Category Archives: Material science

Can We Manipulate Matter Like Thanos? (Quantum / Superhero)

Being able to manipulate matter has been a long-standing goal in material science. Would it not be amazing if we could control matter on the grand scale that Thanos does when in possession of the Infinity Stones in Avengers: Infinity War? Now, Ravensteijn and colleagues evaluated how far mankind has come in the pursuit of Thanos-like matter manipulation powers. Their study appeared in the Journal Superhero Science and Technology.

They have shown that controlling matter, regardless of the length scale, requires control over the forces between objects. To control large (macroscopic) objects, a large amount of energy is needed. One way to control such objects is to acquire the Infinity Gauntlet complete with the six Infinity Stones, just like Thanos in Avengers: Infinity War. But, we can now mimic part of Thanos’ control over matter at the colloidal scale.

“We can now make a wide range of colloidal particles with tunable responsiveness, patchiness, shapes, and sizes. By controlling the interparticle forces, we can manipulate billions (yes billions!) of colloids at the same time by varying triggers such as temperature, pH, and light.”

— authors of the study.

What are colloidals?

The world of colloids lies between atoms and the objects. Colloidal materials consist of a large number of small particles such as solid particles, gas bubbles, or liquid droplets, that are mixed through a medium (such as a liquid, gas or solid). Due to their small dimensions, the earth’s gravity has little to no effect on these particles. This means that colloids dispersed in a medium do not (or barely) sink to the bottom of the container in which you keep them. However, this does not imply that colloids are immobile. Colloids are continuously moving, a phenomenon that scientists refer to as Brownian motion. These movements are the result of constant collisions between molecules of the dispersing medium (such as water molecules) and the colloids.

Figure 1. Schematic representation of the dimensions of objects ranging from the molecular/atomistic world to the macroscopic world. Representative examples of objects from life (real world and the MCU) are depicted to illustrate the specific length scales. The red triangular arrows depict the contribution of thermal motion and gravitational forces for objects with different characteristic dimensions. The colloidal domain ranges from roughly 10¯8 to 10¯6 m and is highlighted on the diagram. © Ravensteijn et al.

What scientists achieved?

Similar to Thanos’ ability to modify matter with by activating or triggering the appropriate Infinity Stone in the Infinity Gauntlet, colloid scientists started to study colloidal systems that can switch between the assembled and disassembled states, or even between assemblies with different internal structures. A popular and successful route for scientists towards these responsive particles is to decorate the surface of the colloids with molecules that can feel and respond to external changes or triggers in the environment, such as changes in pH, temperature, or the level of illumination with particular types of light (Figure 2).

Figure 2. Illustration of responsive colloidal systems. Upon applying Trigger i, e.g., a change (Δ) in pH, temperature, or illumination with UV light, the particles are switched from a non-interacting (left) to an activated state (right). In the active state assembly takes place. The assembly can be disintegrated by applying Trigger ii. Controlling these triggers is analogous to Thanos activating an Infinity Stone to manipulate matter. Switching between the disassembled and assembled state can be followed by microscopy or even macroscopic color changes. Scale bars: 5 μm. Microscopy images were adapted from ref. 50. 2015, Nature Publishing Group. © Ravensteijn et al.

Initially, the particles are not drawn to each other (they are in a non-interactive state). But, applying a trigger creates an attractive force between the particles that eventually leads to the creation of hierarchical structures. Applying a second trigger (or stopping the first one), removes the attraction between the particles and the assembly gradually falls apart again. This is a genuine “activation of the appropriate Infinity Stone” moment to manipulate colloids.

“In contrast to the instantaneous changes Thanos can make with his gauntlet, the assembly and disassembly of colloidal particles generally takes some time. A little patience is required to allow the colloids to find or move away from each other via Brownian motion. The time required for (dis)assembly can vary from seconds to hours and depends on the particle concentration and the strength of the attractive or repulsive forces generated by the applied triggers.”

— authors of the study.

Finally, scientists proved that, to manipulate matter, the Infinity Stones are not strictly necessary. There is no need to roam the universe for the stones just like Thanos did in Avengers: Infinity War. The answer may very well be right in front of us, and at the microscopic scale. The answer is colloids.


Reference: van Ravensteijn, B. G., Magana, J. R., & Voets, I. K. (2020). Manipulating matter with a snap of your fingers: A touch of Thanos in colloid science. Superhero Science and Technology, 2(1), 19–30. https://doi.org/10.24413/sst.2020.1.5329


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‘Smart’ Fabric That Can Stiffen on Demand (Material Science)

Scientists from Nanyang Technological University, Singapore (NTU Singapore) and the California Institute of Technology (Caltech), United States, have developed a new type of ‘chain mail’ fabric that is flexible like cloth but can stiffen on demand. 

The lightweight fabric is 3D-printed from nylon plastic polymers and comprises hollow octahedrons (a shape with eight equal triangular faces) that interlock with each other.

When the soft fabric is wrapped within a flexible plastic envelope and vacuum-packed, it turns into a rigid structure that is 25 times stiffer or harder to bend than when relaxed. The physical principle behind it is called “jamming transition”, similar to the stiffening behaviour in vacuum-packed bags of rice or beans.

Known as ‘wearable structured fabrics’, the development could pave the way for next-generation smart fabrics that can harden to protect a user against an impact or when additional load-bearing capacity is needed.

Potential applications may include bullet-proof or stab-proof vests, configurable medical support for the elderly, and protective exoskeletons for high-impact sports or workplaces like construction sites.

Published today (11 Aug 2021, 11am EST) in Nature, this interdisciplinary research results from a collaboration between experts in mechanical engineering and advanced manufacturing.

Lead author of the paper, Nanyang Assistant Professor Wang Yifan, said that their research has fundamental significance as well as industrial relevance and that it could lead to a new platform technology with applications in medical and robotic systems that can benefit society.

“With an engineered fabric that is lightweight and tuneable – easily changeable from soft to rigid – we can use it to address the needs of patients and the ageing population, for instance, to create exoskeletons that can help them stand, carry loads and assist them with their daily tasks,” said Asst. Prof Wang from NTU’s School of Mechanical and Aerospace Engineering, who started this research when he was a post-doc researcher at Caltech.

“Inspired by ancient chain mail armour, we used plastic hollow particles that are interlocked to enhance our tuneable fabrics’ stiffness. To further increase the material’s stiffness and strength, we are now working on fabrics made from various metals including aluminium, which could be used for larger-scale industrial applications requiring higher load capacity, such as bridges or buildings.”

Corresponding author of the paper, Professor Chiara Daraio, Caltech’s G. Bradford Jones Professor of Mechanical Engineering and Applied Physics, said, “We wanted to make materials that can change stiffness on command. We’d like to create a fabric that goes from soft and foldable to rigid and load-bearing in a controllable way.”

An example from popular culture would be Batman’s cape in the 2005 movie Batman Begins, which is generally flexible but can be made rigid at will when the caped crusader needs it as a glider.

The science behind the interlocking fabric

The scientific concept behind the variable-stiffness fabric is called “jamming transition”. This is a transition in which aggregates of solid particles switch from a fluid-like soft state to a solid-like rigid state, with a slight increase in packing density. However, typical solid particles are usually too heavy and do not provide enough tensile resistance for wearable applications.

In their research, the authors designed structured particles – where each particle is made of hollow frames – in the shape of rings, ovals, squares, cubes, pyramids and different shapes of octahedrons that are then interlocked together. These structures, known as topologically interlocked structures, can then be formed into chain mail fabric that has a low density and yet high tensile stiffness, using state-of-the-art 3D printing technology to print them as a single piece.

They then modelled the number of average contact points per particle and how much each structure will bend in response to the amount of stress applied. The team discovered that by customising the particle shape, there was a trade-off between how much weight the particles will have versus how much the fabric can bend, and how to balance the two factors.

To add a way of controlling the stiffness of the fabric, the team encapsulated the chain mail fabric in a flexible plastic envelope and compacted the fabrics using a vacuum, which applies pressure from the outside. The vacuum pressure increases the packing density of the fabric, causing each particle to have more contact with its neighbours, resulting, for the octahedron-based fabric, in a structure that is 25 times more rigid. When formed into a flat, table-shaped structure and vacuum-locked in place, the fabric could hold a load of 1.5kgs, more than 50 times the fabrics’ own weight.

In another experiment, the team dropped a small steel ball (30 grams, measuring 1.27cm in diameter) onto the chain mail at 3 metres per second. The impact deformed the fabric by up to 26 mm when it was relaxed, but by only 3 mm when it was stiffened, a six times reduction in penetration depth.

To show the possibilities of their fabric concept using different source material, the team 3D-printed the chain mail using aluminium and demonstrated that it has the same flexibility and ‘soft’ performance as nylon when relaxed and yet it could also be ‘jammed’ into structures that are much stiffer compared to nylon due to aluminium’s higher stiffness and strength.

These metallic chain mails could be used in applications such as body armour, where they must protect against hard and high-speed impacts from sharp objects. In such a case, the encapsulation or envelope material could be made from aramid fibres, commonly known as Kevlar, used as a fabric in bulletproof vests.

Moving forward, the team is looking to improve the material and fabric performance of their chain mail and to explore more methods of stiffening it, such as through magnetism, electricity or temperature.

Research paper titled “Structured fabrics with tunable mechanical properties”, published in Nature, 11-Aug-2021. DOI: 10.1038/s41586-021-03698-7

Featured image: NTU Asst Prof Wang Yifan bending the nylon chain mail, encased in a plastic envelope and vacuum-packed, which makes it 25 times stiffer than usual. © NTU Singapore


Provided by NTU Singapore

Quantum Materials Cloak Thermal Radiation (Material Science)

The Science

Scientists demonstrated that ultrathin films of samarium nickel oxide can mask the thermal radiation emitted by hot materials. Samarium nickel oxide is a quantum material. These are materials that have strange and incredible properties due to quantum mechanics. The cloaking mechanism is due to the material undergoing a unique, gradual transition from insulator to heat-conducting metal. This transition occurs over a temperature range from 100 to 140 degrees centigrade.

The Impact

This study shows that quantum materials can manage thermal radiation. This ability could advance applications such as infrared camouflage, privacy shielding, and heat transfer control. The 100-140 degree centigrade heat range is important because it can be seen with infrared cameras.

Summary

Conventional wisdom states that the hotter an object is, the brighter it glows. This is the case for thermal light at any wavelength and enables applications such as infrared imaging and noncontact thermometry. However, researchers at the Department of Energy (DOE) Center for Functional Nanomaterials at Brookhaven National Laboratory demonstrated a coating that emits the same amount of thermal radiation regardless of temperature, within a temperature range of about 30 degrees centigrade. This is accomplished using samarium nickel oxide—a quantum material that changes strongly but gradually as a function of temperature. This is the first time researchers have demonstrated temperature-independent thermal radiation. The results have substantial implications for infrared camouflage, privacy shielding, and radiative heat transfer.

Funding

This research was supported by Office of Naval and the National Science Foundation, the Air Force Office of Scientific Research, and a Critical Skills Master’s Fellowship from Sandia National Laboratories. Some measurements were performed at the Soft Materials Characterization Laboratory at the University of Wisconsin–Madison. This research used resources of the Center for Functional Nanomaterials and National Synchrotron Light Source II, both of which are DOE Office of Science user facilities at Brookhaven National Laboratory.

Publications

Shahsafi, A., et al.,Temperature-independent thermal radiationProceedings of the National Academy of Sciences 116, 26402 (2019). [DOI: 10.1073/pnas.1911244116]

Featured image

Thermal images of samples heated from 100 to 140 degrees C. The top row shows a material heating with increasing temperature. The bottom row shows the same material coated with ultrathin samarium nickel oxide films that cloak the thermal emission.Image courtesy of paper author A. Shahsafi, University of Wisconsin-Madison


Provided by DOE

It Was Figured Out How To Dispose of Metallurgical Slag (Material Science)

Researchers at Ural Federal University (UrFU) and the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (UrB RAS) have developed and successfully tested technology for waste-free processing of slag (electric arc and ladle). This technology helps obtain valuable materials, cast iron, Portland cement clinker. The main thing is that it helps to eliminate the problem of environmental pollution by industrial enterprises. An article describing the technology was published in the journal Steel in Translation.

“Our technology allows completely dispose of the two types of slags. It helps to solve the problem of anthropogenic pressure on the environment,” said Oleg Sheshukov, Chief Researcher at UrFU and RAS, head of the scientific group. “It is especially important that we achieved complete processing of the out-of-furnace slag. Since it contains very little iron, such slag is usually not reused, but sent to waste dumps, constantly increasing the damage to the environment.”

Technology development and testing consist of several stages. Most often, ladle slag is a dust fraction that is unsuitable for use in processing processes. Therefore, first of all, scientists stabilized the ladle slag in a solid-state. For this, borate glass was added to it – a cheap waste material that also requires recycling.

The clinker obtaining from ladle slag is a more complex technological task than the pig iron obtaining from an electric furnace. Therefore, the researchers first calculated the conditions necessary for the production of clinker. These are the chemical composition of the processed mixture (charge) and the temperature range. Then, with the help of crushing and mixing, they obtained a charge with admixtures of silicon and aluminum-containing minerals alite, belite, celite, and brownmillerite. At the laboratory, the briquetted charge was heated in a furnace up to 1500-1600 degrees Celsius, until it completely melted, kept, and then slowly cooled. The experiments made it possible to find out that the clinker, in terms of the quality corresponding to state standard, is formed from five slag compositions at a 10-minute exposure at a temperature of 1540-1560 degrees Celsius.

At the next stage, at the Seversky Pipe Plant (Russia), researchers selected samples of waste from the electric furnace production that were similar in structure. These samples contain a high iron content. As a result of several laboratory melts – using coke as a carbonaceous reductant of iron simultaneously with Portland cement clinker – the scientists obtained cast iron, which also satisfies the requirements of state standard. At the same time, all raw materials were processed into commercial products.

The technology of joint waste-free production of pig iron and Portland cement clinker was successfully tested at the production of the Klyuchevskoy Ferroalloy Plant (Russia). In the course of test heats, the developers came to the conclusion that in order to avoid overheating and in order to control temperatures and save money, a cheaper rotary tilt furnace should be used, not an arc furnace. Clinker is formed from the charge, which was fed into the rotary tilting furnace, as a result of mixing, reduction, and melting, cast iron, and slag residue. Subsequent mixing of clinker with gypsum dihydrate and firing the mixture in a kiln resulted in the formation of Portland cement, the most widely used type of cement.

Industrial enterprises of Russia and Kazakhstan are interested in the technology, the developers say.

Note

One of the most important problems of metallurgical enterprises around the world is the disposal of production wastes, among which the main share falls on metallurgical slag which appeared during metal smelting. Billions of tons of slags from ferrous and non-ferrous metallurgy fill vast areas. According to scientists, the volume of slag dumps throughout the planet is annually increasing by 200-300 million tons.

Dumps pollute the environment and worsen the ecological situation. For example, ladle slag is a toxic, fine-grained dust-like powder that easily flies over long distances and then dissolves in sedimentary and groundwater. At the same time, ferrous metallurgy slags, mainly electric furnaces, contain up to 10% metallic and about 30% oxide iron, as well as magnesium, aluminum, silicon, phosphorus, calcium, and lime. Recycling and re-using slags in production will help not only reduce environmental impact but also contribute to solving the problem of depletion of mineral resources.

Featured image: According to Oleg Sheshukov, the technology allows for the complete utilization of two types of slags. © UrFU


Reference: Sheshukov, O.Y., Egiazar’yan, D.K. & Lobanov, D.A. Wasteless Joint Processing of Ladle Furnace and Electric Arc Furnace Slags. Steel Transl. 51, 156–162 (2021). https://doi.org/10.3103/S0967091221030116


Provided by Ural Federal University

Alginic Acid Improves Artificial Bones, Study Shows (Material Science)

Osaka City University study shows how alginic acid improves artificial bones in 3 ways

New research shows that mixing low viscosity alginic acid with calcium phosphate cement (CPC), a material commonly used as a bone replacement, confers 3 functional improvements: shorter setting time, increased compressive strength, and acquisition of porosity.

One reason for the increased use of CPC in recent years is its self-setting nature, allowing it to be injected into a patient for a more non-invasive approach. However, CPCs have a dense microstructure that make it difficult for cells to enter. This lack of pores limits the potential for new bone growth. This study, published in the Journal of Materials Science: Materials in Medicine, explores the effect the naturally derived biopolymer alginic acid has on this issue.

Previous research has studied other biopolymers, including gelatin, collagen, and chitosan, but this joint study between the Osaka City University (OCU), Graduate School of Medicine and Graduate School of Engineering, has confirmed the positive effects of mixing alginic acid with CPC. In vitro studies showed alginic acid shorten setting time and increase compressive strength of CPC. In addition, in vivo studies showed the biopolymer increase porosity of CPC, allowing cells to enter and new bone to grow.

Alginic acid has been widely used in the medical field for procedures such as, cell immobilization, drug delivery, and wound dressing. However, there have been limited studies in conjunction with CPC. The degradability and cross-linking characteristics of alginic acid make it a promising additive to improve on the dense and generally poor mechanical properties of CPC.

This new study evaluated a series of CPC-alginate (the salt form of alginic acid) compounds with increasing amounts of alginic acid. In vitro, a pH meter showed a decrease in pH levels as alginic acid amounts increased, speeding up setting time. Scanning electron microscopy revealed that compounds with increased alginic acid had more pores and less density. In vivo, X-ray and micro-CT analysis showed that femurs injected with CPC compounds of increased amounts of alginic acid had, after 6 weeks, more degradation and bone formation than the control group.

“Artificial bones can support broken bones, but they do not replace our own bones and remain in the body as a foreign object” said Graduate Student Akiyoshi Shimatani, and first author of the study. Associate Professor Hiromitsu Toyoda of the OCU Dept. of Orthopedic Surgery continued: “To solve this problem, we have developed an artificial bone in collaboration Professor Yoshiyuki Yokogawa and his team from the OCU Faculty of Engineering, which is sticky, hard to break, and replaces the body’s own bone. We hope this becomes a new option for artificial bones.”

Featured image: Cross sectional microstructures in the set CPC samples (a) without and (b) with alginate (20 wt%). Little porosity was detected in CPC sample without alginate (a1). Adding alginate resulted in the formation of macropores within the bulk materials (b1) © Akiyoshi Shimatani、Hiromitsu Toyoda、Kumi Orita、Yuta Ibara、Yoshiyuki Yokogawa、Hiroaki Nakamura


Reference: Shimatani, A., Toyoda, H., Orita, K. et al. A bone replacement-type calcium phosphate cement that becomes more porous in vivo by incorporating a degradable polymer. J Mater Sci: Mater Med 32, 77 (2021). https://doi.org/10.1007/s10856-021-06555-1


Provided by Osaka University

The Movement of Small Water Droplets Is Controlled By Means Of A Magnet (Material Science)

The Microfluidics Cluster of the UPV/EHU-University of the Basque Country has created a paramagnetic ring that encapsulates water droplets under a magnetic field

A study carried out by the UPV/EHU’s Microfluidics Cluster, published by the prestigious journal Advanced Functional Materials, has presented and characterised the formation and properties of a superparamagnetic ring, which fits snugly around a drop of water due to liquid-liquid interaction, and allows the drops to be physically manipulated. The study is part of the European MAMI project, which involves multidisciplinary groups and companies from six countries.

Droplet manipulation is kindling great interest in several fields, including technological applications and basic studies in dynamic systems. The Lab-on-a-chip and microfluidics community is particularly interested in the precise manipulation of small volumes of fluids, droplet microfluidics. A piece of research conducted by the UPV/EHU’s Microfluidics Cluster has found that a superparamagnetic ring forms spontaneously around a water droplet when an oil-based ferrofluid is in contact with the droplet under the influence of a magnetic field and varies according to the strength of the magnetic field applied.

The ring consists of an oil-based ferrofluid, a stable suspension of ferromagnetic particles in an oil phase. It appears spontaneously due to the oil-water interfacial interaction under the influence of a magnetic field. “The ferrofluid-water interaction resembles a cupcake, with the surrounding ring only at the base of the droplet,” explained the Ikerbasque professor Lourdes Basabe, who leads the cluster. The ring is analogous to a soft matter ring magnet, “which stabilises the droplets on a surface, and prevents them from mixing. And these water droplets can move with precision by displacing the external magnetic field,” she added.

UPV/EHU lecturer Fernando Benito-López, the cluster’s lead researcher, explained that “under a magnetic field the water droplets can be encapsulated in the ferrofluid, and be moved remotely by moving a magnet, thanks to the magnetic properties of the ferrofluid. Even when two or more cupcakes are mechanically joined together, the water droplets do not mix, because their ferrofluid rings fuse together to form an isolating physical barrier. Moreover, as it is paramagnetic, if the magnet is removed, if the magnetic field is removed, the effect disappears, in other words, it is a switchable structure, and these drops can be mixed by switching off the magnetic field. Likewise, this assembly could be formed on top of a substrate or, like a hanging cupcake, on the underside of a substrate”. These are millimetre-sized droplets, which contain volumes on a microlitre scale, and “so multiple possibilities are opened up for handling such small volumes,” he added.

A new, advantageous approach to open-surface droplet microfluidics

Both researchers assert that this finding “makes possible the robust, controllable and programmable manipulation of the enclosed water droplets. This work opens the door to new applications in inverted or open-surface microfluidics, lays the foundations for new studies into interactions between two immiscible liquids and could lead to new studies, a new piece of knowledge relating to liquid-liquid interaction. They also reveal that the use of this ring to manipulate a hanging droplet is the first example of the magnetic manipulation of droplets on an inverted surface, thus opening up the way to new applications.

This is basic research that may have currently unknown applications, but for the time being they list a number of possibilities, such as “the development of sensing devices for liquids, chemical reactions on the microscale with small amounts of reagents, analysis of individual cells, detection of substances in aerosols, etc.”.

Now, “we want to find out how small these droplets can be. We would like to explore the development of new microfluidic technologies, in other words, the manipulation of very small volumes, or develop the systems generated through this project to produce fluid analysis devices based on magnetic properties, or at least exploit those properties in some way,” they said.

The researchers are grateful for the European funding obtained thanks to the European MAMI project, “an international training network for PhD students, formed by a consortium of research groups and multidisciplinary companies from six countries to develop new technologies around the use of magnetic materials, which has allowed us to recruit people who are very highly motivated”. They are also delighted that this great discovery has been made “in a young research group, which shows that top-level research can be carried out at the UPV/EHU”.

Featured image: Researchers from the UPV/EHU’s Microfluidics Cluster. Photo: UPV/EHU.


Reference: Nasirimarekani, V., Benito-Lopez, F., Basabe-Desmonts, L., Tunable Superparamagnetic Ring (tSPRing) for Droplet Manipulation. Adv. Funct. Mater. 2021, 31, 2100178. https://doi.org/10.1002/adfm.202100178


Produced by The University Of Basque Country Magazine

Unravelling How Ions Move in Phosphate Glass (Material Science)

Phosphate glass is a versatile compound that has generated interest for its use in fuel cells and as biomaterials for supplying therapeutic ions. P2O5-the compound that forms the structural network of phosphate glass, is made up of phosphorus, an element that can adopt many different bonding configurations in combination with oxygen.

The physicochemical properties crucial for the real-life applicability of phosphate glassーfor instance, the hydration reaction dictating how quickly a phosphate glass-based biomaterial will dissolve inside the bodyーdepends on the diffusion of ions into the glass. Thus, to improve the physicochemical properties of phosphate glasses, it is important to understand the relationship between the structure and ion diffusion. However, studying such interactions at the atomic level is extremely difficult, prompting scientists to search for a suitable approach to illuminate the details of the ion diffusion process.

Recently, a team of researchers from Nagoya Institute of Technology, Japan, led by Dr. Tomoyuki Tamura, has theoretically deciphered the ion diffusion mechanism involved in the hydration reaction process of phosphate glasses. Their study has been published in the Physical Chemistry Chemical Physics journal.

In fully connected P2O5-based phosphate glass, three of the oxygen atoms in each phosphate unit are bonded to neighboring phosphorous atoms. To study the dynamics of ions in the phosphate glass during the hydration process, the researchers used a model made of phosphates with QP2 and QP3 morphologies, that contain two and three bridging oxygens per PO4 tetrahedron, respectively, along with six coordinated silicon structures.

The researchers implemented a theoretical computational approach known as “first-principles molecular dynamic (MD) simulation” to investigate the diffusion of proton and sodium ions into the glass. Explaining the rationale for their unconventional approach, Dr. Tamura says, “First-principles MD simulation enabled us to assume the initial stage of water infiltrating and diffusing into silicophosphate glass and elucidate the diffusion of protons and inorganic ions for the first time.”

Based on their observation, the researchers proposed a mechanism where the protons “hop” and are adsorbed onto the non-bridging oxygen or “dangling” oxygen atom of nearby phosphates through hydrogen bonds. However, in the phosphate glass model they used, the QP2 phosphate units contributed more strongly to the diffusion of protons than the QP3 phosphate units. Thus, they found that the morphology of the phosphate network structure, or the “skeleton” of the glass, greatly affects the diffusion of ions. They also noticed that when a sodium ion was present in the vicinity, the adsorption of a proton onto a QP2 phosphate unit weakened the electrostatic interaction between sodium and oxygen ions, inducing the chain diffusion of sodium ions.

The demand for new biomaterials for effective prevention and treatment is on the rise, and phosphate glasses are well-poised to fulfill this growing need. A large proportion of the population, comprising both elderly and younger people, suffers from diseases related to bone and muscle weaknesses. As Dr. Tamura surmises, “Water-soluble silicophosphate glass is a promising candidate for supplying drugs or inorganic ions that promote tissue regeneration, and our study takes the research in glass technology one step nearer towards realizing the goal.

Thus, the researchers’ novel insights are bound to have profound real-life impact and lead to breakthroughs in research on fuel cells and bioresorbable materials!

Featured image: Scientists use first-principles molecular dynamics to decipher ion diffusion dynamics in phosphate glass structures.
Investigating the microscopic diffusion mechanism of protons and sodium ions in phosphate glasses via first-principles molecular dynamics simulation indicates the key role of the morphology of the phosphate network structure on the diffusion of ions. Image Credit: Tomoyuki Tamura from Nagoya Institute of Technology


Reference

  • Title of original paper: Diffusion of protons and sodium ions in silicophosphate glasses: insight based on first-principles molecular dynamic simulations
  • Journal: Physical Chemistry Chemical Physics
  • DOI: 10.1039/d1cp01646f

Provided by Nagoya Institute of Technology

Metamaterials Research Challenges Fundamental Limits in Photonics (Material Science)

Cornell researchers are proposing a new way to modulate both the absorptive and the refractive qualities of metamaterials in real time, and their findings open intriguing new opportunities to control, in time and space, the propagation and scattering of waves for applications in various areas of wave physics and engineering.

The research published in the journal Optica, “Spectral causality and the scattering of waves,” is authored by doctoral students Zeki Hayran and Aobo Chen, M.S. ’19, along with their adviser, Francesco Monticone, assistant professor in the School of Electrical and Computer Engineering in the College of Engineering.

The theoretical work aims to expand the capabilities of metamaterials to absorb or refract electromagnetic waves. Previous research was limited to modifying either absorption or refraction, but the Monticone Research Group has now shown that if both qualities are modulated in real time, the effectiveness of the metamaterial can be greatly increased.

These temporally modulated metamaterials, sometimes referred to as “chrono-metamaterials” may open unexplored opportunities and enable technological advances in electromagnetics and photonics.

“What we demonstrate,” Monticone said, “is that if you modulate both properties in time, you manage to absorb electromagnetic waves much more efficiently than in a static structure, or in a structure in which you modulate either one of these two degrees of freedom individually. We combined these two aspects together to create a much more effective system.”

The findings may lead to the development of new metamaterials with wave absorption and scattering properties that far outperform what is currently available. For example, a broadband absorber has to be thicker than a certain value to be effective, but the material thickness will limit the applications of the design.

“To decrease the thickness and increase the bandwidth of such an absorber, you have to overcome the limitations of conventional materials,” Hayran said. “One of the ways to bypass these limitations is through temporally modulating the structure.”

The aim of Monticone’s group is to open new areas of research to produce increasingly efficient practical applications.

“What we are trying to do is not incremental changes to the technology,” Monticone said. “We want disruptive changes. That’s really what motivates us. So how can we make a dramatic improvement to the technology, not just an incremental improvement? To do that, very often, you have to go back to the fundamentals.”

The new research pushes the limits of electromagnetic wave absorption by using another degree of freedom, which is modulation in time, something not typically done in this area, but now receiving increasing research attention.

With a new theoretical underpinning in place, experimentally implementing temporal modulations of this kind is the challenge for further research. A physical experiment would first need to design a mechanism to control the modulation of absorptive and refractive qualities of a material over time, which might include laser beams or microwave components.

The ideas have direct implications for several applications, such as broadband radar absorption and temporal invisibility and cloaking. Applications could also extend to other domains of wave physics such as acoustics and elastodynamics.

“Our findings, and the exciting results by other researchers working in this area, highlight the many opportunities offered by time-varying metamaterials for both classical and quantum electromagnetics and photonics,” Monticone said.

This research is supported by the Air Force Office of Scientific Research and the National Science Foundation. Additional support is provided through the Fulbright Foreign Student Program of the U.S. Department of State.


Reference: Zeki Hayran, Aobo Chen, and Francesco Monticone, “Spectral causality and the scattering of waves,” Optica 8, 1040-1049 (2021). https://doi.org/10.1364/OPTICA.423089


Provided by Cornell University

Impermeable Graphene Oxide Protects Silicon from Oxidation (Material Science)

Curtin University researchers have found applying a thin invisible layer of graphene oxide to silicon forms an impermeable barrier, which could be used to protect artwork, prevent corrosion of metals, and produce higher efficiency solar cells.

Lead author Dr Nadim Darwish from Curtin’s School of Molecular Life Sciences said while protective layers on silicon were already used as an efficiency enhancer in devices such as solar cells and microchips, the procedure for forming these protective coatings was complicated and required highly specialised fabrication laboratories.

“Silicon solar cells often require the application of a layer of alumina, silica or other material to increase their efficiency in transforming sunlight to electricity. Our breakthrough was finding that graphene oxide reacts quickly with silicon without the need for external catalysts, additives or complicated procedures,” Dr Darwish said.

“We found the graphene oxide protects silicon from ambient oxygen for at least 30 days, which is a significant step forward in applying the properties of 2D materials such as graphene and graphene oxide to make silicon even more efficient and useful.”

Research co-author PhD student Soraya Rahpeima, also from Curtin’s School of Molecular Life Sciences said the new method could potentially enable development of new types of solar cells for more efficient generation and supply of power along with many applications in electronics.

“This breakthrough opens a whole new realm of possibilities even beyond silicon research,” Ms Rahpeima said.

“For example, graphene and graphene oxide can be used to protect sensitive materials from gases and ambient environments including ultraviolet light.

“A thin, invisible, and flexible layer when applied to artwork such as valuable paintings and stamps could potentially protect them from harmful light and moisture and other damaging elements contained in air without the need to cover the artwork with thick glass or protective layers that diminish the beauty of the artwork.”

The paper, ‘Impermeable Graphene Oxide Protects Silicon from Oxidation’, was published in journal ACS Advanced Materials & Interfaces can be found online here.

The paper was co-authored by Associate Professor Simone Ciampi and PhD student Essam Dief, both from Curtin’s School of Molecular Life Sciences and Professor Colin Raston from Flinders University.


Provided by Curtin University