Lună: ianuarie 2018

Material perlat pentru elemente de încălzire flexibile(Pearly material for bendable heating elements)

Oamenii de stiinta de astazi raporteaza in ACS Applied Nano Materials ( „Nacre Mimetic cu Nanowire de argint incorporat pentru incalzire rezistiva” ) un material hibrid compus din imitatie de perle combinata cu nanofire de argint care functioneaza ca un incalzitor, cu beneficiul suplimentar de flexibilitate ridicata, sugerand un potential rol în dispozitive portabile.Nacre, altfel cunoscut sub numele de mama de perle, formează învelișul opalescent exterior al unei perle și învelișul interior al cochililor de moluscă. Oamenii de știință au fost mult timp interesați de acest material ușor, dar puternic pentru o gamă largă de aplicații, fabricând substanțe care imită pergul pentru utilizare ca agenți de întârziere a incendiilor, bariere de gaz și conductori.Materialul compozit a prezentat proprietăți excelente de încălzire, generând căldură, deoarece curentul electric a fost trecut prin nanofirele de argint, chiar și atunci când a fost îndoit în mod repetat sau când a fost laminat într-un tub. Într-un experiment de dovadă a conceptului, cercetătorii au plasat pe încălzitor un plasture cu hidrogel încărcat cu antibiotice sensibil la căldură. Întoarcerea la temperatură a declanșat o modificare a fazei în plasture, eliberând antibioticele.

Posted: Jan 24, 2018

Pearly material for bendable heating elements

(Nanowerk News) The iridescent shimmer of a string of pearls may one day be more than pretty adornment. Scientists now report in ACS Applied Nano Materials („Nacre Mimetic with Embedded Silver Nanowire for Resistive Heating”) a hybrid material consisting of imitation pearl combined with silver nanowires that works as a heater, with the added benefit of high flexibility, suggesting a potential role in wearable devices.
Nacre, otherwise known as mother of pearl, makes up the opalescent exterior coating of a pearl and the inner coating of mollusk shells. Scientists have long been interested in this lightweight, yet strong material for a range of applications, manufacturing substances that imitate nacre for use as fire retardants, gas barriers and conductors.
Flexible conductors made from silver nanowires and a flexible plastic substrate called polyethylene terephthalate (PET) are being developed in laboratories, but researchers are running into problems with adhesion between PET and the silver nanowires. So, Hongwei Duan and colleagues wanted to explore a nacre mimetic as the substrate for silver nanowires to develop a flexible resistive heater.
The researchers prepared the nacre mimetic from a synthetic nanoclay coated with a polyvinyl alcohol polymer that self-assembled upon water removal, generating a flexible transparent sheet. Then, they transferred silver nanowires from a filter membrane to the nacre mimetic sheet by hot pressing the pearly substrate against the membrane. The silver nanowires adhered to the new material better than to traditional flexible plastic substrates, resisting removal with scotch tape, a standard test of adhesion.
The composite material showed excellent heating properties, producing heat as electric current was passed through the silver nanowires, even when bent repeatedly or when rolled up into a tube. In a proof-of-concept experiment, the researchers placed a heat-sensitive antibiotic-loaded hydrogel patch onto the heater. Turning up the temperature triggered a phase change in the patch, releasing the antibiotics.
Source: American Chemical Society

Filtrele noi ar putea permite producătorilor să efectueze separări chimice foarte selective(New filters could enable manufacturers to perform highly selective chemical separation)

Membranele se bazează pe polimeri care se auto-asamblează, formează nanostructuri și expun funcționalități chimice care le permit să îndeplinească sarcini care nu sunt așteptate de la membrane. Ei elimină nu numai bacteriile, ci și metalele grele, reacționează la stimuli și separă moleculele mici de structura chimică. În ansamblu, obiectivul este de a dezvolta membrane care să contribuie la generarea mai eficientă a apei curate și mai sigure și la separarea substanțelor chimice cu consum redus de energie.

Posted: Jan 23, 2018

New filters could enable manufacturers to perform highly selective chemical separation

(Nanowerk News) A team of chemical and biological engineers has developed highly selective membrane filters that could enable manufacturers to separate and purify chemicals in ways that are currently impossible, allowing them to potentially use less energy and cut carbon emissions, according to findings published in print today in the journal ACS Nano („Selective Transport through Membranes with Charged Nanochannels Formed by Scalable Self-Assembly of Random Copolymer Micelles”).
Tufts University scientists said the sophisticated membranes can separate organic compounds not only by size–as small as a molecule–but also by their electrostatic charge, meaning manufacturers could sort compounds by both size and type. The membranes use a simple, scalable process in which a specialty polymer is dissolved in a solvent and coated onto a porous support. The polymer self-assembles to create approximately 1 nanometer size channels that mimic biological systems, such as ion channels, which control the passage of compounds through cell membranes with great effectiveness.
Membrane structure
Membrane structure; the top layer (pink) shows selective layer morphology containing packed micelles. The spaces between the micelles form membrane nanopores with size of 1-3 nanometer. (Image: Ilin Sadeghi, study co-author and Tufts University Ph.D. candidate)
Corresponding-author Ayse Asatekin, Ph.D., a chemical and biological engineering professor in the Tufts School of Engineering, said the team’s discovery responds to industry-wide calls for the development of more efficient solutions for separating chemicals, which accounts for 10 to 15 percent of global energy use, according to a report in Nature.
„Our study is promising because it is the first demonstration of a new way of making these selective membranes that are so important for chemical manufacturing,” she said. „Designing very selective membranes that can perform these complex separations could really boost energy efficiency and greatly reduce manufacturing waste.”
The newly designed membranes can:
  • Allow neutral compounds to pass through 250 times faster than charged compounds of similar size;
  • When charged and uncharged compounds are mixed, prevent the charged compound from passing through at all–its passage is averted because the neutral compound gets into the channels first and prevents the charge compound from entering; and
  • Provide the ability to separate charged and uncharged compounds in various filtration systems.
Asatekin noted that the charge-based separation is enhanced when the solution contains a mixture of solutes, which indicates that the membrane structure successfully mimics how biological systems such as ion channels operate. This discovery has led the researchers to believe that this approach can be used to address other separations, and bring about selectivities above and beyond what can be attained using conventional membranes.
„This means we could potentially make filters that are capable of separations that cannot be achieved currently. Filters today usually are limited to separating big from small, and we want to be able to separate compounds that are the same size but different,” Asatekin said.
Asatekin noted some potential applications for this project include the purification of antibiotics, amino acids, antioxidants and other small molecule biologic compounds, and the separation of ionic liquids from sugar in biorefinery facilities. However, she said she believes this general approach may potentially be adapted further to different separations with further research.
Asatekin serves as the principal investigator of the Smart Polymers, Membranes, and Separations Laboratory at Tufts. The lab aims to develop the next generation of membranes by designing them from molecules up. The membranes rely on polymers that self-assemble, form nanostructures, and expose chemical functionalities that enable them to perform tasks normally not expected from membranes. They remove not only bacteria but also heavy metals, react to stimuli, and separate small molecules by chemical structure. Overall, the goal is to develop membranes that will help generate clean, safe water more efficiently and separate chemicals with lower energy use.
Source: Tufts University

Oamenii de știință dezvoltă metamateriale cuantice de la qubits gemeni complexe(Scientists develop quantum metamaterial from complex twin qubits)

Ei au reușit să creeze primul metamaterial cuantic al lumii, care poate fi folosit ca element de control în circuitele electrice superconductoare .Metamaterialele sunt substanțe ale căror proprietăți sunt determinate nu atât de atomii din care sunt compuși, cât și de structura structurală a atomilor. Fiecare structură are sute de nanometri și are un set propriu de proprietăți care dispar atunci când oamenii de știință încearcă să separe materialul în componentele sale. De aceea, o astfel de structură se numește meta-atom (nu trebuie confundată cu atomii obișnuiți ai Mendeleev’s Periodic Table). Orice substanță constând din meta-atomi se numește meta-material.

Posted: Jan 23, 2018

Scientists develop quantum metamaterial from complex twin qubits

(Nanowerk News) An international team consisting of Russian and German scientists has made a breakthrough in the creation of seemingly impossible materials. They have managed to create the world`s first quantum metamaterial which can be used as a control element in superconducting electrical circuits (Nature Communications, „Magnetically induced transparency of a quantum metamaterial composed of twin flux qubits”).
A Quantum Metamaterial Made of Twin Flux Qubits
Superconducting quantum metamaterial consisting of an array of 15 twin qubits embedded in a coplanar wave guide. An SEM image of twin flux qubits (above) and a whole structure (below) are shown. Each qubit consists of two superconducting loops sharing one common central Josephson junction (α-junction) and four identical Josephson junctions located on the outer parts of the loops. The α-junction allows the magnetic flux to tunnel between the loops. The inset is a schematic of a single meta-atom–the twin flux qubit; the phases on nodes are shown. (Image: NUST MISIS)
Metamaterials are substances whose properties are determined not so much by the atoms they consist of, but by the atoms’ structural arrangement. Each structure is hundreds of nanometers, and has its own set of properties that disappear when scientists try to separate the material into its components. That is why such a structure is called a meta-atom (not to be confused with the common atoms of Mendeleev`s Periodic Table). Any substance consisting of meta-atoms is called a meta-material.
Until recently, another difference between atoms and meta-atoms was that the properties of conventional atoms were described by quantum mechanics equations, while meta-atoms were described by classical physics equations. However, the creation of qubits led to the emergence of a potential opportunity to construct metamaterials consisting of meta-atoms whose state could be described quantum-mechanically. However, this research required the creation of unusual qubits.
„An international team of scientists from NUST MISIS, Karlsruhe Institute of Technology (Germany), and IPHT Jena (Germany), led by Professor Alexey Ustinov, head of the NUST MISIS Laboratory of Superconducting Metamaterials, has created the world`s first so-called „twin” qubit, as well as a metamaterial on its basis. Thanks to the outstanding properties of the new material, it will be possible to create one of the key elements in superconducting electronic devices”, said Alevtina Chernikova, Rector of NUST MISIS.
Kirill Shulga, a researcher at the NUST MISIS Laboratory of Superconducting Metamaterials and the first author of the project, noted that a conventional qubit consists of a scheme that includes three Josephson junctions. The twin qubit however is composed of five junctions that are symmetric to the Central axis (see diagram).
Magnetic Field Dependence of the Transition Frequencies of the Twin Qubit
The energy of the ground state (a) and the transition energy hf01 of the twin qubit. The minimum point of the (b) plot corresponds to the transition of the central junction phase. (Image: NUST MISIS)
„Twin qubits were supposed to serve as a more complex system than the conventional superconducting qubits. The logic here is quite simple: a more complex (artificially complex) system, with a large number of degrees of freedom, has a higher number of factors that can influence its properties. When changing some external properties of the environment where our metamaterial is located, we can turn these properties on and off by turning the twin qubit from one state with certain properties to another with other properties”, he added.
This became apparent during the experiment, as the whole metamaterial consisting of twin qubits switched over between two different modes.
„In one of the modes, the chain of qubits transmits electronic radiation in the microwave range very well while remaining a quantum element. In another mode, it turns the superconducting phase by 180 degrees and locks the transmission of electromagnetic waves through itself. Yet it still remains a quantum system. So with the help of a magnetic field, such a material can be used as a control element in systems for quantum signals (separate photons) in circuits, from which developing quantum computers consist of”, said Ilya Besedin, an engineer at the NUST MISIS Laboratory of Superconducting Metamaterials and one of the project’s researchers.
It is hard to accurately calculate the properties of one twin qubit on a standard computer compared to the properties of a standard qubit. It is possible to reach the limit of complexity, a level close to or surpassing the capabilities of modern electronic computers, if qubits become several times more complex. Such a complex system can be used as a quantum simulator, i.e. a device that can predict or simulate properties of a certain real process or material.
As the researchers note, they had to sort out lots of theories to correctly describe the processes that occurs in quantum meta-materials.
Source: National University of Science and Technology MISIS

Efectuarea de celule de combustibil pentru o fractiune din costul(Making fuel cells for a fraction of the cost)

descriu dezvoltarea unui material catalitic ieftin și eficient pentru un tip de celulă de combustibil numită celulă de combustibil cu membrană din polimer electrolitic (PEMFC), care transformă energia chimică a hidrogenului în energie electrică și se numără printre cele mai promițătoare tipuri de celule de combustibil pentru motoarele electrice și electronice.Cercetătorii UC Riverside au dezvoltat un material catalitic ieftin și eficient pentru celulele de combustie din polimer electrolitic (PEM), care se numără printre cele mai promițătoare tipuri de celule de combustibil la motoarele electrice și electronice.Materialul pe care l-am creat poate permite producătorilor de automobile să transforme componentele structurale, cum ar fi hota sau șasiul, în elemente funcționale care ajută la alimentarea autovehiculelor”

Posted: Jan 22, 2018

Making fuel cells for a fraction of the cost

(Nanowerk News) Fuel cells have the potential to be a clean and efficient way to run cars, computers, and power stations, but the cost of producing them is limiting their use. That’s because a key component of the most common fuel cells is a catalyst made from the precious metal platinum.
In a paper published today in Small („Electrocatalytic N-Doped Graphitic Nanofiber – Metal/Metal Oxide Nanoparticle Composites”), researchers at the University of California, Riverside, describe the development of an inexpensive, efficient catalyst material for a type of fuel cell called a polymer electrolyte membrane fuel cell (PEMFC), which turns the chemical energy of hydrogen into electricity and is among the most promising fuel cell types to power cars and electronics.
Engineered carbon fibers embedded with active nanoparticles
Engineered carbon fibers embedded with active nanoparticles (top) can be fabricated into structural materials that are lightweight and flexible (bottom). (Image: UC Riverside)
The catalyst developed at UCR is made of porous carbon nanofibers embedded with a compound made from a relatively abundant metal such as cobalt, which is more than 100 times less expensive than platinum. The research was led by David Kisailus, the Winston Chung Endowed Professor in Energy Innovation in UCR’s Marlan and Rosemary Bourns College of Engineering.
Fuel cells, which are already being used by some carmakers, offer advantages over conventional combustion technologies, including higher efficiency, quieter operation and lower emissions. Hydrogen fuel cells emit only water.
Like batteries, fuel cells are electrochemical devices that comprise a positive and negative electrode sandwiching an electrolyte. When a hydrogen fuel is injected onto the anode, a catalyst separates the hydrogen molecules into positively charged particles called protons and negatively charged particles called electrons. The electrons are directed through an external circuit, where they do useful work, such as powering an electric motor, before rejoining the positively charged hydrogen ions and oxygen to form water.
A critical barrier to fuel cell adoption is the cost of platinum, making the development of alternative catalyst materials a key driver for their mass implementation.
Using a technique called electrospinning, the UCR researchers made paper-thin sheets of carbon nanofibers that contained metal ions – either cobalt, iron or nickel. Upon heating, the ions formed ultrafine metal nanoparticles that catalyzed the transformation of carbon into a high-performance graphitic carbon. Subsequently, the metal nanoparticles and residual nongraphitic carbon were oxidized, leading to a highly porous and useful network of metal oxide nanoparticles dispersed in a porous network of graphite.
HFuel Car
UC Riverside researchers have developed an inexpensive, efficient catalyst material for polymer electrolyte membrane (PEM) fuel cells which are among the most promising fuel cell types to power cars and electronics. (Image: BEXIM (CC BY 4.0))
Kisailus and his team, collaborating with scientists at Stanford University, determined that the new materials performed as good as the industry standard platinum-carbon systems, but at a fraction of the cost.
„The key to the high performance of the materials we created is the combination of the chemistry and fiber processing conditions,” Kisailus said. „The remarkable electrochemical properties were primarily attributed to the synergistic effects obtained from the engineering of the metal oxide with exposed active sites and the 3D hierarchical porous graphitic structure.”
Kisailus said an added benefit of the catalytic nanocomposite was that its graphitic fiber nature provided additional strength and durability, which would enable it to serve as both a fuel cell catalyst and potentially as a structural component.
„An important challenge in making high-performance vehicles is reducing weight, both from the body of the vehicle as well as extra weight from the battery or fuel cell, without affecting safety or performance,” he said. „The material we created may enable automakers to turn structural components, such as the hood or the chassis, into functional elements that help power cars.”
Source: University of California – Riverside

Jacheta tactica cu Tweave și Polartec Technology(Beyond Clothing Stretch Alpha Sweater 4-Way-Stretch Insulated Softshell Combat/Tactical Jacket with Tweave and Polartec Technology)

Dincolo de îmbrăcăminte, există o jachetă foarte interesantă, cu 4 căi, izolată, de tip stretch, numită Stretch Alpha Sweater (sau pulover Alpha Stretch), și un exemplu bun al unei softshell izolate pe care a observat-o DefenseReview (DR)

Beyond Clothing Stretch Alpha Sweater 4-Way-Stretch Insulated Softshell Combat/Tactical Jacket with Tweave and Polartec Technology! 

Posted by: David Crane January 21, 2018

Beyond Clothing has a very interesting 4-way stretch insulated softshell jacket called the Stretch Alpha Sweater (or, Alpha Stretch Sweater), and its as good an example of an insulated softshell that DefenseReview (DR) has seen. We actually got to see and handle it at Special Operations Industy Conference (SOFIC) 2017, and came away both intrigued and impressed, especially since we really liked the jacket’s visual design aesthetic, its Manatee Grey (or Gray) color scheme, and its use of premium performance materials like Tweave 4-way stretch fabric, and lightweight Polartech Alpha and possibly also Polartec Power Dry insulation–we’re not quite sure. The product web page says Polartec Alpha, but company rep Rick Elder also mentioned Polartec Power Dry in our video below.

Regardless, this jacket is all premium, and looks like a real luxury in cold environments, especially when you’re engaged in serious activity.

The Beyond Stretch Alpha Sweater currently comes in Grey, Navy and Ranger Green color schemes, and is currently priced at $325.00 USD. Not inexpensive, but also not crazy expensive. This jacket looks and sounds like it’s expensive to make, and appears to DR be a good value for the money.

Defense Review would obviously like to get our hands on one of these for ourselves at some point, as it’s really warm and comfy, not to mention good looking and utilitarian.

Anyway, here are the more detailed particulars on the Stretch Alpha Sweater from the Beyond Clothing page on it:

“A5 – STRETCH ALPHA SWEATER

The perfect garment for active use in cold, wet environments. The Stretch Alpha Sweater combines the warmth and moisture transport of an insulating layer with the durability and mobility of a softshell. The jacket is built out of three layers; starting with a grid fleece that pulls moisture away from the body towards a layer of Polartec® Alpha® Insulation. The Alpha® Insulation traps and retains body heat while continuing to transport moisture to the outer shell where moisture spreads and evaporates. The final layer is a flexible 4-way stretch woven fabric that is highly durable and protects you from the wind and rain. Wear the Stretch Alpha Sweater if you need to stay warm, dry, and protected while on the move.

Details:

Insulated hood
Front zip
Internal left chest pocket
Hand pockets
Materials:

Polartec® Alpha® Insulation – 60g
Polartec® Power Grid® Fleece
Tweave® Durastretch® Nylon with DWR
Benefits:

Breathable
Highly Durable
Water-Resistant
Wind-Resistant
Stretch Construction
Weight: 21.9 oz.

Part No: OM-0188-C10″

Company Contact Info:

THE ACROPOLIS (Beyond Clothing
6363 6th Ave South
Seattle, WA 98108
Phone: 206-767-0307
Email: [email protected]
Website: https://beyondclothing.com

Mill Direct Textiles (MDT) LLC (Polartec Fabrics)
Polartec Phone: 978-686–7700
Mill Direct Textiles Phone: 603-749-7655 (ROLL)
Polartec Website: http://polartec.com
MDT Website: http://www.milldirecttextiles.com

2-D staniu fără flambaj: Un posibil izolator topologic(2-D tin without buckling: A possible topological insulator)

Planar stanene are perspective extraordinare în domeniul electronicii și calculului. „Efectul QSH este destul de delicat, iar cei mai mulți izolatori topologici îl arată doar la temperaturi scăzute”, spune liderul echipei de proiect Guy Le Lay de la Universitatea Aix-Marseille. „Cu toate acestea, stanenul este prevăzut să adopte o stare QSH chiar și la temperatura camerei și mai sus, mai ales atunci când funcționează cu alte elemente.În viitor, sperăm să vedem stanene partenere cu silicen în circuitele de calculatoare.Această combinație ar putea accelera drastic eficiența computațională , chiar și în comparație cu tehnologia de vârf.

Posted: Jan 19, 2018

2-D tin without buckling: A possible topological insulator

(Nanowerk News) Sometimes it pays to be two-dimensional. The merits of graphene, a 2D sheet of carbon atoms, are well established. In its wake have followed a host of „post-graphene materials” – structural analogues of graphene made of other elements like silicon or germanium.
Now, an international research team led by Nagoya University (Japan) involving Aix-Marseille University (France), the Max Planck Institute in Hamburg (Germany) and the University of the Basque country (Spain) has unveiled the first truly planar sample of stanene: single sheets of tin (Sn) atoms. Planar stanene is hotly tipped as an extraordinary electrical conductor for high technology.
Stanene
High-resolution STM image of stanene prepared on a Ag2Sn surface alloy. The honeycomb stanene structure model is superimposed. (Image: Junji Yuhara)
Just as graphene differs from ordinary graphite, so does stanene behave very differently to humble tin in bulk form. Because of relatively strong spin-orbit interactions for electrons in heavy elements, single-layer tin is predicted to be a „topological insulator,” also known as a quantum spin Hall (QSH) insulator. Materials in this remarkable class are electrically insulating in their interiors, but have highly conductive surfaces/edges. This, in theory, makes a single-layered topological insulator an ideal wiring material for nanoelectronics. Moreover, the highly conductive channels at the edge of these materials can carry special chiral currents with spins locked with transport directions, which makes them also very appealing for spintronics applications.
In previous studies, where stanene was grown on substrates of bismuth telluride or antimony, the tin layers turned out to be highly buckled and relatively inhomogeneous. The Nagoya team instead chose silver (Ag) as their host – specifically, the Ag(111) crystal facet, whose lattice constant is slightly larger than that of the freestanding stanene, leading to the formation of flattened tin monolayer in a large area, one step closer to the scalable industrial applications.
Individual tin atoms were slowly deposited onto silver, known as epitaxial growth. Crucially, the stanene layer did not form directly on top of the silver surface. Instead, as shown by core-level spectroscopy, the first step was the formation of a surface alloy (Ag2Sn) between the two species. Then, another round of tin deposition produced a layer of pure, highly crystalline stanene atop the alloy. Tunneling microscopy shows striking images of a honeycomb lattice of tin atoms, illustrating the hexagonal structure of stanene.
The alloy guaranteed the flatness of the tin layer, as confirmed by density-functional theory calculations. Junji Yuhara, lead author of an article by the team published in 2D Materials („Large area planar stanene epitaxially grown on Ag(1 1 1)”), explains: „Stanene follows the crystalline periodicity of the Ag2Sn surface alloy. Therefore, instead of buckling as it would in isolation, the stanene layer flattens out – at the cost of a slight strain – to maximize contact with the alloy beneath.” This mutual stabilization between stanene and host not only keeps the stanene layers impeccably flat, but lets them grow to impressive sizes of around 5,000 square nanometers.
Planar stanene has exciting prospects in electronics and computing. „The QSH effect is rather delicate, and most topological insulators only show it at low temperatures”, according to project team leader Guy Le Lay at Aix-Marseille University. „However, stanene is predicted to adopt a QSH state even at room temperature and above, especially when functionalized with other elements. In the future, we hope to see stanene partnered up with silicene in computer circuitry. That combination could drastically speed up computational efficiency, even compared with the current cutting-edge technology.”
Source: Nagoya University

Un nanofenomen care declanșează procesul de reparare a oaselor(A nanophenomenon that triggers the bone-repair process)

Aceste rezultate au promisiunea pentru industria protezelor, în care noi materiale care reproduc sau amplifică acest efect flexoelectric pot fi folosite pentru a ghida regenerarea tisulară, conducând la o asimilare mai reușită a implanturilor.Prin studierea gradientilor de tulpina in oase si minerale osoase pure (hidroxiapatita), cercetatorii au fost in masura sa calculeze magnitudinea exacta a acestui camp electric. Descoperirile lor indică faptul că este suficient de mare în interiorul celor 50 microni necesari pentru vârful crackului, pentru a fi detectat de către celulele responsabile de repararea oaselor, implicând direct în acest proces flexoelectricitatea.

Posted: Jan 19, 2018

A nanophenomenon that triggers the bone-repair process

(Nanowerk News) Researchers at the Institut Català de Nanociència i Nanotecnologia (ICN2), a Severo Ochoa research centre located in the Universitat Autònoma de Barcelona (UAB) Campus and member of the Barcelona Institute of Science and Technology (BIST), have discovered that bone too is flexoelectric. They posit the possible role of flexoelectricity in the regeneration of bone tissue in and around the kind of microfractures incurred in bones on a daily basis.
The ICN2 Oxide Nanophysics Group led by ICREA Prof. Gustau Catalan reports these findings today in Advanced Materials („Flexoelectricity in Bones”), with lead author Fabián Vásquez-Sancho. The work has potential implications for the prosthetics industry and the development of biomimetic self-healing materials.
micro-cracks in bone mineral
Strain gradients can be large around small defects such as micro-cracks in bone mineral, so gradient-induced electricity (flexoelectricity) is also expected to be large around such defects.
Bones were already known to generate electricity under pressure, stimulating self-repair and remodelling. First reported in the late fifties, this was initially attributed to the piezoelectricity of bone’s organic component, collagen. However, studies have since observed markers of bone repair in the absence of collagen, suggesting that other effects are at play. In this work ICN2 researchers have revealed just such an effect: the flexoelectricity of bone’s mineral component.
Flexoelectricity is a property of some materials that causes them to emit a small voltage upon application of a non-uniform pressure. This response is extremely localised, becoming weaker as you move away from the point of maximum stress. In microfractures it is localised to the leading edge or tip of the crack, an atomically small site that, by definition, concentrates the maximum strain a material is able to withstand before full rupture. The result is a flexoelectric field of such magnitude that, in the immediate vicinity of the crack, it eclipses any background collagen piezoelectric effect.
By studying strain gradients in bones and pure bone mineral (hydroxyapatite), the researchers have been able to calculate the precise magnitude of this electric field. Their findings indicate that it is sufficiently large within the required 50 microns of the crack tip to be sensed by the cells responsible for bone repair, directly implicating flexoelectricity in this process.
Furthermore, since the cells responsible for synthesising new bone tissue (osteoblasts) are known to attach close to the tip, it would appear that the electric field distribution signals this point as the centre of damage, becoming a moving beacon for repair efforts as the crack is healed.
These results hold promise for the prosthetics industry, where new materials that reproduced or amplified this flexoelectric effect could be used to guide tissue regeneration, leading to a more successful assimilation of implants.
Source: Universitat Autonoma de Barcelona