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Showing posts with label Materials. Show all posts
Showing posts with label Materials. Show all posts

Thursday, 13 February 2020

As seen in Movies, Holograms can be used as a communication tool

For the time being the team has only managed to transmit letters and small messages, but the future is promising, as seen in this art. [Image: Nanoscale Horizons]

Those who  have watched the film Black Panther saw people from the Wakanda Kingdom communicating through holograms. And that specific scene of fiction can become a reality sooner than you might imagine, allowing you to exchange different information with people from different locations.

This possibility is being made possible by the creation of "meta-holograms", which are modified versions of the same holograms used to prevent counterfeiting, in notes and credit cards.

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The difference is that the meta-holographic structures are capable of showing one image when the incident light is in one direction, and another different image when the light is coming from the other direction.

In addition, the meta-holograms created now by a team at Pohang University in South Korea are thin and light, making them easier to apply in practice - they fall into the field of metamaterials , the same ones that manipulate light to create the mantles of invisibility.

Televisions and beam projectors can only transmit intensity of lights but holographic techniques can save light intensity and its phase information to play movies in three-dimensional spaces. At this time, if metamaterials are used, a user can change nano structures, size, and shapes as desired and can control light intensity and phase at the same time. Meta-hologram has pixel sizes as small as 300 to 400 nanometers but can display very high resolution of holographic images with larger field of view compared to existing hologram projector such as spatial light modulator.

Device illustration (left) and real images transmitted to one side and the other (right) - consider that the meta-surface is in the center of the black square.

To get ahead, the team used two different types of meta-surfaces - essentially flat metamaterials. The first meta-surface was designed to have phase information when the incident light is in the "forward" direction, while the other operates when the light is in the "back" direction.

As a result, different images are displayed in real time, depending on the direction of the light - or, in other words, transmitting different information to different locations.

In addition, the team applied dual magnetic resonances and antiferromagnetic resonances, which are phenomena occurring in silicon nanopillars, to nanostructure design to overcome low efficiency of the conventional meta-hologram. This newly made meta-hologram demonstrated diffraction efficiency higher than 60% (over 70% in simulation) and high-quality and clear images were observed.

Furthermore, the new meta-hologram uses silicon and it can be easily produced by following through the conventional semiconductor manufacturing process.

Junsuk Rho who is leading research on metamaterials said, 'Microscopic, ultrathin, ultralightweight flat optical devices based on a metasurface is an impressive technique with great potentials as it can not only perform the functions of the conventional optical devices but also demonstrate multiple functions depending on how its metasurface is designed. Especially, we developed a meta-hologram optical device that operated in forward and backward directions and it could transmit various visual information to multiple users from different locations simultaneously. We anticipate that this new development can be employed in multiple applications such as holograms for performances, entertainment, exhibitions, automobiles and more."


Article: Engineering spin and antiferromagnetic resonances to perform an efficient direction-multiplexed visible meta-hologram

Authors: Muhammad Afnan Ansari, Inki Kim, Ivan D. Rukhlenko, Muhammad Zubair, Selcuk Yerci, Tauseef Tauqeer, Muhammad Qasim Mehmood, Junsuk Rho

Magazine : Nanoscale Horizons

DOI: 10.1039 / D0NH90006K

Thursday, 6 February 2020

New type of symmetry discovered, hidden in artificial materials

Autodual symmetries emerge at critical points, causing two completely different materials to conduct sound in the same way.

It is not every day that you discover a new type of symmetry in nature.
Even less discover symmetries hidden in man-made artificial materials.
And the discovery has numerous immediate practical applications.

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A trio of researchers from the University of Chicago, USA, discovered a symmetry hidden inside the solids when using sound waves to study the interior of the materials. They used Lego blocks to build regular structures and assess how they react to sound.

What they found is that completely different structures can produce the same sound - something like hitting a green watermelon and a ripe watermelon and hearing the same sound.

"What excited us was the fact that we cannot explain our findings using existing concepts, such as spatial symmetries," said Professor Vincenzo Vitelli, recalling that physicists have used these concepts for decades to describe and predict the properties of an object with based on their spatial symmetries.

The new explanation that has emerged is what the researchers call "duality", a hidden symmetry associating apparently unrelated parts of the solid.

"We observed that pairs of distinct configurations along the mechanism have the same vibrational spectrum and related elastic modules. We demonstrated that these intriguing properties arise from a duality between pairs of configurations on both sides of a critical mechanical point," wrote the team. In other words, it is a self-duality, which emerges when a duality becomes recurrent in a periodic material.

In the past few years, there has been an explosion of interest in a field called metamaterials. These are artificial structures engineered to have characteristics not normally expected in nature. For example, much thought has gone into realizing an "invisibility cloak" using composite materials that bend incoming light around them by virtue of their internal geometry.

Fruchart and Vitelli imagined using this approach to take a particle such as a phonon—essentially a particle of heat—and give it properties that it doesn't usually have.

The discovery of this duality promises to have a great impact on the design of metamaterials , allowing to design artificial materials that have specific properties.

Most metamaterials have been designed to handle light, but this new symmetry paves the way for the design of artificial materials that manipulate sound - phonons, which are "particles of heat", rather than photons, particles of light.

Electrons have a property called "spin", which is used as the basis for some of the latest high-tech electronics. Phonons, in turn, do not have an intrinsic spin, but if it is possible to shape the structure of materials, it is possible to give phonons a "pseudo-spin". Vitelli and his colleagues called this concept "mechanical spintronics".

This would allow us to use these materials in phononic devices - similar to electronics, but with different skills, enabling phononics, or "heat electronics".

"Our approach also applies to other waves, not just phonons - for example, waves of light and matter," said researcher Michel Fruchart.


Article: Dualities and non-Abelian mechanics

Authors: Michel Fruchart, Yujie Zhou, Vincenzo Vitelli

Magazine: Nature

Vol .: 577, pages 636-640

DOI: 10.1038 / s41586-020-1932-6

Monday, 27 January 2020

Scientists create Crystal inside a crystal to improve screens and more

The beautiful patterns created by blue liquid phase crystals have a number of technological applications.

Liquid crystals have enabled new technologies, such as LCD screens, thanks to their ability to reflect certain wavelengths of light, or colors, and to be very easy to manipulate.

Researchers have now developed an innovative way to sculpt a crystal inside a liquid crystal.
Because these crystals within crystals can reflect light at certain wavelengths that others cannot, they can be used to improve screen and monitor technologies.

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They can also be manipulated with temperature, electrical voltage or chemicals, which makes them valuable for detection applications. Temperature changes, for example, would result in color changes. And since these changes require only small temperature variations or small voltages, the devices would consume very little energy.

Creating an interface between crystals

The molecular orientation of liquid crystals makes them useful in key functions of various display technologies. They can also form "blue phase crystals", in which the molecules are arranged in highly regular patterns, which reflect visible light.

To design a blue phase crystal interface, Xiao Li and his colleagues at the University of Chicago, USA, developed a method that is based on chemically patterned surfaces, on which liquid crystals are deposited, thus providing a means of manipulating their orientation molecular. This orientation is then amplified by the liquid crystal itself, allowing a specific blue phase crystal to be carved into another blue phase crystal.

The process, the result of theoretical predictions and experimentation to arrive at the right design, allowed the creation of specific crystal forms within the liquid crystals - something unprecedented.

Not only that: The newly sculpted crystal can be manipulated with temperature and electricity to change from a blue phase to another type of blue phase, thus changing color.

"This means that the material can change its optical characteristics very precisely," said Professor Juan de Pablo, from the Argonne National Laboratory. "We now have material that can respond to external stimuli and reflect light at specific wavelengths, for which we had no good alternatives before."

This ability to manipulate crystals on such a small scale also makes it possible to use them as models to manufacture perfectly uniform structures at the nanoscale.

Details of the manufacturing process and the interfaces inside the crystal.

Blue phase crystals

Blue phase crystals have the properties of liquids and crystals, which means that they can flow and are flexible, while having highly regular characteristics that transmit or reflect visible light.

They also have better optical properties and a faster response time than traditional liquid crystals, making them good candidates for optical technologies.

In addition, the projections responsible for reflecting light in the blue phase crystals are separated by relatively large distances compared to traditional crystals, such as quartz. The larger size of these projections facilitates the engineering of the interfaces between them, a process notoriously difficult in traditional crystalline materials.

These interfaces are important because they provide ideal locations for chemical reactions and mechanical transformations, and because they can make it difficult to transport sound, energy or light.


Article: Sculpted grain boundaries in soft crystals

Authors: Xiao Li, José A. Martínez-González, Orlando Guzmán, Xuedan Ma, Kangho Park, Chun Zhou, Yu Kambe, Hyeong Min Jin, James A. Dolan, Paul F. Nealey , Juan J. de Pablo

Magazine: Science Advances

Vol .: 5, no. 11, eaax9112

DOI: 10.1126 / sciadv.aax9112

Tuesday, 10 December 2019

The newly discovered Plastic hardens 1800 times on Heating

The soft, transparent gel at 25 ° C does not support weight (top), but quickly becomes rigid and opaque when heated to 60 ° C, becoming strong enough to support weight (bottom).

Heat hardening plastic

Researchers at Hokkaido University in Japan have developed a hydrogel that does the opposite of what polymer-based materials - such as plastic bottles - usually do: the material hardens when heated and softens when cooled.

The new material, which hardens 1,800 times when exposed to heat, could protect motorcyclists and race car drivers during accidents.

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Takayuki Nonoyama and his colleagues were inspired by how proteins remain stable within living things that survive in extreme heat environments, such as hot springs. Normally, heat "denatures" proteins, altering their structure and breaking their bonds. But proteins in thermophiles remain stable with heat, thanks to specially reinforced electrostatic interactions such as ionic bonds.

They mimicked this behavior by using a low-cost, non-toxic polyacrylic gel.

Phases of Polymers

The poly [acrylic acid] polyelectrolyte gel (PAAc) was immersed in an aqueous calcium acetate solution. PAAc itself behaves like any other polymer-based material, softening when heated. But when calcium acetate is added, the molecules of materials interact in a similar way to thermophilic proteins, causing PAAc to behave very differently.

As the temperature rises, the originally uniform gel separates into a dense polymer "phase" and a sparse polymer "phase." When it reaches a critical temperature of around 60 ° C, the dense phase undergoes severe dehydration, which strengthens ionic bonds and hydrophobic interactions between polymer molecules.

This causes the material to change rapidly from a soft, transparent hydrogel to a rigid, opaque plastic - 1,800 times stiffer, 80 times stronger and 20 times stronger than the original hydrogel.

Simply lowering the temperature causes the behavior to reverse, which opens up numerous possibilities for application.

Molecular structures and the mechanisms behind instant hydrogel thermal hardening.

Temperature sensitive intelligent materials

The team demonstrated one of the possible applications by combining the material with a fiberglass. The resulting composite fabric is soft at room temperature, but when it was rotated on an asphalt surface for five seconds at a speed of 80 km / hour, the heat generated by the friction was sufficient to harden the material with only minor abrasions. forming on the contact surface.

"Clothing made of similar fabric can be used to protect people during traffic accidents or sports, for example. Our material can also be used as a heat-absorbing window covering to keep indoors cooler," said Nonoyama.

"This polymeric gel can easily be made from versatile, inexpensive, non-toxic raw materials commonly found in everyday life. Specifically, polyacrylic acids are used in disposable diapers and calcium acetates are used in food additives. Our study contributes to basic research on new temperature sensitive polymers and applied research on intelligent temperature sensitive materials, "added Professor Jian Ping Gong.


Instant Thermal Switching from Soft Hydrogel to Rigid Plastics Inspired by Thermophile Proteins

Takayuki Nonoyama  Yong Woo Lee  Kumi Ota  Keigo Fujioka  Wei Hong  Jian Ping Gong

Advanced Materials 2019

A new type of artificial skin capable of self-regeneration

Research focused on the development of artificial skins could benefit both people with bioprostheses and robotics. In recent years, significant progress has been made in this direction, but none of the prototypes created to date have combined all the properties of human skin. This is today done. Recently, a team of Australian bioengineers has developed a new type of hydrogel that acts as an artificial skin and combines the strength, durability, flexibility and self-regeneration of human skin.

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This new hydrogel could be used as skin, tendon or muscle. " Thanks to the special chemistry we have incorporated into the hydrogel, it can repair itself after being damaged, as can human skin. Hydrogels are usually fragile, but our material is so strong that it could easily lift heavy objects. It can also change shape as human muscles do, "says chemist Luke Connal of the Australian National University.

The creation of a hydrogel that changes shape and has multiple functions has proven to be a permanent challenge for scientists, even with the natural inspiration of jellyfish, sea cucumbers and fly-flyers. While some hydrogels can withstand mechanical stresses, others have self-healing properties, and some have the ability to memorize shapes or change color.

An extremely reactive artificial skin

As far as UNA researchers know, no one else has been able to incorporate all these functions into one universal gel. By submitting their material to multiple tests, the authors claim to have created the first dynamic hydrogel that is solid, resistant to mechanical stresses, wear-resistant, self-healing and able to change shape and retain memory. The technical details have been published in the journal Advanced Materials.

Structure and preparation of the hydrogel. Credits: Zhen Jiang et al. 2019

Using this material, the researchers made extremely thin films of "flesh" without any breakage. When these films were heated or cooled, they then changed shape, bending one way or the other before returning to their original state with the right temperature.

Mechanical properties of the hydrogel: elasticity, strength, hardness. Credits: Zhen Jiang et al. 2019

Unlike many other hydrogels, which can sometimes take 10 minutes or more to change shape, this gel only takes 10 seconds to bend. Here, the key would be the dynamic hydrogen bonds of the gel and the imine (carbon-nitrogen) dynamic bonds, which work together to form "unprecedented properties".

Towards a more "human" robotics

Dynamic bonds have a high response to stimuli, making them perfect for environmental adaptation and self-healing, and imine bonds in particular have fast reaction kinetics that can allow rapid self-healing. . In addition, the authors claim that these materials can be easily prepared using simple chemistry, and if other polymers are added to the molecular mixture, perhaps even more functions can be achieved.

If the temperature is somehow used as a control, the authors think that this gel could one day be used as an artificial muscle. " In many sci-fi films, we see the most challenging work done by humanoid robots. Our research has taken an important step toward achieving this, "said materials engineer Zhen Jiang. In the meantime, the team hopes to turn their hydrogel into a printable 3D ink.


Tough, Self‐Healing Hydrogels Capable of Ultrafast Shape Changing

Zhen Jiang Broden Diggle India C. G. Shackleford Luke A. Connal

Volume31, Issue 48

Monday, 4 November 2019

Recycle heat to electricity with ultracentrifed liquids

 By circulating liquids in charged nanoscale channels, it is possible to convert heat into electricity as efficiently as the best thermoelectric materials.

When subjected to a temperature difference, a nanofluidic channel can generate electricity , with a performance comparable to that of the best thermoelectric solids.
© ILM (CNRS / University of Lyon 1)

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The materials solid thermoelectric can convert a temperature difference into electric energy . They thus constitute an important energy resource for the years to come. However, the best performing materials are rare, expensive and often toxic. Physicists of theInstitut light material in Lyon (. CNRS / University Lyon 1) explored an alternative possibility: using nanofluidic channels confining the water salty. Such systems have received much attention recently because they are able to produce electricity from the osmotic energy of seawater . This "blue energy" comes from the phenomenon of osmosis , that is to say the spontaneous flow of the liquid from the most concentrated to the least concentrated medium. But the application of these devices for recycling in heat electricity lost by many industrial processes in electricity is only beginning to be studied. This lower interest is explained by the standard image of the thermoelectricity of charged liquids, developed in the 1980s, and which predicted performance far below that of thermoelectric materials.

Scientists have tested these models using simulations of the behavior of matter at the atomic level. In this type of simulation, the motion of each atom is explicitly described, which allows to measure independently the influence of the various parameters (interactions with the walls, electrostatic contribution) on the movement of the atoms and therefore of the electric current.. Against all odds, they showed that the performance of nanofluidic systems was a hundred times better than the predictions of standard models, and could be comparable to those of the best thermoelectric solid materials. This work demonstrates the potential of nanofluidic systems, and by understanding their mechanisms, they can serve as a guide for the development of high performance devices, a cost-effective and non-toxic alternative to thermoelectric materials.


Monday, 21 October 2019

For the first time, fractal distributions have been demonstrated in a quantum material

Fractals are mathematical objects whose internal patterns are repeated, forming an invariant structure by scaling. From snowflakes to lightning, fractals are found in many natural phenomena. And recently, MIT researchers have demonstrated a fractal distribution of magnetic domains in a material with particular quantum properties.

MIT physicists provided the first known example of a fractal arrangement in a quantum material. The patterns have been observed in an unexpected distribution of magnetic units called "domains", which develop in a compound called nickel-neodymium oxide - a rare earth metal with amazing properties. The study was published in Nature Communications .

A better understanding of these areas and their structures could potentially lead to new ways of storing and protecting digital information. As the physicist Riccardo Comin explains, " the material is not magnetic at all temperatures ".

Geometric distribution of magnetic domains in nickel-neodymium oxide 

The atoms of nickel oxide and neodymium form minute clusters of magnetically oriented particles called domains. The domains come in different sizes and arrangements, depending on the quantum interactions between the electron s and their atoms under certain conditions. But the question was how they emerged in nickel-neodymium oxide, given its nature as a driver.

" We wanted to see how these areas appear and develop once the magnetic phase is reached when cooling the material, " says Comin. Researchers have in the past studied the unique magnetic properties of the material through X-rays. While this showed how the material was distributing its electrons at different temperatures, mapping the size and distribution of its domains under such conditions required more focused approach.

Experimental protocol used by researchers to analyze magnetic domain structures. Credits: Jiarui Li et al. 2019
" We have therefore adopted a special solution that focuses the X-ray beam, so that we can map, point by point, the arrangement of the magnetic domains in this material, " says Comin.

Fresnel lenses are stacked layers of transparent material with ridges, which redirect electromagnetic radiation. The lenses that Comin and his team developed were only 150 microns wide. The end result was an X-ray beam small enough to detect the fine scale of the magnetic domains through a thin neodymium nickel oxide film developed in the laboratory.

Fractal distribution of magnetic domains

Most of these areas were tiny. Scattered among them were bigger ones. But once the data was analyzed and a map was modeled, the distribution of larger domains among the many much smaller domains was strangely similar, regardless of the scale used.

Fractal distribution of magnetic domains in nickel-neodymium oxide. Credits: Jiarui Li et al. 2019

 The schema of the models was difficult to decipher at first, but after analyzing the statistics of the domain distribution, we realized that it had fractal behavior. It was completely unexpected, pure chance, "says Comin. Materials that can be used as both conductors and insulators already play an important role in the world of electronics. Transistors are based on this very principle.

But nickel-neodymium oxide has another property. The same fractal pattern of domains reappears when the temperature drops again, almost as if it had some sort of memory. " Similar to magnetic disks in rotating hard disks, we can consider storing bits of information in these magnetic domains, " concludes Comin.

Monday, 24 June 2019

Researchers found a way to restore sight of blind people using Orgnic Printing

One of the research leaders, Eric Glowacki, measures the electrical response of the neurostimulation devices to pulses of red light Photo credit: Thor Balkhed

A simple retinal prosthesis is being developed in collaboration between Tel Aviv University in Israel and LiU. Fabricated using cheap and widely-available organic pigments used in printing inks and cosmetics, it consists of tiny pixels like a digital camera sensor on a nanometric scale. Researchers hope that it can restore sight to blind people.

Researchers led by Eric Glowacki, principal investigator of the organic nanocrystals subgroup in the Laboratory of Organic Electronics, Linköping University, have developed a tiny, simple photoactive film that converts light impulses into electrical signals. These signals in turn stimulate neurons (nerve cells). The research group has chosen to focus on a particularly pressing application, artificial retinas that may in the future restore sight to blind people. The Swedish team, specializing in nanomaterials and electronic devices, worked together with researchers in Israel, Italy and Austria to optimise the technology.

Experiments in vision restoration were carried out by the group of Yael Hanein at Tel Aviv University in Israel. Yael Hanein’s group is a world-leader in the interface between electronics and the nervous system.

Photoactive material

The retina consists of several thin layers of cells. Light-sensitive neurons in the back of the eye convert incident light to electric signals, while other cells process the nerve impulses and transmit them onwards along the optic nerve to an area of the brain known as the “visual cortex”. An artificial retina may be surgically implanted into the eye if a person’s sight has been lost as a consequence of the light-sensitive cells becoming degraded, thus failing to convert light into electric pulses.

The artificial retina consists of a thin circular film of photoactive material, and is similar to an individual pixel in a digital camera sensor. Each pixel is truly microscopic – it is about 100 times thinner than a single cell and has a diameter smaller than the diameter of a human hair. It consists of a pigment of semi-conducting nanocrystals. Such pigments are cheap and non-toxic, and are commonly used in commercial cosmetics and tattooing ink.

“We have optimised the photoactive film for near-infrared light, since biological tissues, such as bone, blood and skin, are most transparent at these wavelengths. This raises the possibility of other applications in humans in the future,” says Eric Glowacki.

Microscopic donut

He describes the artificial retina as a microscopic doughnut, with the crystal-containing pigment in the middle and a tiny metal ring around it. It acts without any external connectors, and the nerve cells are activated without a delay.

“The response time must be short if we are to gain control of the stimulation of nerve cells,” says David Rand, postdoctoral researcher at Tel Aviv University. “Here, the nerve cells are activated directly. We have shown that our device can be used to stimulate not only neurons in the brain but also neurons in non-functioning retinas.”


Direct Electrical Neurostimulation with Organic Pigment Photocapacitors.
 David Rand, Marie Jakešová, Gur Lubin, Ieva Vėbraitė, Moshe David-Pur, Vedran Đerek, Tobias Cramer, Niyazi Serdar Sariciftci, Yael Hanein, Eric Daniel Głowacki.
 Advanced Materials, 2018; 1707292
DOI: 10.1002/adma.201707292

Thursday, 20 June 2019

Controlling Thermal Conductivity of Polymers with Light

Under ambient conditions or visible light (left side), the polymer is crystalline and has a high thermal conductivity. Once exposed to ultraviolet (UV) light (right side), the bond becomes a liquid of low thermal conductivity - the crystalline phase appears bright and the liquid phase appears dark. [Image: University of Illinois Materials Research Lab]

Heat control with light

The plastics capable of conducting heat are a recent class of new materials used in electronics and promise lighter cars .

The newest member of this family is a plastic that has its thermal conductivity controlled by light: Light can function as an optical switch, turning on and off the plastic's ability to conduct heat.

This means that this polymer will allow to route the heat on demand, taking it to where it is needed or removing it from where it is harmful.

"As far as we know, this is the first observation of a light-reversible reversible crystal-liquid transition in any polymer material." The particularly notable finding in this study is the rapid and reversible three-fold change in thermal conductivity associated with phase transition, said Jungwoo Shin of the University of Illinois, USA.

This possibility of optical control of the thermophysical properties of the polymer is due to the photoresponsive effect of the azobenzene molecule , which can be optically energized by visible light or by ultraviolet light.

"By synthesizing it with visible and visible UV light, we can change the shape of the azobenzene group by modulating the bond strength between the chains and producing a reversible transition between crystal and liquid," he said. Jaeuk Sung, a member of the team.

The next step will be to study the resilience of the polymer under various operating conditions, to define its possible uses.


 Light-triggered thermal conductivity switching in azobenzene polymers
Jungwoo Shin, Sung Jaeuk, Minjee Kang, Xu Xie, Byeongdu Lee, Kyung Min Lee, Timothy J. White, Cecilia Leal, Nancy R. Sottos, Paul V. Braun, David G Cahill
 Proceedings of the National Academy of Sciences
 DOI: 10.1073 / pnas.1817082116

Bulletproof wood now also fire resistant

The flame retardant effect is generated by the formation of a layer of charcoal on the surface of the wood subjected to fire. [Image: Wentao Gan et al. - 10.1002 / adfm.201807444]

Anti-fire wood

The creators of bulletproof wood have taken yet another surprising step to make wood a competitor to the height of synthetic materials.

Wentao Gan and his colleagues at the University of Maryland, USA, have concluded that their superdurated wood is extremely fire-resistant.

They have discovered how to use a chemical compound to soften the wood, allowing it to be compressed, removing the spaces between the cell walls.

When subjected to fire, this compressed wood forms a protective layer of coal on its surface, which prevents fire from spreading and preserves the internal structural integrity of the wood.

In other words, in addition to not burning readily, the wood structure does not collapse, as occurs with ordinary wood constructions.

The effects of the treatment are dramatic in terms of resistance to burning. [Image: Wentao Gan et al. - 10.1002 / adfm.201807444]

Fire-resistant wood

There are already techniques to make the wood more resistant to fire by means of chemical treatments. But these techniques are expensive and far from being environmentally friendly, as they involve injection into the wood of halogenated flame retardants or coatings of inorganic nanoparticles. Also, the wood does not get strong enough.

The treatment to make fire-resistant wood is virtually the same as used to make the superdurated wood presented by the team last year.

In tests, the ignition timing of the wood doubled, while its heat release was reduced by more than a third.


 Dense, Self-Formed Char Layer Enables a Fire-Retardant Wood Structural Material

Wentao Gan, Chaoji Chen, Zhengyang Wang, Jianwei Song, Yudi Kuang, Shuaiming He, Ruiyu Mi, Peter B. Sunderland, Liangbing Hu
 Advanced Functional Materials 
 DOI: 10.1002 / adfm.201807444

Tuesday, 18 June 2019

Metamaterial revolutionizes magnetic resonance imaging (MRI) and medical imaging

Prototype of the cylinders that form the metamaterial. [Image: Duan et al. - 10.1038 / s42005-019-0135-7]

Metamaterial for exams

The metamaterials , which began as a mathematical curiosity and soon proved even more curious, by enabling the creation of invisibility cloaks , are already ready to improve medical examinations.

A team at Boston University in the United States created a magnetic metamaterial in the form of a small cylinder that proved capable of strongly amplifying the signals from MRI machines.

The result is a much sharper examination done in half the time of the current examinations and still allowing to use a much lower magnetic field, possibly paving the way for the production of lower cost and lower cost equipment.

Magnetic Metamaterial

The magnetic metamaterial consists of a series of units called helical resonators, structures three centimeters high created from plastic printed in 3D and copper coils.

The small devices alone do not impress. However, when placed together, the helical resonators form a flexible matrix, malleable enough to cover the patella, abdomen, head, or any part of the body that needs imaging.

When the array is placed close to the body, the resonators interact with the machine's magnetic field, increasing the signal-to-noise ratio of the MRI, "increasing the volume of the image," as the researchers say.

"The 'magic' part is the design and the idea," said researcher Guangwu Zhang. "Many people are surprised by its simplicity.

Comparison of the MRI scans of 1.5 T with and without the magnetic metamaterial. [Image: Duan et al. - 10.1038 / s42005-019-0135-7]

Next generation magnetic resonance imaging

To test the magnetic set, the team examined chicken legs, tomatoes and grapes using a 1.5 Tesla machine. The magnetic metamaterial produced a 4.2-fold increase in the signal-to-noise ratio, a radical improvement, which means that lower magnetic fields could be used to take clearer images than is currently possible.

Researchers now hope to partner with the industry so their magnetic metamaterial can be adapted to real-world clinical applications.


Boosting magnetic resonance imaging signal-to-noise ratio using magnetic metamaterials
Guangwu Duan, Xiaoguang Zhao, Stephan William Anderson, Xin Zhang
Communications Physics
Vol. 2, Article number: 35
DOI: 10.1038 / s42005-019-0135-7

Wednesday, 12 June 2019

New Developed Fiber is as Flexible as Elastic But Tough as Steel

Metal-rubber composite

Researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal.

The resulting composite is a sturdier material that can be incorporated into lightweight robotics, packaging materials, next generation textiles and even in biomedical applications.

"A good way to explain the material is to think of elastics and metal wires.An elastic can stretch a lot, but it does not take much force to stretch it.A metal wire requires a lot of force to be stretched, but it does not take much "Our fibers have the best of these two worlds," explained Professor Michael Dickey, of the State University of North Carolina, USA.

The fibers consist of a metal core of gallium encased by an elastic polymer coating.

When placed under stress, the fiber has the strength of the metal core. But when the force is too much and the metal breaks, the fiber does not break - the polymer coating absorbs the tension between the broken metal parts and transfers the voltage back to the still intact parts of the metal core.

"Every time the metal core breaks, it dissipates energy, allowing the fiber to continue to absorb energy as it stretches," explained Dickey. "Instead of splitting in two when stretched, it can stretch up to seven times the original length before breaking, which happens while many additional breaks in the yarn are generated along the way."

Tenacity of the skin

The fiber response is similar to the way human connective tissue is maintained when a bone breaks.

"There is a lot of interest in engineering materials to mimic the tenacity of the skin - and we have developed a fiber that has overcome the tenacity of the skin and is still elastic like the skin," said Dickey.

The fibers can be reused by melting the metal cores again - gallium fuses at a mere 30 ° C, which means that the polymer is not affected.

"This is just a proof of concept, but it has a lot of potential. We are interested to see how these fibers could be used in light robotics or when woven into fabrics for various applications," said Dickey. 

Toughening stretchable fibers via serial metal fracturing Christopher B. Cooper, Ishan D. Joshipura, Dishit P. Parekh, Justin Norkett, Russell Mailen, Victoria M. Miller, Jan Genzer, Michael D. Dickey Science Advances Vol .: 5, no. 2, eaat4600 DOI: 10.1126 / sciadv.aat4600

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