Lună: martie 2018

Midwest Industries MI M-LOK Sistem de protectie manuala / feroviar tactil pentru FN M249 LMG / SAW!(Midwest Industries MI M-LOK Tactical Handguard/Rail System for FN M249 LMG/SAW)

Primul lucru pe care l-am aratat la standul lor SHOT Show 2018 este noul sistem de protectie manuala / feroviar MI L-LOK pentru FN M249 LMG / SAW pentru montarea tuturor accesoriilor (manere verticale, lumini albe tactice si iluminatoare infrarosu, lasere , etc.), care vă permite încă să pliați mânerul în poziția în jos și să pliați un suport bi-pod, tri-pod sau altul. Este compatibil cu trepiedele M122, M192 și suporturile Pintle. Este destul de slick, după cum puteți vedea în filmul lui DR de mai jos, și este făcut chiar aici în SUA. Deci, e Berry Compliant

Midwest Industries MI M-LOK Tactical Handguard/Rail System for FN M249 LMG/SAW! (Video!)

Posted by: David Crane March 22, 2018

DefenseReview’s (DR) done quite a bit of reporting on Midwest Industries (MI) products (see “Related Articles” section below), and for good reason. They work, they look good, they’re high-quality, and they’re priced correctly. Basically, they’re awesome. So, we always make sure to stop by their booth at SHOT Show to check out the latest and greatest.

The first thing we were shown at their booth at SHOT Show 2018 is the new MI L-LOK Tactical Handguard/Rail System for the FN M249 LMG/SAW for mounting all your accessories (vertical fore grips, tactical white lights and infrared illuminators, lasers, etc.), and still allowing you to fold carry handle in the down position, and fold a bi-pod, tri-pod or other mount. It’s compatible with M122, M192 tripods and Pintle mounts. It’s pretty slick, as you can see in DR’s video below, and it’s made right here in the USA. So, it’s Berry Compliant.

Here’s all the detailed info on it, right fromt the Midwest Industries website:

“- Simple installation that requires zero modifications
– All installation hardware and tools are included for installation that can be done in the field
– Constructed of 6061 aluminum hard coat anodized and blackened stainless screws for corrosion resistance
– A faceted bottom shape for a great ergonomic feel
– A rock solid modular mounting platform for lights and laser aiming devices
– Includes two MI aluminum M-Lok rail sections
– Allows the use of a forward vertical grips
– Does not interfere with multiple barrel change
– Can still be used with M122, M192 tripods and Pintle mounts
– Allows carry handle to be folded in the down position
– Allows for bipod to be folded and locked
– Features 29 full M-Lok slots and 2 half slots
– Dimensions: Length 7.625 Width 3.400 Weight 11.7 oz
– 100% made in the U.S.A.”

 

Company Contact Info:

Midwest Industries, Inc (MI)
W292S4498 Hillside Rd.
Waukesha, WI 53189
Phone: 262-896-6780
Email Contact Page: http://www.midwestindustriesinc.com/index.cfm?fuseaction=page.display&page_id=33
Website: http://www.midwestindustriesinc.com

Scotând știința fundamentală a senzorilor(Sniffing out the foundational science of sensors)

Acest senzor poate detecta metanul la concentrații mult mai scăzute decât cele actuale.
În viitor, oamenii de știință ar putea să combine diferite materiale 2D în senzori subțiri și versatil. „Frumusețea materialelor 2D este că puteți să strângeți diferitele straturi împreună pentru a crea materiale artificiale”, a declarat Kai Xiao, om de știință ORNL. Aceste materiale artificiale ar putea detecta o varietate de substanțe chimice diferite, în loc de una singură.Acest senzor sa îmbunătățit atât de mult pe tehnologia existentă încât, în 2016, revista R & D 100 a recunoscut-o ca fiind un finalist în R & D 100. Echipa de cercetare lucrează acum cu proiectul Array of Things, o colaborare între Universitatea din Chicago și ANL. Ca parte a efortului de a colecta date în timp real de la sute de senzori din Chicago, echipa Array of Things anticipează utilizarea acestor senzori de metan în viitor.
Proiecte precum „Array of Things” au potențialul de a transforma orașele în rețele de senzori, plasând ochii și nasul digital pe întregul peisaj construit. Dar aceste rețele și tehnologii nu ar fi posibile fără o bază științifică solidă.

Posted: Mar 22, 2018

Sniffing out the foundational science of sensors

(Nanowerk News) The human nose can distinguish among a trillion different combinations of smells. Even so, there are plenty of gases that our noses can’t detect at the level of sensitivity we need. That’s where gaseous sensors come in. While some of the first sensors were animals – like canaries in coal mines – we’ve since replaced them with technologies that can detect miniscule amounts of chemicals in the air.
Just like our own noses, gaseous sensors are essential for safety and comfort. In factories, gaseous sensors can alert managers to chemical leaks or processes running incorrectly. Outside, they measure pollutants, helping cities monitor air quality. In homes, they keep family members safe. Building managers use measurements from humidity and temperature sensors to maximize energy efficiency.
These sensors wouldn’t exist without a fundamental understanding of chemistry and physics. This basic knowledge helps scientists understand how and why sensing materials interact with gaseous chemicals. Many cutting-edge materials have promise for use in sensors, if only scientists can learn how to better produce and control them.
methane sensor
This sensor can detect methane at much lower concentrations than current ones. It relies on nanotechnology developed at the Center for Nanoscale Materials. (Image: Ralu Divan, Argonne National Laboratory)
„Sensors are where materials research meets environmental detection,” said Pete Beckman, a researcher at Department of Energy’s Argonne National Laboratory (ANL).
To set the groundwork for innovation, the DOE Office of Science funds projects and user facilities that support sensors research.

Creating the Materials for Sensing
Like noses, sensors rely on a combination of components to detect and make sense of gases or chemicals in the air. In humans, molecules float up into your nose and bind to special neurons. Neurons then pass the message up to the brain. In sensors, the material inside the sensor acts as a neuron. When that material interacts with a chemical in the air, it may emit light, change its ability to conduct electricity, or shift shape. The materials and electronics around the sensing material communicate that message to the sensor’s „brain,” whether that brain is a computer or a warning signal like a siren.
Developing sensors’ nervous systems and brains is a job for applied science. Fundamental research like the work at the Office of Science’s laboratories sets the foundation for that applied science. In particular, this research is expanding scientists’ understanding of the materials themselves and how to produce them.
Three types of cutting-edge materials offer huge potential for use in sensors: nanoparticles, two-dimensional (2D) materials, and metal-organic frameworks (MOFs). Nanoparticles are miniscule particles that are bigger than atoms, but act fundamentally differently from larger particles of the same substance. 2D materials, like graphene, form sheets only a single atom thick. MOFs are compounds made of metal ions linked together by carbon-based connectors.
All of these materials have humongous surface areas compared to their overall sizes. Because lots of gas molecules can interact with their surfaces, they can be sensitive to tiny amounts of chemicals. In addition, scientists can craft all of these materials into a variety of structures. That customization could allow researchers to create specialty materials to detect a particular chemical.
Zinc Sulfide Nanoparticles
The key to building a better sensor may lie in making its sensing material out of nanoparticles. Unfortunately, it’s challenging to manufacture some of the most promising of those nanoparticles. Sensors for hydrogen and other gases already use the material zinc sulfide. Producing zinc sulfide in nanoparticle form could make it cheaper and more effective. But the current process for producing zinc sulfide nanoparticles involves very high temperatures, pressures, and toxic chemicals.
Scientists at DOE’s Oak Ridge National Laboratory (ORNL) investigated a cheaper, more efficient nanoparticle production process. Researchers supported by both DOE’s Advanced Manufacturing Office and Office of Science found that microbes may offer an alternative path forward („A large-scale technique to produce quantum dots”).
Not just any bacteria will do. Scientists used Thermoanaerobacter, a bacteria that normally lives in extremely hot places with no oxygen. After adding a cheap sugar and chemicals that included zinc and sulfur, the bacteria produced about three-quarters of a pound of zinc sulfide nanoparticles. The process was 90 percent cheaper than current methods.
Growing 2D Materials
2D materials are a special form of nanomaterial that are only a few atoms thick. They have so much surface area compared to their volume that they provide a lot of space for gas molecules to interact and are able to hold a large number of them. But 2D materials act so differently from their normal „bulk” counterparts that scientists don’t have a good grasp on how they grow. Without this understanding, manufacturers can’t consistently produce high-quality versions of them.
To tackle this problem, ORNL scientists explored a better way to grow 2D material gallium selenide (GaSe) (JACS, „Edge-Controlled Growth and Etching of Two-Dimensional GaSe Monolayers”). As they grew the material in a container filled with argon gas, they found that by changing the temperature and flow of the gas, they could switch back and forth between laying down and taking away atoms. But just discovering how to change back and forth between the two states didn’t tell them what was actually happening on the chemical level.
„To visualize what we were doing in the lab, we needed high-resolution, state-of-the-art facilities as well as in-situ diagnosis tools,” said Tolga Aytug, an ORNL scientist. To get that level of precision, the team turned to the Center for Nanophase Materials Sciences, an Office of Science user facility at ORNL. The tools there helped them see how the processes they used to grow the material affected its structure and properties. Based on that information, they refined their methods to get the characteristics they wanted.
In the future, scientists may be able to combine various 2D materials into thin, versatile sensors. „The beauty of 2D materials is that you can stack the different layers together to make some artificial material,” said Kai Xiao, an ORNL scientist. These artificial materials would be able to detect a variety of different chemicals instead of just a single one.
Metal-Organic Frameworks
The metal ions and carbon-based connectors of MOFs form open, cage-like structures. A MOF only a few inches wide has an amazing 2.5 acres of surface area. That provides plenty of space for molecules to interact with.
As a result, MOFs can sense minute levels of chemicals. Scientists control which chemicals they want a MOF to detect by changing the size of its spaces, its shape, or how its parts link to each other.
„For a MOF-based sensor to work, it has to be very selective and very sensitive,” said Praveen Thallapally, a scientist at DOE’s Pacific Northwest National Laboratory (PNNL).
One benefit specific to MOFs is their ability to accommodate new molecules by changing their structures. PNNL scientists found a MOF with a zinc base could capture cobalt and copper. When these metals exited the molecule, the MOF returned to its original structure. This means after a chemical attaches to a MOF and triggers a sensor, someone could reset and reuse the sensor without needing to replace the MOF.
Much of the ongoing research into MOFs focuses on how to discover and build them. MOFs’ traditional starting materials are rigid and difficult to work with. In contrast, polymers (flexible chains of molecules) are easier to control. However, they usually bunch together in dense, disorganized clumps. To draw on the advantages of each, scientists from the University of California, San Diego found a way to use polymers to build MOFs („Novel porous materials made from flexible ‘spaghetti-like’ molecules„). Using both allows researchers to combine MOFs’ consistency and large surface area with polymers’ ease of use. The researchers used the hybrid materials to create thin films, which are typically used in sensors.
The next breakthrough in MOF research may come from computer modeling. Using trial and error to figure out which structure will interact best with a specific chemical could take years and be very expensive. In contrast, powerful computer models using machine learning allow scientists to find just the right material in a few days.
PNNL scientists searching for a MOF that could select between xenon and krypton collaborated with the National Energy Research Scientific Computing Center, an Office of Science user facility at DOE’s Lawrence Berkeley National Laboratory. After searching through more than 120,000 options, their computer model pointed to a calcium-based material that excelled at this task.

Connecting the Nose to the Body
A great sensing material is essential, but it won’t work by itself. Just as a nose needs a body and brain, sensing materials need to be part of a bigger mechanism. Unfortunately, getting these materials to work together within a sensor is often a challenge.
Printing Nanoparticle Ink
„Ink” made of sensing nanoparticles printed onto paper, plastic, rubber, or fabric could allow engineers to create smaller and more flexible sensors.
„Making particles is one thing. But from those particles, making a functional ink is not trivial,” said ORNL scientist Pooran Joshi, in a slight understatement.
One ORNL study (ACS Applied Materials & Interfaces, „Low-Thermal-Budget Photonic Processing of Highly Conductive Cu Interconnects Based on CuO Nanoinks: Potential for Flexible Printed Electronics”) tackled the best way to turn copper-based nanoparticles into high-quality ink. By shining a high-intensity light for only a few millionths of a second, scientists fused the nanoparticles together without melting the surface underneath. When the copper-based nanoparticle ink fused together, it created a printed surface. Researchers then used the printed surface as a component in a temperature sensor.
Combining Nanotubes and Nanocrystals
Scientists know that sensors made of nanotubes and nanocrystals could detect as little as one part per million of a gas – if only they can get these two materials to work together.
Ralu Divan and her team at ANL discovered a way to add nanocrystals of zinc oxide – which is already used in sensors – to carbon nanotubes. Sensors that use the two together could be far more sensitive to methane than current technology. By placing the zinc oxide nanocrystals down atom by atom, they created a thin, consistent layer on top of the nanotubes. With this process, companies can precisely control the zinc oxide’s thickness and coverage.
To examine the bonds between the nanocrystals and nanotubes, the team relied on the Center for Nanoscale Materials, an Office of Science user facility at ANL. „Having everything in one place has saved a lot of time and we were able to move faster than we expected,” said Divan.
As a result, they developed a sensor that could detect much lower concentrations of methane than previous ones. Operators can use it again in seconds instead of minutes or hours.
This sensor improved so much on the existing technology that in 2016, R&D 100 Magazine recognized it as an R&D 100 finalist. The research team is now working with the Array of Things project, a collaboration between the University of Chicago and ANL. As part of the effort to collect real-time data from hundreds of sensors across Chicago, the Array of Things team anticipates using these methane sensors in the future.
Projects such as the Array of Things have the potential to transform cities into networks of sensors, placing digital eyes and noses throughout the built landscape. But these networks and technologies wouldn’t be possible without a solid scientific foundation. Nothing may match the human nose’s versatility, but research the Office of Science is supporting helps fill in the gaps of our biological capabilities.
Source: U.S. Department of Energy, Office of Science

Materiale 2D pentru nanoelectronica aerosolizabilă(2D materials for aerosolizable nanoelectronics)

cercetatorii descriu o noua casatorie de materiale, combinand electronica ultra-rapida 2-D cu particule miniaturate pentru a crea masini microscopice.O proprietate neexplorată de aici a materialelor electronice 2D, cum ar fi grafenul, nitrura de bor hexagonală și MoS 2, este capacitatea de a grefa circuite electronice, tranzistori, memorie și senzori pe particule coloidale. Astfel de particule pot accesa hidrodinamica locală în fluide pentru a împărtăși motilitatea și pot accesa în alt mod spații inaccesibile pentru electronica convențională. Aici vom dezvolta o abordare a transferului de materiale 2D, combinată cu litografia convențională, cu circuite funcționale completate, pe particule SU-8 (100x100x1 μm 3 ) care funcționează ca mașini de stat complet autonome.

Posted: Mar 21, 2018

2D materials for aerosolizable nanoelectronics

(Nanowerk News) Tiny floating robots could be useful in all kinds of ways, for example, to probe the human gut for disease or to search the environment for pollutants. In a step toward such devices, researchers describe a new marriage of materials, combining ultrathin 2-D electronics with miniature particles to create microscopic machines.
The researchers will present their work today at the 255th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 13,000 presentations on a wide range of science topics.
A schematic diagram of a microscopic chemical detection machine depicting a micrometer-sized polymer particle coated with a nanoelectronic circuit
A schematic diagram of a microscopic chemical detection machine depicting a micrometer-sized polymer particle coated with a nanoelectronic circuit. (Image: Michael Strano)
„You can make electronic circuits that are a single atom thick, which is just insanely thin,” Michael Strano, Ph.D., says. „One creative use no one has thought of until now is taking these electronics and grafting them onto a colloidal particle. The particle, which can float in the air like a speck of dust, has simple computing functions. You can bring these new electronics to environments they otherwise could not access.”
As a first step, the researchers needed to develop a compatible set of electronic components for the particle’s coating to form a closed autonomous circuit. „This was difficult to do,” says Volodymyr Koman, Ph.D., a research fellow in Strano’s group at Massachusetts Institute of Technology. „We went through a number of different devices to meet certain power and energy requirements.”
In the end, Strano’s team selected a biocompatible material, SU-8, for the micrometer-sized particles and lithographically etched them to create a closed circuit consisting of a power source, a detector and a memory device. The power source was a p-n heterojunction of MoS2 and WSe2that can convert light into electric current. Both MoS2 and WSe2 are 2-D semiconductors. The detector was a chemiresistor, a distinct single layer of MoS2, designed to change its electrical resistance in response to an environmental agent. The electrical output is stored in a memory device consisting of a separate layer of MoS2 flakes sandwiched between gold and silver electrodes.
Since particle mobility and stability would be an important part of the proposed applications, the researchers first checked whether and how far the electronic particles could travel. Importantly, 2-D materials possess higher strain limits as compared to similar materials. The researchers aerosolized them and propelled them toward a target; the tiny particles flew a couple of feet.
The researchers envision a range of uses for these miniature flying machines. Monitoring large areas for bacteria, spores, smoke, dust or toxic fumes currently requires enormous resources, Koman says. Satellites or a fleet of flying drones can do these tasks but they are expensive, while on-the-ground sensors require labor-intensive installation, which is often slow in comparison to the aerosol spreading velocity. „As an alternative, we introduce the concept of an aerosolizable electronic device,” he says. As one example, the researchers tested the tiny devices in a simulated gas pipeline. The flying machines successfully sailed through the test chamber and detected the presence of carbon particulates or volatile organic compounds along the way and stored this information in memory.
„We put small retroreflectors on the particles – like you have on your bicycles – so they reflect light and allow us to rapidly find the particles,” Koman says. After capture, the researchers downloaded the information from the particles. „For readout, the particles have designated metallic connections, like a socket: Once you insert two probes, you can read out the device’s state.” The memory can then be wiped so the miniature machines can be reused.
The researchers’ next steps are to develop particles for additional applications, including as monitors of the human digestive system. „This is the right idea and the right time,” says Strano. „Think of these as proto-robots.”
Presentation: Colloidal, Nanoelectronic State Machines Based on 2D Materials for Aerosolizable Electronics

Abstract
A here-to-fore unexplored property of 2D electronic materials such as graphene, hexagonal boron nitride and MoS2 is the ability to graft electronic circuits, transistors, memory and sensors onto colloidal particles. Such particles can access local hydrodynamics in fluids to impart motility and can otherwise access spaces inaccessible to conventional electronics. Herein, we develop a 2D material transfer approach combined with conventional lithography to pattern completed, functional circuits on SU-8 particles (100x100x1 µm3) that function as fully autonomous state machines. The circuits are powered by a p-n heterojunction of MoS2 and WSe2 operating as a photodiode, which powers, as a chemiresistor circuit element, a distinct MoS2monolayer for the detection of VOCs or carbon particulates. Finally, the electrical output is irreversibly stored in a memristor device placed in series consisting as a distinct MoS2 flake sandwiched between Au and Ag electrodes and protected from the environment by hBN monolayer. These colloidal state machines are capable of operation after aerosolization and hydrodynamic propulsion to a target over 0.6 m away. The devices can successfully detect the presence of select analytes while aerosolized, storing this information in memory on the particle for retrieval upon capture. An incorporated retroreflector design of the system allows for facile position location using optical detection. Such state machines, enabled by 2D nanoelectronics, may find widespread application as probes in the human digestive tract, oil and gas conduits, chemical and biosynthetic reactors, and as autonomous environmental sensors.
Source: American Chemical Society

Celulele de nucă de celuloză au câștigat de la gunoi de grajd și de vacă pentru hârtia durabilă(Cellulose nanofibers won from elephant and cow manure for sustainably making paper)

Demonstrăm faptul că, prin purificarea chimică a gunoiului de grajd, se poate izola celuloza microfibrilată cu proprietăți controlabile. Fibrele au fost caracterizate în ceea ce privește conținutul lor de celuloză și proprietățile fizico-chimice pentru a optimiza procesul de extracție. Fibrele optimizate au fost inițial utilizate pentru prepararea hârtiilor care au fost caracterizate în ceea ce privește proprietățile lor fizico-chimice și mecanice și au servit drept material de referință. Mai mult, fibrilele au fost ulterior rafinate mecanic și hârtiile produse din aceste nanofibrili rafinate de gunoi de grajd, care au fost comparate cu hârtia elefantă de gunoi de grajd și cu nanoparagii de celuloză.

Posted: Mar 21, 2018

Cellulose nanofibers won from elephant and cow manure for sustainably making paper

(Nanowerk News) It’s likely not the first thing you think of when you see elephant dung, but this material turns out to be an excellent source of cellulose for paper manufacturing in countries where trees are scarce, scientists report. And in regions with plenty of farm animals such as cows, upcycling manure into paper products could be a cheap and environmentally sound method to get rid of this pervasive agricultural waste.
The researchers are presenting their results today at the 255th National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world’s largest scientific society, is holding the meeting here through Thursday. It features more than 13,000 presentations on a wide range of science topics.
Elephant and Cow Manure for Making Paper Sustainably
Paper (top) can be made from cellulose derived from elephant manure (bottom). (Image: Kathrin Weiland)
The idea for the project germinated on Crete, where Alexander Bismarck, Ph.D., noticed goats munching on summer-dry grass in the small village where he was vacationing. „I realized what comes out in the end is partially digested plant matter, so there must be cellulose in there,” he recalls.
„Animals eat low-grade biomass containing cellulose, chew it and expose it to enzymes and acid in their stomach, and then produce manure. Depending on the animal, up to 40 percent of that manure is cellulose, which is then easily accessible,” Bismarck says. So, much less energy and fewer chemical treatments should be needed to turn this partially digested material into cellulose nanofibers, relative to starting with raw wood, he conjectured.
After working with goat manure, Bismarck, who is at the University of Vienna, Austria, his postdoc Andreas Mautner, Ph.D., and graduate students Nurul Ain Kamal and Kathrin Weiland moved on to dung from horses, cows and eventually elephants. The supply of raw material is substantial: Parks in Africa that are home to hundreds of elephants produce tons of dung every day, and enormous cattle farms in the U.S. and Europe yield mountains of manure, according to Mautner.
The researchers treat the manure with a sodium hydroxide solution. This partially removes lignin – which can be used later as a fertilizer or fuel – as well as other impurities, including proteins and dead cells. To fully remove lignin and to produce white pulp for making paper, the material has to be bleached with sodium hypochlorite. The purified cellulose requires little if any grinding to break it down into nanofibers in preparation for use in paper, in contrast to conventional methods.
„You need a lot of energy to grind wood down to make nanocellulose,” Mautner says. But with manure as a starting material, „you can reduce the number of steps you need to perform, simply because the animal already chewed the plant and attacked it with acid and enzymes. You inexpensively produce a nanocellulose that has the same or even better properties than nanocellulose from wood, with lower energy and chemical consumption,” he says.
The dung-derived nanopaper could be used in many applications, including as reinforcement for polymer composites or filters that can clean wastewater before it’s discharged into the environment, Bismarck says. His team is working with an industrial consortium to further explore these possibilities. The nanopaper could also be used to write on, he says.
The researchers are also investigating whether the process can be made even more sustainable, by first producing biogas from manure and then extracting cellulose fibers from the residue. Biogas, which is mostly methane and carbon dioxide, can then be used as a fuel for generating electricity or heat.
Presentation: Cellulose Nanopapers from Elephant Manure

Abstract
The interest in cellulose fibres, in particular micro- or nanofibrillated cellulose, utilized in paper and composite materials as alternative to conventional fibre materials, has recently grown significantly. Thereby, particularly in countries without access to large forest areas, an alternative to wood as raw material for natural fibres is highly desirable. In order to promote an environmentally sustainable, widely available and cheap raw material, elephant manure was proposed as potential source. As elephants digest only 30 to 40% of their diet, their manure contains large quantities of fibrous cellulosic material. In addition, the mechanical, acidic and enzymatic pre-treatment during ingestion and digestion initiates break down of the fibres. This makes this animal waste a suitable candidate for the use as precursor for the production of micro- or even nanofibrillated cellulose. Nanocelluloses are commonly prepared by mechanical disintegration of plant material, optionally with chemical pre-treatment, thus requiring a lot of energy and chemicals during the fibrillation process. Therefore, utilizing the elephant as the first-stage bioreactor for the defibrillation of cellulose fibres by mechanical and chemical means would constitute an energy-efficient approach.
We demonstrate that by chemical purification of elephant manure, microfibrillated cellulose with controllable properties can be isolated. The fibrils were characterized regarding their cellulose content and physico-chemical properties in order to optimize the extraction process. Optimized fibrils were initially used for the preparation of papers that were characterized regarding their physico-chemical and mechanical properties and served as reference material. Moreover, the fibrils were further mechanically refined and papers produced from these refined elephant manure nanofibrils that were compared to the non-refined elephant manure papers and cellulose nanopapers.
Source: American Chemical Society

Proiectarea unui material nou pentru îmbunătățirea ecografiei(Designing a new material for improved ultrasound)

Dezvoltarea unei baze teoretice pentru piezoelectricitatea ultrahighi in materialele feroelectrice a condus la un material nou cu dubla reactie piezoasa a oricarui ceramica feroelectrica comerciala existenta,Piezoelectricitatea este proprietatea materială în centrul ultrasunetelor medicale, al sonarului, al controlului activ al vibrațiilor și al multor senzori și actuatori. Datorită polarizării spontane, un material piezoelectric are capacitatea de a se deforma mecanic atunci când este aplicată o tensiune electrică sau de a genera sarcină electrică atunci când se aplică o forță mecanică.

Posted: Mar 21, 2018

Designing a new material for improved ultrasound

(Nanowerk News) Development of a theoretical basis for ultrahigh piezoelectricity in ferroelectric materials led to a new material with twice the piezo response of any existing commercial ferroelectric ceramics, according to an international team of researchers from Penn State, China and Australia.
Piezoelectricity is the material property at the heart of medical ultrasound, sonar, active vibration control and many sensors and actuators. Due to spontaneous polarization, a piezoelectric material has the ability to mechanically deform when an electric voltage is applied or to generate electric charge when a mechanical force is applied.
Adding small amounts of a carefully selected rare earth material, samarium, to a high-performance piezoelectric ceramic called lead magnesium niobate-lead titanate (PMN-PT) dramatically increases its piezo performance, the researchers report in Nature Materials(„Ultrahigh piezoelectricity in ferroelectric ceramics by design”). This materials-by-design strategy will be useful in designing materials for other applications as well, the team believes.
A long-range ferroelectric domain with nanoscale structure heterogeneity is evidenced by high-resolution TEM
A long-range ferroelectric domain with nanoscale structure heterogeneity (4-8 nm) is evidenced by high-resolution TEM. (Image: Fei Li/Penn State)
“This is not the typical way to develop new materials,” said the team’s co-corresponding author, Long-Qing Chen, Donald W. Hamer Professor of Materials Science and Engineering, professor of mathematics and professor of engineering science and mechanics, Penn State. “The majority of existing useful materials are discovered by trial and error experiments. But here we designed and synthesized a new piezoelectric ceramic guided by theory and simulations.”
The team first analyzed the impact of adding various chemical dopants on the local structure of an existing ferroelectric ceramic. They were then able to select the most effective dopants by comparing the measured dielectric losses with the signatures obtained from phase-field simulations. After the screening of dopants, they then focused on the processing and composition optimization to achieve the ultrahigh piezoelectricity.
“This work is based on an understanding of the origin of ultrahigh piezoelectricity in the ferroelectric crystals that were developed 30 years ago. Our new understanding suggested that local structure heterogeneity plays an important role in piezoelectricity in ferroelectrics, which also can be extended to other functionalities,” said co-corresponding author Shujun Zhang, a professor of materials science formerly at Penn State and now at the University of Wollongong in Australia,
Local structure heterogeneity refers to nanoscale-size structural distortions within a host material created by doping a small amount of chemical species, in this case doping samarium in PMN-PT ceramics, as a way to modify the thermodynamic energy landscape of the material, which in turn increases the dielectric properties — the ability of a material to respond to an electrostatic field — and the piezoelectric effect.
“This material is a good choice to use in transducers, such as those used in medical ultrasound,” said lead author Fei Li, a research associate at Penn State. “We already have devices made from our material by a group at the University of Southern California.”
That device, called a needle transducer, uses a submillimeter piezoelectric element of the Penn State material, fitted into a standard needle or catheter, in order to perform minimally invasive procedures, to image inside the body or to guide precision surgery inside the body. The device has better performance than existing devices with the same dimensions, Li said.
The researchers have a provisional patent on this work.
Source: Penn State Materials Research Institute

Fizicienii descoperă noi materiale electronice cuantice(Physicists discover new quantum electronic material)

raportează că au pentru prima dată a produs un metal Kagome – un cristal de conductoare electric, a făcut din straturi de atomi de fier și staniu, cu fiecare strat atomic aranjat în modelul repetat al unei laturi kagome.

Posted: Mar 20, 2018

Physicists discover new quantum electronic material

(Nanowerk News) A motif of Japanese basketweaving known as the kagome pattern has preoccupied physicists for decades. Kagome baskets are typically made from strips of bamboo woven into a highly symmetrical pattern of interlaced, corner-sharing triangles.
If a metal or other conductive material could be made to resemble such a kagome pattern at the atomic scale, with individual atoms arranged in similar triangular patterns, it should in theory exhibit exotic electronic properties.
In a paper published in Nature („Massive Dirac fermions in a ferromagnetic kagome metal”), physicists from MIT, Harvard University, and Lawrence Berkeley National Laboratory report that they have for the first time produced a kagome metal — an electrically conducting crystal, made from layers of iron and tin atoms, with each atomic layer arranged in the repeating pattern of a kagome lattice.
An illustration depicting a kagome metal
An illustration depicting a kagome metal — an electrically conducting crystal, made from layers of iron and tin atoms, with each atomic layer arranged in the repeating pattern of a kagome lattice. (Images by Felice Frankel; Illustration overlays by Chelsea Turner)
When they flowed a current across the kagome layers within the crystal, the researchers observed that the triangular arrangement of atoms induced strange, quantum-like behaviors in the passing current. Instead of flowing straight through the lattice, electrons instead veered, or bent back within the lattice.
This behavior is a three-dimensional cousin of the so-called Quantum Hall effect, in which electrons flowing through a two-dimensional material will exhibit a “chiral, topological state,” in which they bend into tight, circular paths and flow along edges without losing energy.
“By constructing the kagome network of iron, which is inherently magnetic, this exotic behavior persists to room temperature and higher,” says Joseph Checkelsky, assistant professor of physics at MIT. “The charges in the crystal feel not only the magnetic fields from these atoms, but also a purely quantum-mechanical magnetic force from the lattice. This could lead to perfect conduction, akin to superconductivity, in future generations of materials.”
To explore these findings, the team measured the energy spectrum within the crystal, using a modern version of an effect first discovered by Heinrich Hertz and explained by Einstein, known as the photoelectric effect.
“Fundamentally, the electrons are first ejected from the material’s surface and are then detected as a function of takeoff angle and kinetic energy,” says Riccardo Comin, an assistant professor of physics at MIT. “The resulting images are a very direct snapshot of the electronic levels occupied by electrons, and in this case they revealed the creation of nearly massless ‘Dirac’ particles, an electrically charged version of photons, the quanta of light.”
The spectra revealed that electrons flow through the crystal in a way that suggests the originally massless electrons gained a relativistic mass, similar to particles known as massive Dirac fermions. Theoretically, this is explained by the presence of the lattice’s constituent iron and tin atoms. The former are magnetic and give rise to a “handedness,” or chirality. The latter possess a heavier nuclear charge, producing a large local electric field. As an external current flows by, it senses the tin’s field not as an electric field but as a magnetic one, and bends away.
The research team was led by Checkelsky and Comin, as well as graduate students Linda Ye and Min Gu Kang in collaboration with Liang Fu, the Biedenharn Associate Professor of Physics, and postdoc Junwei Liu. The team also includes Christina Wicker ’17, research scientist Takehito Suzuki of MIT, Felix von Cube and David Bell of Harvard, and Chris Jozwiak, Aaron Bostwick, and Eli Rotenberg of Lawrence Berkeley National Laboratory.

“No alchemy required”
Physicists have theorized for decades that electronic materials could support exotic Quantum Hall behavior with their inherent magnetic character and lattice geometry. It wasn’t until several years ago that researchers made progress in realizing such materials.
“The community realized, why not make the system out of something magnetic, and then the system’s inherent magnetism could perhaps drive this behavior,” says Checkelsky, who at the time was working as a researcher at the University of Tokyo.
This eliminated the need for laboratory produced fields, typically 1 million times as strong as the Earth’s magnetic field, needed to observe this behavior.
“Several research groups were able to induce a Quantum Hall effect this way, but still at ultracold temperatures a few degrees above absolute zero — the result of shoehorning magnetism into a material where it did not naturally occur,” Checkelsky says.
At MIT, Checkelsky has instead looked for ways to drive this behavior with “instrinsic magnetism.” A key insight, motivated by the doctoral work of Evelyn Tang PhD ’15 and Professor Xiao-Gang Wen, was to seek this behavior in the kagome lattice. To do so, first author Ye ground together iron and tin, then heated the resulting powder in a furnace, producing crystals at about 750 degrees Celsius — the temperature at which iron and tin atoms prefer to arrange in a kagome-like pattern. She then submerged the crystals in an ice bath to enable the lattice patterns to remain stable at room temperature.
“The kagome pattern has big empty spaces that might be easy to weave by hand, but are often unstable in crystalline solids which prefer the best packing of atoms,” Ye says. “The trick here was to fill these voids with a second type of atom in a structure that was at least stable at high temperatures. Realizing these quantum materials doesn’t need alchemy, but instead materials science and patience.”

Bending and skipping toward zero-energy loss
Once the researchers grew several samples of crystals, each about a millimeter wide, they handed the samples off to collaborators at Harvard, who imaged the individual atomic layers within each crystal using transmission electron microscopy. The resulting images revealed that the arrangement of iron and tin atoms within each layer resembled the triangular patterns of the kagome lattice. Specifically, iron atoms were positioned at the corners of each triangle, while a single tin atom sat within the larger hexagonal space created between the interlacing triangles.
Ye then ran an electric current through the crystalline layers and monitored their flow via electrical voltages they produced. She found that the charges deflected in a manner that seemed two-dimensional, despite the three-dimensional nature of the crystals. The definitive proof came from the photoelectron experiments conducted by co-first author Kang who, in concert with the LBNL team, was able to show that the electronic spectra corresponded to effectively two-dimensional electrons.
“As we looked closely at the electronic bands, we noticed something unusual,” Kang adds. “The electrons in this magnetic material behaved as massive Dirac particles, something that had been predicted long ago but never been seen before in these systems.”
“The unique ability of this material to intertwine magnetism and topology suggests that they may well engender other emergent phenomena,” Comin says. “Our next goal is to detect and manipulate the edge states which are the very consequence of the topological nature of these newly discovered quantum electronic phases.”
Looking further, the team is now investigating ways to stabilize other more highly two-dimensional kagome lattice structures. Such materials, if they can be synthesized, could be used to explore not only devices with zero energy loss, such as dissipationless power lines, but also applications toward quantum computing.
“For new directions in quantum information science there is a growing interest in novel quantum circuits with pathways that are dissipationless and chiral,” Checkelsky says. “These kagome metals offer a new materials design pathway to realizing such new platforms for quantum circuitry.”
Source: By Jennifer Chu, MIT

Cercetătorii îmbunătățesc procesul de fabricare a nanostructurilor pentru dispozitivele electronice(Researchers improve fabrication process of nanostructures for electronic devices)

Indium-galiu-fosfid este unul din mai multe materiale testate pentru a completa siliciul ca mijloc de imbunatatire a capacitatii curente de prelucrare a semiconductoarelor.
„Acesta este un material foarte bine cunoscut și are aplicații în industria electronică și în celulele solare”, a spus el. „Nu inventăm din nou roata; noi stabilim noi protocoale pentru tratarea materialelor existente, care sunt mai rentabile și un proces mai durabil „.
Dispozitivele semiconductoare sunt create pe plachete printr-un proces în mai multe etape pentru acoperirea, îndepărtarea sau modelarea materialelor conductive. Procesele tradiționale sunt etchul umed, unde o probă cu aspecte blocate este imersată într-o baie acidă pentru îndepărtarea substanțelor și o gravare cu ioni reactivi, unde ionii bombardează suprafețele expuse pe placă pentru a-și schimba proprietățile chimice și a elimina materialele din aceste zone expuse. Ambele au fost utilizate pentru a dezvolta modelele complexe electronice pe circuite și pentru a folosi siliciul ca fundație pentru acest tip de modelare. Îmbunătățirea metodelor de modelare de către I-MacEtch ar putea însemna reducerea complexității fabricării diferitelor dispozitive fotonice și electronice.

Posted: Mar 20, 2018

Researchers improve fabrication process of nanostructures for electronic devices

(Nanowerk News) Researchers at RIT have found a more efficient fabricating process to produce semiconductors used in today’s electronic devices. They also confirmed that materials other than silicon can be used successfully in the development process that could increase performance of electronic devices. This fabrication process—the I-MacEtch, or inverse metal-assisted chemical etching method—can help meet the growing demand for more powerful and reliable nano-technologies needed for solar cells, smartphones, telecommunications grids and new applications in photonics and quantum computing.
“What is novel about our work is that for the first time we are looking at applying I-MacEtch processing to indium-gallium-phosphide materials. I-MacEtch is an alternative to two conventional approaches and is a technique that has been used in the field—but the materials that have been explored are fairly limited,” said Parsian Mohseni, assistant professor of microsystems engineering in RIT’s Kate Gleason College of Engineering. He is also director of the EINS Laboratory at the university.
Au-assisted and inverse-progression MacEtch (I-MacEtch) of the heteroepitaxial In0.49Ga0.51P/GaAs material system
Au-assisted and inverse-progression MacEtch (I-MacEtch) of the heteroepitaxial In0.49Ga0.51P/GaAs material system. (© ACS)
Demands for improved computer processing power have led researchers to explore both new processes and other materials beyond silicon to produce electronic components, Mohseni explained. The I-MacEtch process combines the benefits of two traditional methods—wet etching and reactive ion etching, or REI. Indium-gallium-phosphide is one of several materials being tested to complement silicon as a means to improve current capacity of semiconductor processing.
“This is a very well-known material and has applications in the electronics and solar cell industries,” he said. “We are not re-inventing the wheel; we are establishing new protocols for treating the existing material that is more cost effective, and a more sustainable process.”
Semiconductor devices are created on wafers through a multi-step process to coat, remove or pattern conductive materials. Traditional processes are wet etch, where a sample with blocked aspects is immersed in an acid bath to remove substances, and reactive ion etching, where ions bombard exposed surfaces on the wafer to change its chemical properties and remove materials in those exposed regions. Both have been used to develop the intricate electronic patterns on circuits and use silicon as a foundation for this type of patterning. Improving patterning methods by I-MacEtch could mean reducing fabrication complexity of various photonic and electronic devices.
Researchers and semiconductor fabrication scientists have been using MacEtch extensively for processing silicon. At the same time, assessments of other materials in the III-V range of individual elements that may be conducive to this same type of fabrication with similar advantages are underway. In his research, Mohseni is also looking at different alloys of those III-V materials, namely the ternary alloys such as indium-gallium-phosphide (InGaP).
The research detailed in the upcoming issue of the American Chemical Society’s Applied Materials and Interfaces journal („Fabrication of Suspended III-V Nanofoils by Inverse Metal-Assisted Chemical Etching of In0.49Ga0.51P/GaAs Heteroepitaxial Films”) highlights how the nanofabrication methodology was applied to InGaP and how it can impact the processing of device applications and generation of high aspect ratio and nano-scale semiconductor features, said Thomas Wilhelm, a microsystems engineering doctoral student and first-author of the paper. The novel processing method can be significant in the development of ordered arrays of high aspect ratio structures such as nanowires.
For solar cells, the goal is to minimize the cost-to-power-produced ratio, and if it is possible to lower the cost of making the cell, and increasing the efficiency of it, this improves the device overall. Exploring new methods of fabricating the existing, relevant materials in a way that allows for faster, less expensive and more controlled processing by combining the benefits of wet etching and RIE has been the focus of Mohseni’s work. The improved process means avoiding expensive, bulky, hazardous processing methods.
“We are using a simple benchtop set up and we end up with very similar structures; in fact, one can argue that they are higher in quality than the structures that we can generate with RIE for a fraction of the cost and with less time, less steps throughout, without the higher temperature conditions or expensive instrumentation,” he said.
Source: By Michelle Cometa, Rochester Institute of Technology

Ce plante ne pot învăța despre curățarea scurgerilor de petrol, microfluidice(What plants can teach us about oil spill clean-up, microfluidics)

ia un indiciu din structura frunzei pentru fabricarea materialului care poate separa petrolul și apa, ceea ce ar putea duce la o mai mare siguranță și mai multă siguranță metode eficiente de curățare a scurgerilor de petrol.
În plus, materialul este capabil să „manipuleze microdroplet”, sau transferul de volume miniaturate de lichid. Microfluidica pe bază de picături este o unealtă utilizată în diverse aplicații cum ar fi culturile celulare, sinteza chimică și secvențializarea ADN-ului.Echipa a tipărit 3-D un prototip, citând o cerere în creștere de materiale care pot separa amestecurile de ulei și apă eficient în corpuri vaste de apă. În cele din urmă, ei speră că tehnologia poate fi aplicată pentru fabricarea de materiale la scară largă pentru a se adapta scurgeri masive de petrol în ocean. Metodele actuale necesită o energie extraordinară sub forma unui câmp electric sau a unei presiuni aplicate mecanic.

Posted: Mar 20, 2018

What plants can teach us about oil spill clean-up, microfluidics

(Nanowerk News) For years, scientists have been inspired by nature to innovate solutions to tricky problems, even oil spills – manmade disasters with devastating environmental and economic consequences. A new USC study (Advanced Materials, „3D-Printed Biomimetic Super-Hydrophobic Structure for Microdroplet Manipulation and Oil/Water Separation”) takes a cue from leaf structure to fabricate material that can separate oil and water, which could lead to safer and more efficient oil spill clean-up methods.
In addition, the material is capable of „microdroplet manipulation,” or the transfer of miniature volumes of liquid. Droplet-based microfluidics is a tool used in various applications like cell cultures, chemical synthesis and DNA sequencing.
3-D Printed Prototype of Egg-Beater Structure
3-D Printed Prototype of Egg-Beater Structure. (Image: Yang Yang, USC)
Using 3-D printing, Associate Professor Yong Chen and his research team at the Daniel J. Epstein School of Industrial and Systems Engineering at the USC Viterbi School of Engineering have successfully mimicked a biological phenomenon in plant leaves called „Salvinia effect.” Their study focuses on a floating fern native to South America called Salvinia molesta. The unique leaves are super-hydrophobic, meaning „water-fearing” and retain a surrounding air pocket when submerged in water due to the presence of water-resistant hairs.
„I think the reason the plant’s surface is super-hydrophobic is because it lives on the water and requires air to survive,” Yang Yang, a postdoctoral researcher on Chen’s team, said. „If it weren’t for the long-term evolution of this plant, the plant could be submerged in water and would die.”

Water-repellent structure
On a microscopic level, the leaf hairs align in a structure resembling an egg-beater, or cooking whisk. Chen explains that Salvinia’s leaf surface is comprised of this so-called „egg-beater” structure that is super-hydrophobic.
Using a method called immersed surface accumulation 3-D printing (ISA-3D printing), the research team successfully created the egg-beater microstructure in samples made from plastic and carbon nanotubes. Chen explains that the method allowed the team to demonstrate the fabrication of a material with both super-hydrophobic and olephilic (oil-absorbing) properties that, when combined, generate capillary forces capable of highly efficient oil and water separation.
„We tried to create one functional surface texture that would be able to separate oil from water,” Chen said. „Basically, we modified the surface of the materials by using a 3-D printing approach that helped us achieve some interesting surface properties.”
The team has 3-D printed a prototype, citing a growing demand for materials that can separate oil and water mixtures efficiently in vast bodies of water. Eventually, they hope the technology can be applied to manufacture materials in large scale to accommodate massive oil spills in the ocean. Current methods require tremendous energy in the form of an electric field or mechanically-applied pressure.

Microfluidics application
„Salvinia effect” also has potential for liquid-handling technology that executes „microdroplet manipulation” –a breakthrough where the adhesion of liquid to a robotic arm can be tuned accordingly and result in non-loss transfer for very tiny amounts of liquid. The technique can be applied in myriad ways, some of which include droplet-based microreactors (devices used in chemical synthesis), nanoparticle synthesis, tissue engineering, drug discovery and drug delivery monitoring.
Xiangjia Li, a PhD student on Chen’s team and co-first author of the study, says one example of high-performance microdroplet manipulation could lead to more efficient blood analyses for patients. A robotic gripper could move to different stations and dispense microdroplets of blood that are then evenly mixed with different chemicals for various tests. In addition, the tests could be designed to control the ratio of chemical to droplet and result in significant conservation for source materials and chemical reagents.
„You can have a robotic arm with a gripper made to mimic ‘Salvinia effect,'” Li said. „No matter which way you move the arm, the gripping force is so large that a droplet will stay attached.”
Source: University of Southern California

Grafen din înaltă calitate din nichel(High quality graphene from nickel)

Grafenul este un material bidimensional, foarte subțire, compus dintr-un singur strat de atomi de carbon, dar și flexibil, cum ar fi plasticul și cu o rezistență mecanică de o sută de ori mai mare decât oțelul. Acesta este motivul pentru care este considerat practic perfect pentru utilizări multiple în domenii industriale și tehnologice; cu toate acestea, este dificil să se producă, ceea ce face ca utilizarea sa să fie extrem de costisitoare.

Posted: Mar 19, 2018

High quality graphene from nickel

(Nanowerk News) A study published in Science („Real-time imaging of adatom-promoted graphene growth on nickel”) unveils the catalytic action of nickel in the growth of graphene sheets. The research, carried out by Iom-Cnr and the University of Trieste, provides new strategies to improve the industrial production of this material characterized by exceptional properties
Graphene is a two-dimensional material, very thin, composed of a single layer of carbon atoms, but also flexible like plastic and with a mechanical resistance a hundred times higher than steel. This is why it is considered practically perfect for multiple uses in industrial and technological fields; however, it is difficult to produce, making its use extremely expensive.
„We know that individual atoms are always present on metal surfaces, where they can freely move around and participate in many of the processes that take place there”, explains Cristina Africh, of Iom-Cnr. „In our study we have shown that, on a nickel surface, the mobile metal atoms act as catalysts, facilitating the formation of graphene”.
The scientific team was able to record this process in real time, revealing the behavior of individual surface atoms, by means of a high-speed scanning module developed in the recent years in collaboration with Elettra-Sincrotrone Trieste and recently improved thanks to European funding.
„With a scanning tunneling microscope”, continues Laerte Patera, who worked on this project at Iom-Cnr for his PhD thesis in nanotechnology at the University of Trieste, „we filmed what happens at the edge of the graphene sheet during its growth, at a temperature of about 450 degrees Celsius, collecting up to 60 images per second, a frame rate much higher than those used in cinematography or in television and perceived by the human eye”.
„From the videos it is clear that the growth process takes place line by line, like a knitting machine weaving a thread to form a piece of cloth: at the microscopic level, the individual nickel atoms perform the same function as the machine needle, adding new stitches to the edge of the fabric in an ordered sequence”, explains Giovanni Comelli, from the University of Trieste. „Numerical simulations, conducted at our University under the guidance of Maria Peressi and performed in collaboration with the Universidad Nacional de Córdoba (Argentina), mostly based on quantum mechanics, clarify all details of the experimental results and clearly explain the role played by nickel adatoms which, by temporarily attaching themselves at the graphene edges, allow the inclusion of new carbon atoms.”
„In addition to its relevant scientific value, this result is of considerable interest for applications, since one of the most widely used methods currently employed for industrial production of graphene makes use of a nickel substrate to grow graphene layers characterized by few defects at a reduced production cost”, concludes Africh. „Understanding the details of the growth mechanism, so far unknown, is therefore fundamental to define a strategy for the development of new and more efficient graphene production processes at the industrial level”.
Source: Consiglio Nazionale delle Ricerche

Pansamentele din nanofibre vindecă rănile, promovează regenerarea(Nanofiber dressings heal wounds, promote regeneration)

au dezvoltat pansamente noi rana, care accelereaza dramatic vindecarea si imbunatatirea regenerarii tesutului. Cele două tipuri diferite de pansamente nanofibre, descrise în lucrări separate, utilizează proteine ​​care apar în plante și animale pentru a promova vindecarea și regenerarea țesuturilor.
„Sistemul nostru de fabricație a fibrelor a fost dezvoltat special pentru a dezvolta terapeutica pentru rănile de război”Aceste descoperiri arata marea promisiune a nanofibrelor pe baza de soia pentru vindecarea ranilor,Ambele tipuri de îmbrăcăminte, potrivit cercetătorilor, au avantaje în spațiul de vindecare a rănilor. Nanofibrele pe bază de soia – constând din acetat de celuloză și hidrolizat de proteine ​​din soia – sunt ieftine, făcându-le o opțiune bună pentru utilizarea pe scară largă, cum ar fi arsurile. Pansamentele de fibronectină, pe de altă parte, ar putea fi folosite pentru răni mai mici pe față și pe mâini, unde prevenirea cicatrizării este importantă.

Posted: Mar 19, 2018

Nanofiber dressings heal wounds, promote regeneration

(Nanowerk News) Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have developed new wound dressings that dramatically accelerate healing and improve tissue regeneration. The two different types of nanofiber dressings, described in separate papers, use naturally-occurring proteins in plants and animals to promote healing and regrow tissue.
„Our fiber manufacturing system was developed specifically for the purpose of developing therapeutics for the wounds of war,” said Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at SEAS and senior author of the research. „As a soldier in Afghanistan, I witnessed horrible wounds and, at times, the healing process for those wounds was a horror unto itself. This research is a years-long effort by many people on my team to help with these problems.”
Parker is also a Core Faculty Member of the Wyss Institute.
The most recent paper, published in Biomaterials („Production-scale fibronectin nanofibers promote wound closure and tissue repair in a dermal mouse model”), describes a wound dressing inspired by fetal tissue.
Hair Follicle Regeneration
This is a tissue section 14 days post-wounding reveals the presence of hair follicles regenerating at the center of the wound. Re-growing hair follicles is one of the biggest challenges in the field of wound healing. (Image: Disease Biophysics Group/Harvard University)
In the late 1970s, when scientists first started studying the wound healing process early in development, they discovered something unexpected: wounds incurred before the third trimester left no scars. This opened a range of possibilities for regenerative medicine. But for decades, researchers have struggled to replicate those unique properties of fetal skin.
Unlike adult skin, fetal skin has high levels of a protein called fibronectin, which assembles into the extracellular matrix and promotes cell binding and adhesion. Fibronectin has two structures: globular, which is found in blood, and fibrous, which is found in tissue. Even though fibrous fibronectin holds the most promise for wound healing, previous research focused on the globular structure, in part because manufacturing fibrous fibronectin was a major engineering challenge.
But Parker and his team are pioneers in the field of nanofiber engineering.
The researchers made fibrous fibronectin using a fiber manufacturing platform called Rotary Jet-Spinning (RJS), developed by Parker’s Disease Biophysics Group. RJS works likes a cotton candy machine – a liquid polymer solution, in this case globular fibronectin dissolved in a solvent, is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. As the solution leaves the reservoir, the solvent evaporates and the polymers solidify. The centrifugal force unfolds the globular protein into small, thin fibers. These fibers – less than one micrometer in diameter – can be collected to form a large-scale wound dressing or bandage.
„The dressing integrates into the wound and acts like an instructive scaffold, recruiting different stem cells that are relevant for regeneration and assisting in the healing process before being absorbed into the body,” said Christophe Chantre, a graduate student in the Disease Biophysics Group and first author of the paper.
In in vivo testing, the researchers found that wounds treated with the fibronectin dressing showed 84 percent tissue restoration within 20 days, compared to 55.6 percent restoration in wounds treated with a standard dressing.
The researchers also demonstrated that wounds treated with the fibronectin dressing have close to normal epidermal thickness and dermal architecture, and even regrew hair follicles – often considered one of the biggest challenges in the field of wound healing.
„This is an important step forward,” said Chantre. „Most work done on skin regeneration to date involves complex treatments combining scaffolds, cells and even growth factors. Here we were able to demonstrate tissue repair and hair follicle regeneration using an entirely material approach. This has clear advantages for clinical translation.”
In another paper published in Advanced Healthcare Materials („Soy Protein/Cellulose Nanofiber Scaffolds Mimicking Skin Extracellular Matrix for Enhanced Wound Healing”), the Disease Biophysics Group demonstrated a soy-based nanofiber that also enhances and promotes wound healing.
Soy protein contains both estrogen-like molecules – which have been shown to accelerate wound healing – and bioactive molecules similar to those that build and support human cells.
„Both the soy and fibronectin fiber technologies owe their success to keen observations in reproductive medicine,” said Parker. „During a woman’s cycle, when her estrogen levels go high, a cut will heal faster. If you do a surgery on a baby still in the womb, they have scar-less wound healing. Both of these new technologies are rooted in the most fascinating of all the topics in human biology – how we reproduce.”
In a similar way to fibronectin fibers, the research team used RJS to spin ultra-thin soy fibers into wound dressings. In experiments, the soy and cellulose-based dressing demonstrated a 72-percent increase in healing over wounds with no dressing and a 21-percent increase in healing over wounds dressed without soy protein.
„These findings show the great promise of soy-based nanofibers for wound healing,” said Seungkuk Ahn, a graduate student in the Disease Biophysics Group and first author of the paper. „These one-step, cost-effective scaffolds could be the next generation of regenerative dressings and push the envelope of nanofiber technology and the wound care market.”
Both kinds of dressing, according to researchers, have advantages in the wound-healing space. The soy-based nanofibers – consisting of cellulose acetate and soy protein hydrolysate – are inexpensive, making them a good option for large-scale usage, such as on burns. The fibronectin dressings, on the other hand, could be used for smaller wounds on the face and hands, where the prevention of scarring is important.
Source: Harvard John A. Paulson School of Engineering and Applied Sciences

Studiul la scară atomică arată noi perspective asupra modului în care funcționează celulele solare perovskite(Atomic scale study reveals new insights into how hybrid perovskite solar cells work)

au acumulat noi perspective asupra unui mister fundamental despre perovskite hibride, materiale cu costuri reduse care ar putea imbunatati sau chiar sa inlocuiasca celulele solare conventionale din siliciu. Constatarile noastre ar putea sa ne permita sa intelegem de ce compozitia de plumb functioneaza atat de bine in timp ce alte materiale nu, si de a investiga degradarea acestor dispozitive, uitandu-se direct la structura atomica si modul in care se schimba.

Posted: Mar 19, 2018

Atomic scale study reveals new insights into how hybrid perovskite solar cells work

(Nanowerk News) Scientists have gained new insights into a fundamental mystery about hybrid perovskites, low-cost materials that could enhance or even replace conventional solar cells made of silicon.
Under a microscope, a slice of perovskite looks like an abstract mosaic of random grains of crystal. The mystery is how this patchwork of tiny, imperfect grains can transform sunlight into electricity as efficiently as a single crystal of pure silicon.
A recent study by scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory offers new clues. Writing in Advanced Materials („Terahertz Emission from Hybrid Perovskites Driven by Ultrafast Charge Separation and Strong Electron–Phonon Coupling”), the scientists provide a new understanding of how electric charges separate in perovskites a few billionths of a second following the absorption of light, the crucial first step in generating an electric current.
his illustration depicts what happens inside a hybrid perovskite material in the first few trillionths of a second after it's hit with simulated sunlight
This illustration depicts what happens inside a hybrid perovskite material in the first few trillionths of a second after it’s hit with simulated sunlight (upper left). The blue and green spheres are atoms, arranged in double pyramids as shown at left. When light hits, electrons start to separate from positively charged “holes,” the first step in creating an electrical current (yellow streaks). Meanwhile, atoms begin to vibrate within the perovskite’s lattice-like structure. Scientists detected these processes by analyzing the terahertz radiation (red streaks) the processes released. (Image: Greg Stewart/SLAC National Accelerator Laboratory)
The study is the first to probe the inner workings of hybrid perovskites at the atomic scale using laser pulses that match the intensity of solar radiation, and thus mimic natural sunlight. The authors say their discovery could lead to improvements in the performance of perovskite solar cells and a new way to probe their functionality.

Perovskites and Silicon
Most solar cells today are made of purified silicon manufactured at temperatures above 3,000 degrees Fahrenheit (1,600 degrees Celsius). These rigid silicon panels can last for decades in all kinds of weather conditions.
Perovskite solar cells, although far less durable, are thinner and more flexible than silicon cells and can be produced near room temperature from a hybrid mixture of cheap organic and inorganic materials, like iodine, lead and methylammonium.
Researchers, including Stanford co-author Michael McGehee, have shown that perovskite solar cells are as efficient at converting light to electricity as commercially available silicon cells and can even outperform them. This combination of efficiency, flexibility and easy synthesis has fueled a worldwide race to develop commercial-grade perovskites that can withstand long-term exposure to heat and precipitation.
“Perovskites are very promising materials for photovoltaics,” said lead author Burak Guzelturk, a postdoctoral scholar at Stanford and SLAC. “But people wonder how they can achieve such high efficiencies.”

Electrons and Holes
All solar cells operate on the same principle. Photons of sunlight absorbed by the crystalline material kick negatively charged electrons into an excited state. The freed electrons leave behind positively charged spaces or “holes” that separate from one another. This separation gives rise to an electric current.
Pure silicon, with its highly ordered atomic structure, provides a direct path for electrons and holes to travel through the solar cell. But with perovskites, the road is far from smooth.
“Perovskites are typically filled with defects,” said co-author Aaron Lindenberg, an associate professor at SLAC and Stanford and investigator with the Stanford Institute of Materials and Energy Sciences (SIMES). “They’re not even close to being perfect crystals, yet somehow the electric currents don’t see the defects.”

Terahertz Emission
For the study, the research team used laser pulses to simulate waves of sunlight from both ends of the visible light spectrum – high-energy violet light and low-energy infrared light. The results were measured at the picosecond timescale. One picosecond is one trillionth of a second.
“In the first picoseconds after sunlight hits the perovskite, the electrons and holes in the crystalline lattice start to split,” Lindenberg explained. “The separation was uncovered by measuring the emission of high-frequency terahertz light pulses oscillating a trillion times per second from the perovskite thin film. This is the first time anyone has observed terahertz emission from hybrid perovskites.”
The terahertz emission also revealed that electrons and holes closely interact with lattice vibrations in the crystalline material. This interaction, which occurs on a femtosecond timescale, could help explain how electric currents navigate through the patchwork of crystal grains in hybrid perovskites.
„As the electric charges separate, we observe a sharp spike in the terahertz emission, matching a vibrational mode of the material,” Guzelturk said. “That gives us clear evidence that the electrons and holes are strongly coupling with the atomic vibrations in the material.”
This finding raises the possibility that coupling to the lattice vibration could protect the electrons and holes from charged defects in the perovskite, shielding the electric current as it travels through the solar cell. Similar scenarios have been proposed by other research teams.
“This is one of the first observations of how the local atomic structure of a hybrid perovskite material responds in the first trillionths of a second after absorbing sunlight,” Lindenberg said. “Our technique could open up a new way of probing a solar cell right when the photon is absorbed, which is really important if you want to understand and build better materials. The conventional way is to put electrodes on the device and measure the current, but that essentially blurs out all of the microscopic processes that are key. Our all-optical, electrode-less approach with femtosecond time resolution avoids that problem.”

Hot Electrons
The researchers also found that terahertz light fields are much stronger when perovskite is hit with high-energy light waves.
“We found that radiated terahertz light is orders of magnitudes more intense when you excite the electrons with violet light versus low-energy infrared light,” Lindenberg said. “That was an unexpected result.”
This discovery could provide new insights on high-energy “hot” electrons, Guzelturk said.
“Violet light imparts electrons with excess kinetic energy, creating hot electrons that move much faster than other electrons,” he said. “However, these hot electrons lose their excess energy very rapidly.”
Harnessing the energy from hot electrons could lead to a new generation of high-efficiency solar cells, added Lindenberg.
“One of the grand challenges is finding a way to capture the excess energy from a hot electron before it relaxes,” he said. “The idea is that if you could extract the current associated with hot electrons before the energy dissipates, you could increase the efficiency of the solar cell. People have argued that it’s possible to create hot electrons in perovskites that live much longer than they do in silicon. That’s part of the excitement around perovskites.”
The study revealed that in hybrid perovskites, hot electrons separate from holes faster and more efficiently than electrons excited by infrared light.
“For the first time we can measure how fast this separation occurs,” Lindenberg said. “This will provide important new information on how to design solar cells that use hot electrons.”

Toxicity and Stability
The ability to measure terahertz emissions could also lead to new research on non-toxic alternatives to conventional lead-based perovskites, said Guzelturk.
“Most of the alternative materials being considered are not as efficient at generating electricity as lead,” he said. “Our findings might allow us to understand why lead composition works so well while other materials don’t, and to investigate the degradation of these devices by looking directly at the atomic structure and how it changes.”
Source: SLAC National Accelerator Laboratory