers to ensure that the channels were the only pathway through which water and ions could flow.

Until now, researchers had only been able to measure water flowing though capillaries that had much thicker spacers (around 6.7 A high). And while some of their  indicated that smaller 2-D cavities should collapse because of van der Waals attraction between the opposite walls, other calculations pointed to the fact that  inside the slits could actually act as a support and prevent even one-atom-high slits (just 3.4 A tall) from falling down. This is indeed what the Manchester team has now found in its experiments.

Measuring water and ion flow

“We measured water permeation through our channels using a technique known as gravimetry,” says Radha. “Here, we allow water in a small sealed container to evaporate exclusively through the capillaries and we then accurately measure (to microgram precision) how much weight the container loses over a period of several hours.”

To do this, the researchers say they built a large number of channels (over a hundred) in parallel to increase the sensitivity of their measurements. They also used thicker top crystals to prevent sagging, and clipped the top opening of the capillaries (using plasma etching) to remove any potential blockages by thin edges present here.

To measure ion flow, they forced ions to move through the capillaries by applying an electric field and then measured the resulting currents. “If our capillaries were two atoms high, we found that small ions can move freely though them, just like what happens in bulk water,” says Radha. “In contrast, no ions could pass through our ultimately-small one-atom-high channels.

“The exception was protons, which are known to move through water as true subatomic particles, rather than ions dressed up in relatively large hydration shells several angstroms in diameter. Our channels thus block all hydrated ions but allow protons to pass.”

Since these  behave in the same way as protein channels, they will be important for better understanding how water and ions behave on the molecular scale – as in angstrom-scale biological filters. “Our work (both present and previous) shows that atomically-confined water has very different properties from those of bulk ,” explains Geim. “For example, it becomes strongly layered, has a different structure, and exhibits radically dissimilar dielectric properties.”

 Explore further: Devices made from 2-D materials separate salts in seawater

More information: Dorri Halbertal et al. Imaging resonant dissipation from individual atomic defects in graphene, Science (2017). DOI: 10.1126/science.aan0877 , https://arxiv.org/abs/1811.09227

Want to Read More About Cutting Edge Desalination, Energy Storage and Carbon Nanotubes?

opt-cnts-for-water-wang-mutha-nanotubes_0MIT: Optimizing carbon nanotube electrodes for energy storage and water desalination applications

 

 

 

Graphene for Water Desalination

 

Water, one of the world’s most abundant and highly demanded resources for sustaining life, agriculture, and industry, is being contaminated globally or is unsafe for drinking, creating a need for new and better desalination methods. Current desalination methods have high financial, energy, construction, and operating costs, resulting in them contributing to less than 1% of the world’s reserve water supplies. Advances in nanoscale science and engineering suggest that more cost effective and environmentally friendly desalination process using graphene is possible …

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MIT: Physicists record ‘lifetime’ of graphene qubits – Foundation for Advancing Quantum Computing


 

Researchers from MIT and elsewhere have recorded, for the first time, the “temporal coherence” of a graphene qubit

The demonstration, which used a new kind of graphene-based qubit, meaning how long it can maintain a special state that allows it to represent two logical states simultaneously, represents a critical step forward for practical quantum computing, the researchers say.

Superconducting quantum bits (simply, qubits) are artificial atoms that use various methods to produce bits of quantum information, the fundamental component of quantum computers. Similar to traditional binary circuits in computers, qubits can maintain one of two states corresponding to the classic binary bits, a 0 or 1.

But these qubits can also be a superposition of both states simultaneously, which could allow quantum computers to solve complex problems that are practically impossible for traditional computers.

The amount of time that these qubits stay in this superposition state is referred to as their “coherence time.” The longer the coherence time, the greater the ability for the qubit to compute complex problems.

Recently, researchers have been incorporating graphene-based materials into superconducting quantum computing devices, which promise faster, more efficient computing, among other perks.

Until now, however, there’s been no recorded coherence for these advanced qubits, so there’s no knowing if they’re feasible for practical quantum computing. In a paper published today in Nature Nanotechnology, the researchers demonstrate, for the first time, a coherent qubit made from graphene and exotic materials.

These materials enable the qubit to change states through voltage, much like transistors in today’s traditional computer chips — and unlike most other types of superconducting qubits. Moreover, the researchers put a number to that coherence, clocking it at 55 nanoseconds, before the qubit returns to its ground state.

The work combined expertise from co-authors William D. Oliver, a physics professor of the practice and Lincoln Laboratory Fellow whose work focuses on quantum computing systems, and Pablo Jarillo-Herrero, the Cecil and Ida Green Professor of Physics at MIT who researches innovations in graphene.

“Our motivation is to use the unique properties of graphene to improve the performance of superconducting qubits,” says first author Joel I-Jan Wang, a postdoc in Oliver’s group in the Research Laboratory of Electronics (RLE) at MIT.

“In this work, we show for the first time that a superconducting qubit made from graphene is temporally quantum coherent, a key requisite for building more sophisticated quantum circuits. Ours is the first device to show a measurable coherence time — a primary metric of a qubit — that’s long enough for humans to control.”

There are 14 other co-authors, including Daniel Rodan-Legrain, a graduate student in Jarillo-Herrero’s group who contributed equally to the work with Wang; MIT researchers from RLE, the Department of Physics, the Department of Electrical Engineering and Computer Science, and Lincoln Laboratory; and researchers from the Laboratory of Irradiated Solids at the École Polytechnique and the Advanced Materials Laboratory of the National Institute for Materials Science.

A pristine graphene sandwich

Superconducting qubits rely on a structure known as a “Josephson junction,” where an insulator (usually an oxide) is sandwiched between two superconducting materials (usually aluminum).

In traditional tunable qubit designs, a current loop creates a small magnetic field that causes electrons to hop back and forth between the superconducting materials, causing the qubit to switch states.

But this flowing current consumes a lot of energy and causes other issues. Recently, a few research groups have replaced the insulator with graphene, an atom-thick layer of carbon that’s inexpensive to mass produce and has unique properties that might enable faster, more efficient computation.

To fabricate their qubit, the researchers turned to a class of materials, called van der Waals materials — atomic-thin materials that can be stacked like Legos on top of one another, with little to no resistance or damage.

These materials can be stacked in specific ways to create various electronic systems. Despite their near-flawless surface quality, only a few research groups have ever applied van der Waals materials to quantum circuits, and none have previously been shown to exhibit temporal coherence.

For their Josephson junction, the researchers sandwiched a sheet of graphene in between the two layers of a van der Waals insulator called hexagonal boron nitride (hBN). Importantly, graphene takes on the superconductivity of the superconducting materials it touches.

The selected van der Waals materials can be made to usher electrons around using voltage, instead of the traditional current-based magnetic field. Therefore, so can the graphene — and so can the entire qubit.

 

When voltage gets applied to the qubit, electrons bounce back and forth between two superconducting leads connected by graphene, changing the qubit from ground (0) to excited or superposition state (1). The bottom hBN layer serves as a substrate to host the graphene.

The top hBN layer encapsulates the graphene, protecting it from any contamination. Because the materials are so pristine, the traveling electrons never interact with defects. This represents the ideal “ballistic transport” for qubits, where a majority of electrons move from one superconducting lead to another without scattering with impurities, making a quick, precise change of states.

How voltage helps

The work can help tackle the qubit “scaling problem,” Wang says. Currently, only about 1,000 qubits can fit on a single chip. Having qubits controlled by voltage will be especially important as millions of qubits start being crammed on a single chip.

“Without voltage control, you’ll also need thousands or millions of current loops too, and that takes up a lot of space and leads to energy dissipation,” he says.

Additionally, voltage control means greater efficiency and a more localized, precise targeting of individual qubits on a chip, without “cross talk.” That happens when a little bit of the magnetic field created by the current interferes with a qubit it’s not targeting, causing computation problems.

For now, the researchers’ qubit has a brief lifetime. For reference, conventional superconducting qubits that hold promise for practical application have documented coherence times of a few tens of microseconds, a few hundred times greater than the researchers’ qubit.

But the researchers are already addressing several issues that cause this short lifetime, most of which require structural modifications. They’re also using their new coherence-probing method to further investigate how electrons move ballistically around the qubits, with aims of extending the coherence of qubits in general.

Coherent control of a hybrid superconducting circuit made with graphene-based van der Waals heterostructures
Joel I-Jan Wang, Daniel Rodan-Legrain, Landry Bretheau, Daniel L. Campbell, Bharath Kannan, David Kim, Morten Kjaergaard, Philip Krantz, Gabriel O. Samach, Fei Yan, Jonilyn L. Yoder, Kenji Watanabe, Takashi Taniguchi, Terry P. Orlando, Simon Gustavsson, Pablo Jarillo-Herrero & William D. Oliver
Nature Nanotechnology (2018)
DOI: 10.1038_s41565-018-0329-2

Contact information:

William D. Oliver
MIT Physics Professor of the Practice
oliver@ll.mit.edu URL: http://www.rle.mit.edu/

Pablo Jarillo-Herrero
MIT Physics Professor
pjarillo@mit.edu URL: http://jarilloherrero.mit.edu/

Massachusetts Institute of Technology (MIT)

 

Aerospace Potential for Graphene – Provides Superior Mechanical and Thermal Properties – Lower Fuel and Operating Costs


Aernnova, Grupo Antolin-Ingenieria and Airbus – as partners in the Graphene Flagship, the European Union’s largest-ever research initiative with funding of EUR 1 billion – have produced a leading edge for the Airbus A350 horizontal tail plane using graphene-enhanced composites.

“We worked together with Grupo Antolin-Ingenieria and Airbus as part of the Graphene Flagship’s production work package and our collaboration greatly benefitted from the discussions during meetings,” said Ana Reguero of Aernnova.

“Airbus brought us – as the manufacturer of the current leading edge – together with Grupo Antolin-Ingenieria on the project.”

Aernnova, Grupo Antolin-Ingenieria and Airbus produced a leading edge for the Airbus A350 horizontal tail plane using graphene-enhanced composites. © Graphene Flagship

As the first part of the tail plane to contact air, the leading edge is subjected to extreme temperatures caused by compressive heating of the air ahead of the wing. Thus, it must possess excellent mechanical and thermal properties.

“Aernnova supplied the resin to Grupo Antolin-Ingenieria who added graphene directly to the resin and applied milling forces,” said Reguero.

This creates small graphene particles – an important step to get good graphene infiltration within the resin, avoiding unwanted impurities, such as solvents, which can alter the viscosity of the resin.  It is important to maintain the correct viscosity of the resin to ensure the optimal outcome during the resin transfer moulding of the leading edge.”

At a component level the team found that the resin with the added graphene showed increased mechanical and thermal properties, including a decreased fracture speed.

By increasing the resin properties with graphene, it will be possible to make the tail edge thinner, decreasing its weight while maintaining its safety. This will provide a significant saving in fuel and therefore costs and emissions over the aircraft lifetime.

At a component level the team found that the resin with the added graphene showed increased mechanical and thermal properties. © Graphene Flagship

“Our small-scale tests showed an increase in properties. We will next test a one third scale model,” said Reguero.

“This is a great example of the collaborations fostered by the Graphene Flagship,” said Professor Andrea C. Ferrari, its science and technology officer. “Three of our industrial partners came together to address a key problem and found that graphene offers a solution beyond the state of the art.

The development and system integration of graphene-based technologies follows the plans of our innovation and technology, where composite technologies play a prominent role.”

Scientists at the University of Manchester develop revolutionary method for graphene printed electronics – Impact for IoT


graphene post 1This visualisation shows layers of graphene used for membranes. Credit: University of Manchester

 

A team of researchers based at The University of Manchester have found a low cost method for producing graphene printed electronics, which significantly speeds up and reduces the cost of conductive graphene inks.

Printed electronics offer a breakthrough in the penetration of information technology into everyday life. The possibility of printing  will further promote the spread of Internet of Things (IoT) .

The development of printed conductive inks for electronic applications has grown rapidly, widening applications in transistors, sensors, antennas RFID tags and wearable electronics.

Current conductive inks traditionally use metal nanoparticles for their high electrical conductivity. However, these  can be expensive or easily oxidised, making them far from ideal for low cost IoT applications.

The team have found that using a material called dihydro-levo-gucosenone known as Cyrene is not only non-toxic but is environmentally- friendly and sustainable but can also provide higher concentrations and conductivity of  ink.

Professor Zhiurn Hu said: “This work demonstrates that printed graphene technology can be low cost, sustainable, and environmentally friendly for ubiquitous wireless connectivity in IoT era as well as provide RF energy harvesting for low power electronics”.

Professor Sir Kostya Novoselov said: “Graphene is swiftly moving from research to application domain. Development of production methods relevant to the end-user in terms of their flexibility, cost and compatibility with existing technologies are extremely important. This work will ensure that implementation of graphene into day-to-day products and technologies will be even faster”.

Kewen Pan, the lead author on the paper said: “This perhaps is a significant step towards commercialisation of printed graphene technology. I believe it would be an evolution in printed electronics industry because the material is such low cost, stable and environmental friendly”.

The National Physical Laboratory (NPL), who were involved in measurements for this work, have partnered with the National Graphene Institute at The University of Manchester to provide a materials characterisation service to provide the missing link for the industrialisation of graphene and 2-D materials. They have also published a joint NPL and NGI a good practice guide which aims to tackle the ambiguity surrounding how to measure graphene’s characteristics.

Professor Ling Hao said: “Materials characterisation is crucial to be able to ensure performance reproducibility and scale up for commercial applications of graphene and 2-D materials. The results of this collaboration between the University and NPL is mutually beneficial, as well as providing measurement training for Ph.D. students in a metrology institute environment.”

Graphene has the potential to create the next generation of electronics currently limited to science fiction: faster transistors, semiconductors, bendable phones and flexible wearable electronics.

 Explore further: Fully integrated circuits printed directly onto fabric

 

Holey graphene as ‘Holy Grail’ alternative to silicon chips – turning graphene into a semiconductor


3D Graphene

Graphene, in its regular form, does not offer an alternative to silicon chips for applications in nanoelectronics. It is known for its energy band structure, which leaves no energy gap and no magnetic effects.

Graphene antidot lattices, however, are a new type of graphene device that contain a periodic array of holes—missing several atoms in the otherwise regular single layer of carbon atoms. This causes an energy band gap to open up around the baseline energy level of the material, effectively turning graphene into a semiconductor.

 

In a new study published in EPJ B, Iranian physicists investigate the effect of antidot size on the electronic structure and magnetic properties of triangular antidots in graphene. Zahra Talebi Esfahani from Payame Noor University in Tehran, Iran, and colleagues have confirmed the existence of a band gap opening in such antidot graphene lattices, which depends on the electron’s spin degree of freedom, and which could be exploited for applications like spin transistors. The authors perform simulations using holes that are shaped like right and equilateral triangles, to explore the effects of both the armchair-shaped and zigzag-shaped edges of graphene holes on the material’s characteristics.

In this study, the values of the  and the total magnetisation, the authors find, depend on the size, shape and spacing of the antidots. These may actually increase with the number of zigzag edges around the holes. The induced  are mainly localised on the edge atoms, with a maximum value at the centre of each side of the equilateral triangle. By contrast, armchair edges display no local magnetic moment.

Thanks to the energy band gap created, such periodic arrays of triangular antidot lattices can be used as magnetic semiconductors. And because the  band gap depends on the electron spins in the material, magnetic antidot lattices are ideal candidates for spintronic applications.

 Explore further: Artificial magnetic field produces exotic behavior in graphene sheets

More information: Zahra Talebi Esfahani et al, A DFT study on the electronic and magnetic properties of triangular graphene antidot lattices, The European Physical Journal B (2018). DOI: 10.1140/epjb/e2018-90517-6

 

New Hybrid solar cells harness energy from … raindrops?


Renewable energy is the cleanest and inexhaustible source of energy. They are a great alternative to fossil fuels.

Renewable energy doesn’t emit any greenhouse gases in the environment. They are environment-friendly and help us tackle the most important concern of the 21st Century – Climate Change.

Solar is one of the most important forms of renewable energy. Sun is an inexhaustible source of energy and solar cells help capture that clean energy for both commercial and domestic purposes. Despite all these advantages, Solar cells are not efficient when it comes to producing energy during rainy seasons. Since the input energy gets reduced, solar cells become practically useless when rain clouds are overhead.

But what if we could overcome this problem?  What if we could actually generate energy from raindrops?

Scientists from the University of Soochow, China have overcome the design flaw of solar cells by allowing them to generate energy both in the sunny and rainy season.

This technology holds the potential of revolutionizing renewable energy completely.

The key part of this new Hybrid solar technology is the triboelectric nanogenerator or TENG. A device capable of producing an electric charge from the friction of two materials rubbing together.

How Hybrid solar cells work?

These new hybrid solar cells works using a material called Graphene. It has the ability to produce energy from raindrops.

Like any other solar panel, these hybrid solar cells also generate electricity during a normal sunny day using the current technology, but when cloud gathers and raindrop falls, this solar panels system switch to its graphene system.

Graphene, in its liquid form, can produce electricity due to the presence of delocalized electrons that help us create a pseudocapacitor framework. This pseudo framework helps us generate electricity.

When raindrops fall on hybrid solar panels, they get separated as positive ions and negative ions.

These positive ions are mainly salt-related ions, like sodium and calcium which accumulates on the surface of graphene. These positive ions interact with the loosely associated negative ions in graphene and create a system that acts like a pseudocapacitor.

The difference in potential between these ions produces current and voltage.

Although, it is important to mention that this is not a first attempt to invent all-weathered Solar panels. Earlier, researchers created a solar panel with triboelectric nanogenerator on top, an insulating layer in the middle and solar panel at the bottom. But this system possessed too much electrical resistance and sunlight was not able to reach the solar cells due to the opaque nature of insulators.

The newly designed hybrid solar panel is an efficient device, where the triboelectric nanogenerator and the solar panel share a common and transparent electrode. There are special grooves incorporated in the material which increases the efficiency of both raindrops and sunlight captured.

According to the researchers, the idea of special grooves was derived from commercial DVD’s. DVD’s come pre-etched with parallel grooves just hundreds of nanometer across. Designing the device with this grooves helps to boost the surface interaction of raindrops and sunlight that would be otherwise lost to reflection.

Benefits of Solar Hybrid Panels  

Until now solar cells have this drawback of producing energy only in the presence of sunlight, making it impossible to harness energy during the rainy season. Countries in the northern hemisphere were not able to switch to solar energy due to the presence of low-intensity sunlight.

With hybrid solar panels, anyone in the world could harness solar power. Researchers expect that in a few years, these panels will be efficient enough to provide electricity for homes and businesses and thus ending our dependency on fossil fuels.

They will also save a lot of money on daily electricity bills. Even though the initial setup costs are higher, countries with good exposure to both sunlight and rain can expect a good ROI.

Hurdles in Solar hybrid panels    

The current designs are not efficient enough to be used commercially. The device was tested in various simulated weather conditions, in sunlight, the device was able to produce around 13% efficiency and simulated raindrops had an efficiency of around 6%.

Currently used commercial solar cells gives an efficiency of around 15%, thus the new design is a viable option for presently used solar panels. However, the efficiency of triboelectric nanogenerators was not reported.

Conclusion

With continuous depletion of non-renewable sources and the disastrous climate change occurring due to fossil fuels, many countries are moving towards eco-friendly alternatives. Solar energy is one of the cleanest energy available. With the advent of new technology like the hybrid solar panels, we can hope to achieve a viable method of electricity generation.

Researchers are continuously trying to improve the efficiency of hybrid solar cells in order to make it commercially available. This will boost our efforts of producing energy in all-weather condition, which is not possible with the currently available technology. With the expansion of solar energy projects worldwide, researchers of hybrid solar cells are expecting to roll out commercial designs in next five years.

Researchers at china are even trying to integrate this new technology into mobile and electronic device such as electronic clothing.     

LLNL Researchers Develop New Class of 3D PRINTED METAMATERIALS that Strengthen “On Demand” – Applications for armor that responds on impact; car seats that reduce whiplash and NextGen Neck braces


Combining 3D printing with a magnetic ink injection, researchers at Lawrence Livermore National Laboratory (LLNL) have created a new class of metamaterial – engineered with behaviors outside their nature.

Like 4D printed objects, LLNL’s 3D printed lattices rely on the fourth element of time to become something “other” than their natural resting state. However, in contrast to its relatives, that often transform in response to temperatures or water, the change in LLNL’s new structures is almost instantaneous – they stiffen when a magnetic field is applied.

This unique class is the next step forward in metamaterials that can be tuned “on-the-fly” to achieve desired properties, and applied to make intuitive objects: e.g. armor that responds on impact; car seats that reduce whiplash; and next generation neck braces.

A 3D printed lattice injected with magnetic fluid. Image via Science Advances, supplementary materials/LLNL

A 3D printed lattice injected with magnetic fluid. Image via Science Advances, supplementary materials/LLNL

Harnessing the power of lattices

In the first stage of this development, the LLNL team performed a digital simulation of their metamaterial lattices. By doing so, the team could determine how the shape would respond to a magnetic field, and therefore optimize its structure for desired mechanical properties.

Mark Messner, former LLNL researcher and co-author of a study presenting the new metamaterial, explains, “The design space of possible lattice structures is huge, so the model and the optimization process helped us choose likely structures with favorable properties before [it was] printed, filled and tested the actual specimens, which is a lengthy process.”

After optimization, experimental lattices were 3D printed using a method of Large Area Projection Microstereolithography (LAPµSL). With microscale precision, LAPµSL enabled the team to create thin walls that could support injected fluid.

Lead author Julie Jackson Mancini explains, “In this paper we really wanted to focus on the new concept of metamaterials with tunable properties, and even though it’s a little more of a manual fabrication process,” i.e. with the injection of material, “it still highlights what can be done, and that’s what I think is really exciting.”

Materials with “on-the-fly” tunability 

The ink inside the LLNL lattice is a magnetorheological fluid, containing minute magnetic particles.

Like a “dancing” iron filing experiment, when a magnetic field is applied to this lattice, the particles realign, making the structure stiff and supportive of added weight.

This newfound strength is demonstrated through a test in which a 10g weight is added to the top of the lattice. As the magnet beneath the lattice is moved away, the structure gradually gives way, and eventually drops the weight.

Demonstration showing a 3D printing magnetic metamaterial lattice, and its response to the removal of a magnetic field. Image via Science Advance, supplementary materials/LLNL

Demonstration showing a 3D printing magnetic metamaterial lattice, and its response to the removal of a magnetic field. Image via Science Advance, supplementary materials/LLNL

“What’s really important,” explains Mancini, “is it’s not just an on and off response, by adjusting the magnetic field strength applied we can get a wide range of mechanical properties,”

“THE IDEA OF ON-THE-FLY, REMOTE TUNABILITY OPENS THE DOOR TO A LOT OF APPLICATIONS.”

Future development

The next steps for the LLNL metamaterial team is to develop a means of integrating the ink-injection stage of lattice fabrication, and to increase the size of objects that can be 3D printed.

Results of the lab’s most recent study, “Field responsive mechanical metamaterials” are published online in Science Advances journal. It’s co-authors are listed as Julie A. JacksonMark C. MessnerNikola A. Dudukovic, William L. SmithLogan BekkerBryan MoranAlexandra M. GolobicAndrew J. PascallEric B. DuossKenneth J. Loh, and Christopher M. Spadaccini.

Nominate 3D Printing Research Team of the Year and more now for the 2019 3D Printing Industry Awards.

Graphene Could Revolutionize the Development of Wearable Electronic Devices


 

graphenehydr

Thanks to the application of the wonder material graphene, the quest for producing durable, affordable, and mass-produced “smart textiles” has been given a new push.

Headed by Professor Monica Craciun from the University of Exeter Engineering department, an international group of researchers has developed a novel method for producing fully electronic fibers that can be integrated into the production of day-to-day clothing.

The development of the current generation of wearable electronics involves fixing devices to fabrics, which could make them extremely rigid and prone to malfunctioning. However, in the latest study, the electronic devices are embedded in the material’s fabric, and this is done by coating electronic fibers with durable and lightweight components that will enable showing images directly on the fabric.

According to the scientists, the discovery could transform the development of wearable electronic devices for applications in many different day-to-day applications, and also medical diagnostics and health monitoring, like blood pressure and heart rates.

The international collaborative study has been reported in the scientific journal Flexible Electronics. Experts from the Centre for Graphene Science at the University of Exeter, CenTexBel in Belgium, and the Universities of Aveiro and Lisbon in Portugal took part in the study.

For truly wearable electronic devices to be achieved, it is vital that the components are able to be incorporated within the material, and not simply added to it.

Monica Craciun, Professor and Study Co-Author, Engineering Department, University of Exeter.

 

 

Graphene is only one-atom thick, which makes it the thinnest substance with the ability to conduct electricity. It is also one of the strongest known materials and quite flexible. In recent years, the race has been on for engineers and scientists to adapt graphene for applications in wearable electronic devices.

The latest study applied existing polypropylene fibers—often employed in an array of commercial applications in the textile sector—to fix the novel, graphene-based electronic fibers to develop light-emitting and touch-sensor devices.

The innovative method means that the fabrics will be capable of integrating truly wearable displays but without the requirement for electrodes—wires of extra materials.

The incorporation of electronic devices on fabrics is something that scientists have tried to produce for a number of years, and is a truly game-changing advancement for modern technology.

Saverio Russo, Professor and Study Co-Author, Physics Department, University of Exeter.

The key to this new technique is that the textile fibres are flexible, comfortable and light, while being durable enough to cope with the demands of modern life.

Dr Ana Neves, Study Co-Author, Engineering Department, University of Exeter.

Earlier in 2015, an international group of researchers, including Dr Ana Neves, Professor Russo, and Professor Craciun from the University of Exeter, had developed a novel method to integrate flexible, transparent graphene electrodes into fibers often associated with the textile sector.

graphene-supercapacitor

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RMIT – Study unlocks full potential of graphene ‘supermaterial’


Drs. Esrafilzadeh and Jalili working on 3D-printed graphene mesh in the lab.
Credit: RMIT University

New research reveals why the “supermaterial” graphene has not transformed electronics as promised, and shows how to double its performance and finally harness its extraordinary potential.

Graphene is the strongest material ever tested. It’s also flexible, transparent and conducts heat and electricity 10 times better than copper.

After graphene research won the Nobel Prize for Physics in 2010 it was hailed as a transformative material for flexible electronics, more powerful computer chips and solar panels, water filters and bio-sensors. But performance has been mixed and industry adoption slow.

Now a study published in Nature Communications identifies silicon contamination as the root cause of disappointing results and details how to produce higher performing, pure graphene.

The RMIT University team led by Dr Dorna Esrafilzadeh and Dr Rouhollah Ali Jalili inspected commercially-available graphene samples, atom by atom, with a state-of-art scanning transition electron microscope.

“We found high levels of silicon contamination in commercially available graphene, with massive impacts on the material’s performance,” Esrafilzadeh said.

Testing showed that silicon present in natural graphite, the raw material used to make graphene, was not being fully removed when processed.

“We believe this contamination is at the heart of many seemingly inconsistent reports on the properties of graphene and perhaps many other atomically thin two-dimensional (2D) materials ,” Esrafilzadeh said.

Graphene has not become the next big thing because of silicon impurities holding it back, RMIT researchers have said.

Graphene was billed as being transformative, but has so far failed to make a significant commercial impact, as have some similar 2D nanomaterials. Now we know why it has not been performing as promised, and what needs to be done to harness its full potential.”

The testing not only identified these impurities but also demonstrated the major influence they have on performance, with contaminated material performing up to 50% worse when tested as electrodes.

“This level of inconsistency may have stymied the emergence of major industry applications for graphene-based systems.

But it’s also preventing the development of regulatory frameworks governing the implementation of such layered nanomaterials, which are destined to become the backbone of next-generation devices,” she said.

The two-dimensional property of graphene sheeting, which is only one atom thick, makes it ideal for electricity storage and new sensor technologies that rely on high surface area.

This study reveals how that 2D property is also graphene’s Achilles’ heel, by making it so vulnerable to surface contamination, and underscores how important high purity graphite is for the production of more pure graphene.

Using pure graphene, researchers demonstrated how the material performed extraordinarily well when used to build a supercapacitator, a kind of super battery.

When tested, the device’s capacity to hold electrical charge was massive. In fact, it was the biggest capacity so far recorded for graphene and within sight of the material’s predicted theoretical capacity.

In collaboration with RMIT’s Centre for Advanced Materials and Industrial Chemistry, the team then used pure graphene to build a versatile humidity sensor with the highest sensitivity and the lowest limit of detection ever reported.

These findings constitute a vital milestone for the complete understanding of atomically thin two-dimensional materials and their successful integration within high performance commercial devices.

“We hope this research will help to unlock the exciting potential of these materials.”

Story Source:

Materials provided by RMIT University. Note: Content may be edited for style and length.


Journal Reference:

  1. Rouhollah Jalili, Dorna Esrafilzadeh, Seyed Hamed Aboutalebi, Ylias M. Sabri, Ahmad E. Kandjani, Suresh K. Bhargava, Enrico Della Gaspera, Thomas R. Gengenbach, Ashley Walker, Yunfeng Chao, Caiyun Wang, Hossein Alimadadi, David R. G. Mitchell, David L. Officer, Douglas R. MacFarlane, Gordon G. Wallace. Silicon as a ubiquitous contaminant in graphene derivatives with significant impact on device performance. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-07396-3

NIST Research Suggests Graphene Can Stretch to be a Tunable Ion Filter – Applications for nanoscale sensors, drug delivery and water purification


 

 

Researchers at the National Institute of Standards and Technology (NIST) have conducted simulations suggesting that graphene, in addition to its many other useful features, can be modified with special pores to act as a tunable filter or strainer for ions (charged atoms) in a liquid.

The concept, which may also work with other membrane materials, could have applications such as nanoscale mechanical sensors, drug delivery, water purification and sieves or pumps for ion mixtures similar to biological ion channels, which are critical to the function of living cells. The research is described in the November 26 issue of Nature Materials.

“Imagine something like a fine-mesh kitchen strainer with sugar flowing through it,” project leader Alex Smolyanitsky said. “You stretch that strainer in such a way that every hole in the mesh becomes 1-2 percent larger. You’d expect that the flow through that mesh will be increased by roughly the same amount. Well, here it actually increases 1,000 percent. I think that’s pretty cool, with tons of applications.”

If it can be achieved experimentally, this graphene sieve would be the first artificial ion channel offering an exponential increase in ion flow when stretched, offering possibilities for fast ion separations or pumps or precise salinity control. Collaborators plan laboratory studies of these systems, Smolyanitsky said.

Graphene is a layer of carbon atoms arranged in hexagons, similar in shape to chicken wire, that conducts electricity. The NIST molecular dynamics simulations focused on a graphene sheet 5.5 by 6.4 nanometers (nm) in size and featuring small holes lined with oxygen atoms. These pores are crown ethers—electrically neutral circular molecules known to trap metal ions. A previous NIST simulation study showed this type of graphene membrane might be used for nanofluidic computing.

In the simulations, the graphene was suspended in water containing potassium chloride, a salt that splits into potassium and chlorine ions. The crown ether pores can trap potassium ions, which have a positive charge. The trapping and release rates can be controlled electrically. An electric field of various strengths was applied to drive the ion current flowing through the membrane.

Researchers then simulated tugging on the membrane with various degrees of force to stretch and dilate the pores, greatly increasing the flow of potassium ions through the membrane. Stretching in all directions had the biggest effect, but even tugging in just one direction had a partial effect.

Researchers found that the unexpectedly large increase in ion flow was due to a subtle interplay of a number of factors, including the thinness of graphene; interactions between ions and the surrounding liquid; and the ion-pore interactions, which weaken when pores are slightly stretched. There is a very sensitive balance between ions and their surroundings, Smolyanitsky said.

The research was funded by the Materials Genome Initiative.


Paper: A. Fang, K. Kroenlein, D. Riccardi and A. Smolyanitsky. Highly mechanosensitive ion channels from graphene-embedded crown ethers. Nature Materials. Published online November 26, 2018. DOI: 10.1038/s41563-018-0220-4