Engineering and Technology Updates
Balancing sustainability, safety and comfort in engineered floor slabs
Using less material in floors is a viable strategy for improving sustainability in buildings, as it can reduce the structure’s environmental footprint. Prioritizing only this goal, however, can lead to unwanted effects — such as an echo in a room or noise traveling between floors, according to Nathan Brown, assistant professor of architectural engineering. Penn State researchers explored a method for optimizing the acoustic and structural properties of concrete floor slabs. “The exciting result of our research is that shaped structures can improve sound insulation performance in buildings while reducing the embodied carbon emissions of the structural system,” said Jonathan Broyles, an architectural engineering doctoral candidate and the first author of the paper. To begin their investigation, the team used 3D modeling software to create shaped concrete slabs made up of many curves connected by movable control points. By providing the program with parameters to follow when moving these points, the researchers allowed the software to generate a variety of possible designs with realistic, customized constraints. Continuing the effort to find a favourable design — a process called optimization — the researchers needed to test the generated designs’ performance in two areas. They analyzed structural properties, for meeting building engineering standards, and acoustic properties, for minimizing undesirable sounds. “Traditional optimization is focused on targeting one value as a good or bad design, but in this case, we have two values: one to evaluate structural performance and another for acoustic performance,” said Brown, corresponding author on the paper. “We set up a model with some variables and used a computer algorithm to move through potential designs, targeting better options for both values at the same time.” The team used a number of equations to inform their optimization constraints. In addition to considering mass, with a goal of reducing mass to reduce the emissions required to make and install a slab, the researchers also took shape and stiffness into account. Understanding the effect of each of these variables on acoustic properties would allow the team to reduce the power of transmitted sound waves hitting the slab, according to Brown. Using optimization, the researchers identified concrete slab designs that used less concrete than a conventionally shaped slab and maintained desirable acoustic properties. These findings, Brown said, build a foundation for the design of shaped concrete floors that can be optimized for better interaction with sound without compromising sustainability. The team plans to apply the methods used in this research to understand the trade-offs between sustainability and performance in areas beyond acoustics. According to Brown, exploring this connection can lead to more sustainable buildings that do not compromise quality of life.
Tiny magnets could hold the secret to new quantum computers
Magnetic interactions could point to miniaturizable quantum devices. From MRI machines to computer hard disk storage, magnetism has played a role in pivotal discoveries that reshape our society. In the new field of quantum computing, magnetic interactions could play a role in relaying quantum information. In new research from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, scientists have achieved efficient quantum coupling between two distant magnetic devices, which can host a certain type of magnetic excitations called magnons. These excitations happen when an electric current generates a magnetic field. Coupling allows magnons to exchange energy and information. This kind of coupling may be useful for creating new quantum information technology devices. “Remote coupling of magnons is the first step, or almost a prerequisite, for doing quantum work with magnetic systems,” said Argonne senior scientist Valentine Novosad, an author of the study. “We show the ability for these magnons to communicate instantly with each other at a distance.” This instant communication does not require sending a message between magnons limited by the speed of light. It is analogous to what physicists call quantum entanglement. Following on from a 2019 study, the researchers sought to create a system that would allow magnetic excitations to talk to one another at a distance in a superconducting circuit. This would allow the magnons to potentially form the basis of a type of quantum computer. For the basic underpinnings of a viable quantum computer, researchers need the particles to be coupled and stay coupled for a long time. In order to achieve a strong coupling effect, researchers have built a superconducting circuit and used two small yttrium iron garnet (YIG) magnetic spheres embedded on the circuit. This material, which supports magnonic excitations, ensures efficient and low-loss coupling for the magnetic spheres. The two spheres are both magnetically coupled to a shared superconducting resonator in the circuit, which acts like a telephone line to create strong coupling between the two spheres even when they are almost a centimeter away from each other — 30 times the distance of their diameters. One additional improvement over the 2019 study involved the longer coherence of the magnons in the magnetic resonator. “Before, we definitely saw a relationship between magnons and a superconducting resonator, but in this study their coherence times are much longer because of the use of the spheres, which is why we can see evidence of separated magnons talking to each other,” Li added. According to Li, because the magnetic spins are highly concentrated in the device, the study could point to miniaturizable quantum devices. “It’s possible that tiny magnets could hold the secret to new quantum computers,” he said.
New material could lead to stronger, lighter and safer helmets and vehicles
A team of Johns Hopkins University researchers created shock-absorbing material that protects like a metal, but is lighter, stronger, reusable. The new foam-like material could be a game-changer for helmets, body armor, and automobile and aerospace parts. “We are excited about our findings on the extreme energy absorption capability of the new material,” said senior author Sung Hoon Kang, an assistant professor of mechanical engineering. “The material offers more protection from a wide range of impacts, but being lighter could reduce fuel consumption and the environmental impact of vehicles while being more comfortable for protective gear wearers.” Kang, who is also a fellow at the Hopkins Extreme Materials Institute, wanted to create a material even more energy-absorbing than current car bumpers and helmet padding. He noticed the typical materials used for these critical protective devices don’t perform well at higher speeds and often aren’t reusable. The research team was able to add strength while reducing weight with high energy-absorbing liquid crystal elastomers (LCEs), which have been used mainly in actuators and robotics. During experiments to test the material’s ability to withstand impact, it held up against strikes from objects weighting about four to 15 pounds, coming at speeds of up to about 22 miles per hour. The tests were limited to 22 miles per hour due to limits of the testing machines, but the team is confident the padding could safely absorb even greater impacts. Kang and his team are exploring a collaboration with a helmet company to design, fabricate, and test next-generation helmets for athletes and the military.
Nanostructure Combines Copper, Gold and Silver to Give Carbon Capture and Utilization a Boost
Chemists have developed a nano-scale structure that combines copper, gold, and silver to work as a superior catalyst in a chemical reaction whose improved performance will be essential if carbon capture and utilization efforts are to succeed in helping to mitigate global warming. In the face of the climate change challenge, in recent years, policy-makers have increasingly focused on carbon-capture-and-utilization (CCU), wherein CO2 is drawn down from the atmosphere and then used as a feedstock for industrial chemicals (such as carbon monoxide, formic acid, ethylene, and ethanol) or for the production of carbon-neutral synthetic fuels (especially useful for hard-to-electrify transport sectors such as long-haul aviation and shipping). So long as the latter process is powered by clean electricity, it also offers a way to store renewable energy over the long term—the holy grail of overcoming the intermittency of energy options such as wind and solar power. One possible means of doing all this is via a chemical reaction called the electrochemical CO2 reduction reaction (eCO2RR, or simply ECR). This uses electricity to power the conversion of the gas into other usable substances by separating CO2’s carbon atoms from its oxygen atoms. Water can also provide hydrogen “donors” in some varieties of ECR whereby the carbon atoms are combined with hydrogen to produce various species of hydrocarbons or alcohols. Key to ECR is using the right catalyst, or chemical substance whose structure and charge enables it to kick off or speed up a chemical reaction. Various different metals have been used as catalysts depending on which end product is desired. Catalysts employing just one type of metal include tin to produce formic acid, silver for carbon monoxide (CO), and copper for methane, ethylene or ethanol. However, the performance of the process can be limited when ECR competes with the tendency of hydrogen atoms within the electrochemical splitting of water to pair up with themselves instead of joining up with the carbon atoms. This competition can lead to production (or “selection”) of a different chemical end product than the one desired. As a result, chemists have long been on the hunt for catalysts with high “selectivity”. Recently, instead of just using a single metal as a catalyst, researchers have turned to the use of heterostructures that incorporate two distinct materials whose combined properties produce different or superior outcomes to either of the individual materials on their own. Some of the heterostructures that have been tested for ECR include combining silver and palladium in a branchlike formation (AgPd “nanodentrites”), and various other combinations of two metals in sandwich-like, tube-like, pyramidal and other shapes. Researchers have enjoyed considerable success with bimetallic heterostructures that include copper—which is very good at converting CO2 into products that use two carbon atoms. These bimetallic heterostructures include silver-copper (AgCu), zinc-copper (ZnCu), and gold-copper (AuCu), with the latter enjoying particular selectivity success for methane, C2 and carbon monoxide. So the researchers constructed a trimetallic nanostructure that combined gold, silver and copper and was asymmetric in form. The shape and precise ratio of the three metals can be altered via a growth method involving multiple steps. Specifically, gold “nanopyramids” are first synthesized and used as “seeds” for subsequent growth of various trimetallic structures involving different ratios of the three metals. They found as a result of the unique form of their heterostructure design and by altering the ratios of these three metals, they could carefully tune the selectivity toward different C2-based products. Production of ethanol (C2H6O) in particular was maximized by using a heterostructure with the feeding ratio involving one atom each of gold and silver combined with five copper atoms. The work sets out a promising strategy for development of other trimetallic nanomaterials within ECR development.
Things are heating up for superconductors
Researchers at Linköping University have, by way of a number of theoretical calculations, shown that magnesium diboride becomes superconductive at a higher temperature when it is stretched. The discovery is a big step toward finding superconductive materials that are useful in real-world situations. “Magnesiumdiboride or MgB2 is an interesting material. It’s a hard material that is used for instance in aircraft production and normally it becomes superconductive at a relatively high temperature, 39 K, or -234 C°,” says Erik Johansson, who recently completed his doctorate at the Division of Theoretical Physics. “Magnesium boride has an uncomplicated structure which means that the calculations on the supercomputers here at the National Supercomputer Centre in Linköping can focus on complex phenomena like superconductivity,” he says. Access to renewable energy is fundamental for a sustainable world, but even renewable energy disappears in the form of losses during transmission in the electrical networks. These losses are due to the fact that even materials that are good conductors have a certain resistance, resulting in losses in the form of heat. For this reason, scientists worldwide are trying to find materials that are superconductive, that is, that conduct electricity with no losses at all. Such materials exist, but superconductivity mostly arises very close to absolute 0, i.e. 0 K or -273,15 °C. Many years of research have resulted in complicated new materials with a maximum critical temperature of maybe 200 K, that is, -73 °C. At temperatures under the critical temperature, the materials become superconductive. Research has also shown that superconductivity can be achieved in certain metallic materials at extremely high pressure. If the scientists are successful in increasing the critical temperature, there will be greater opportunities to use the phenomenon of superconductivity in practical applications.
“The main goal is to find a material that is superconductive at normal pressure and room temperature. The beauty of our study is that we present a smart way of increasing the critical temperature without having to use massively high pressure, and without using complicated structures or sensitive materials. Magnesium diboride behaves in the opposite way to many other materials, where high pressure increases the ability to superconduct. Instead, here we can stretch the material by a few per cent and get a huge increase in the critical temperature,” says Erik Johansson. In the nanoscale, the atoms vibrate even in really hard and solid materials. In the scientists’ calculations of magnesium diboride, it emerges that when the material is stretched, the atoms are pulled away from each other and the frequency of the vibrations changes. This means that in this material, the critical temperature increases — in one case from 39 K to 77 K. If magnesium diboride is instead subjected to high pressure, its superconductivity decreases. The discovery of this phenomenon paves the way for calculations and tests of other similar materials or material combinations that can increase the critical temperature further. “One possibility could be to mix magnesium diboride with another metal diboride, creating a nanolabyrinth of stretched MgB2 with a high superconductive temperature,” says Björn Alling, docent and senior lecturer at the Division of Theoretical Physics and director of the National Supercomputer Centre at Linköping University.
Simply printing high-performance perovskite-based transistors
High-performance components in various smart devices have been successfully printed and have attracted much attention. And now, a technology to print perovskite-based devices — considered a challenge until now — has been proposed. A POSTECH research team led by Professor Yong-Young Noh and Ph.D. candidates Ao Liu and Huihui Zhu (Department of Chemical Engineering), in collaboration with Professor Myung-Gil Kim (School of Advanced Materials Science and Engineering) of Sungkyunkwan University, has improved the performance of a p-type semiconductor transistor using inorganic metal halide perovskite. One of the biggest advantages of the new technology is that it enables solution-processed perovskite transistors to be simply printed as semiconductor-like circuits. Perovskite-based transistors control the current by combining p-type semiconductors that exhibit hole mobilities with n-type semiconductors. Compared to n-type semiconductors that have been actively studied so far, fabricating high-performance p-type semiconductors has been a challenge. Many researchers have tried to utilize perovskite in the p-type semiconductor for its excellent electrical conductivity, but its poor electrical performance and reproducibility have hindered commercialization. To overcome this issue, the researchers used the modified inorganic metal halide caesium tin triiodide (CsSnI3) to develop the p-type perovskite semiconductor and fabricated the high-performance transistor based on this. This transistor exhibits high hole mobility of 50cm2V-1s-1 and higher and the current ratio of more than 108, and recorded the highest performance among the perovskite semiconductor transistors that have been developed so far. By making the material into a solution, the researchers succeeded in simply printing the p-type semiconductor transistor as if printing a document. This method is not only convenient but also cost-effective, which can lead to the commercialization of perovskite devices in the future. “The newly developed semiconductor material and transistor can be widely applicable as logic circuits in high-end displays and in wearable electronic devices, and also be used in stacked electronic circuits and optoelectronic devices by stacking them vertically with silicon semiconductors,” explained Professor Yong-Young Noh on the significance of the study.
Owl wing design reduces aircraft, wind turbine noise pollution
Trailing-edge noise is the dominant source of sound from aeronautical and turbine engines like those in airplanes, drones, and wind turbines. Suppressing this noise pollution is a major environmental goal for some urban areas. Researchers from Xi’an Jiaotong University used the characteristics of owl wings to inform airfoil design and significantly reduce the trailing-edge noise. “Nocturnal owls produce about 18 decibels less noise than other birds at similar flight speeds due to their unique wing configuration,” said author Xiaomin Liu. “Moreover, when the owl catches prey, the shape of the wings is also constantly changing, so the study of the wing edge configuration during owl flight is of great significance.” Trailing-edge noise is generated when airflow passes along the back of an airfoil. The flow forms a turbulent layer of air along the upper and lower surfaces of the airfoil, and when that layer of air flows back through the trailing edge, it scatters and radiates noise. Previous studies explored serrated trailing edges, finding that the serrations effectively reduce the noise of rotating machinery. However, the noise reduction was not universal, depending heavily on the final application. “At present, the blade design of rotating turbomachinery has gradually matured, but the noise reduction technology is still at a bottleneck,” said Liu. “The noise reduction capabilities of conventional sawtooth structures are limited, and some new non-smooth trailing-edge structures need to be proposed and developed to further tap the potential of bionic noise reduction.” The team used noise calculation and analysis software to conduct a series of detailed theoretical studies of simplified airfoils with characteristics reminiscent of owl wings. They applied their findings to suppress the noise of rotating machinery. Improving the flow conditions around the trailing edge and optimizing the shape of the edge suppressed the noise. Interestingly, asymmetric serrations reduced the noise more than their symmetric counterparts. Noise reduction varied with different operating conditions, so the scientists emphasized that the airfoil designs should be further evaluated based on the specific application. For example, wind turbines have complex incoming flow environments, which require a more general noise reduction technology. Examining noise reduction techniques under the influence of different incoming flows would make their conclusions more universal. The researchers believe their work will serve as an important guide for airfoil design and noise control.
Zentropy: New Theory of Entropy May Solve Materials Design Issues
Entropy is the measure of the disorder in a system that occurs over a period of time with no energy put into restoring the order. Zentropy integrates entropy at multiscale levels.
A challenge in materials design is that in both natural and manmade materials, volume sometimes decreases, or increases, with increasing temperature. While there are mechanical explanations for this phenomenon for some specific materials, a general understanding of why this sometimes happens remains lacking. However, a team of Penn State researchers has come up with a theory to explain and then predict it: Zentropy. Zentropy is a play on entropy, a concept central to the second law of thermodynamics that expresses the measure of the disorder of a system that occurs over a period of time when there is no energy applied to keep order in the system. Think of a playroom in a preschool; if no energy is put into keeping it tidy, it quickly becomes disordered with toys all over the floor, a state of high entropy. If energy is put in via cleaning up and organizing the room once the children leave, then the room returns to a state of order and low entropy. Zentropy theory notes that the thermodynamic relationship of thermal expansion, when the volume increases due to higher temperature, is equal to the negative derivative of entropy with respect to pressure, i.e., the entropy of most material systems decreases with an increase in pressure. This enables Zentropy theory to be able to predict the change of volume as a function of temperature at a multiscale level, meaning the different scales within a system. Every state of matter has its own entropy, and different parts of a system have their own entropy. The authors of the study, believe that Zentropy may be able to predict anomalies of other physical properties of phases beyond volume. This is because responses of a system to external stimuli are driven by entropy. Macroscopic functionalities of materials stem from assemblies of microscopic states (microstates) at all scales at and below the scale of the macroscopic state of investigation. These functionalities are challenging to predict because only one or a few microstates can be considered in a typical computational approach such as the predictive “from the beginning” calculations, which help determine the fundamental properties of materials. Zentropy theory “stacks” these different scales into an entropy theory that encompasses the different elements of an entire system, presenting a nested formula for the entropy of complex multiscale systems, according to Liu. This approach has been something Liu’s lab has worked on for more than 10 years and five different published studies. Zentropy has potential to change the way materials are designed, especially those that are part of systems that are exposed to higher temperatures. These temperatures, given thermal expansion, could cause issues if the materials expand. “This has the potential to enable the fundamental understanding and design of materials with emergent properties, such as new superconductors and new ferroelectric materials that could potentially lead to new classes of electronics,” Liu said. “Also, other applications such as designing better structural materials that withstand higher temperatures are also possible.” While there are benefits for society in general, researchers could apply Zentropy to multiple fields. This is because of how entropy is present in all systems. “The Zentropy theory has the potential to be applied to larger systems because entropy drives changes in all systems whether they are black holes, planets, societies or forests,” Liu said.
Ionic Liquids Make a Splash in Next-Generation Solid-State Lithium Metal Batteries
Quasi-solid-state-electrodes realize a significant reduction in interfacial resistance. Researchers from Tokyo Metropolitan University have developed a new quasi-solid-state cathode for solid-state lithium metal batteries, with significantly reduced interfacial resistance between the cathode and a solid electrolyte. By adding an ionic liquid, their modified cathode could maintain excellent contact with the electrolyte. Their prototype battery also showed good retention of capacity. Though finding the best ionic liquid remains challenging, the idea promises new directions in solid lithium battery development for practical applications. Lithium-ion batteries have become ubiquitous, finding a place in our smartphones, laptops, power tools, and electric vehicles. But as we look for better solutions with higher energy density, scientists have been turning to solid-state lithium metal batteries. Li metal batteries potentially have much higher energy density than their Li-ion counterparts. They are seen as the future of batteries, powering vehicles and grids on massive scales. However, technical issues keep solid-state lithium metal batteries from making their way into demanding applications. A major one is the design of the interface between electrodes and solid electrolytes. Electrolytes in Li-ion batteries are usually liquid and highly flammable, posing a safety hazard. That’s why people have been trying to use a solid-state electrolyte instead. However, it is difficult to achieve good contact between electrodes and solid electrolytes. Any surface roughness on either side leads to high interfacial resistance, which plagues battery performance. There has been some work looking at the design of the solid electrolyte, but cathode design remains an open issue. A team led by Prof. Kiyoshi Kanamura of Tokyo Metropolitan University have been developing new ways of improving the contact between the cathode and solid-state electrolyte in solid-state lithium metal batteries. Now, they have succeeded in creating a quasi-solid-state lithium cobalt oxide (LiCoO2) cathode which contains a room-temperature ionic liquid. Ionic liquids consist of positive and negative ions; they can also transport ions. Importantly, they can fill any tiny voids at the cathode/solid electrolyte interface. With the voids filled, the interfacial resistance was significantly decreased. The team’s method has other benefits too. Ionic liquids are not only ionically conductive but almost non-volatile and usually non-flammable. They also have minimal effect on the slurry from which the cathode is formed, leaving the manufacturing process virtually untouched. The team demonstrated a prototype battery made with their quasi-solid-state cathode and a solid “garnet” electrolyte (referring to its structure), which showed good rechargeability, with 80% capacity retention after 100 charge/discharge cycles at an elevated temperature of 60°C. Further study also revealed an optimal ionic liquid content of 11wt%. Issues remain, like finding a better ionic liquid that doesn’t degrade as easily. However, the team’s new paradigm promises exciting new directions for research into solid-state lithium metal batteries, with the potential to bring them out of the lab, and into our lives.
Breakthrough application of moisture-trapping film to reduce heat stress in personal protective suits
A team of researchers from the National University of Singapore (NUS) has developed a novel super-hygroscopic material that enhances sweat evaporation within a personal protective suit, to create a cooling effect for better thermal comfort for users such as healthcare workers and other frontline officers. The new desiccant film, which is biocompatible and non-toxic, has fast absorption rate, high absorption capacity and excellent mechanical properties. This means that the material is very robust and durable for practical applications such as for protective suits worn by healthcare workers. It is also affordable, light-weight, easy to fabricate and reusable. Attaching a piece of novel composite film in a protective suit — for example at the back of the suit — could bring down the heat index by about 40%, remarkably lowering the likelihood of heat stroke. This research breakthrough demonstrates the positive outcome of leveraging the complementary strengths of NUS and HTX to create tangible benefits for the Home Team and the wider community. By combining the NUS team’s scientific knowledge of advanced hydrogel materials and HTX’s deep understanding of the Home Team’s needs and engineering capabilities, the joint research team was able to customise and optimise the novel moisture-trapping material for practical applications to enhance the performance and productivity of frontline officers. Medical protective suits have excellent anti-bacterial and water-proof properties. However, this high level of protection stops the venting of water vapour produced by evaporated sweat and impedes heat loss from the body. This is why users such as healthcare workers who need to don protective suits for long hours, especially in tropical environments, often report of occupational heat strain. Thermal management solutions such as air-cooling garments with electrical fans or ingestion of ice slurry are impractical due to limitations such as bulkiness, heavy weight, and limited effectiveness. While advanced textiles and coatings are promising solutions, they are difficult to fabricate and production costs are high. The NUS team came up with a practical strategy to overcome the current challenges by leveraging the principle of evaporative cooling. Their solution involves using a super-hygroscopic composite film to control the humidity level in the micro-environment in the protective suit. When the moisture-trapping composite film absorbs water vapour within the protective suit, the humidity level drops. This in turn speeds up sweat evaporation from the skin. As a result, more heat is dissipated from the human body through sweating, providing thermal comfort for users such as healthcare workers. To examine the effectiveness of their solution, the NUS team conducted tests in collaboration with researchers from HTX, using a 20-zone ‘Newton’ manikin within a climatic chamber. This is an important experimental milestone in assessing the feasibility of applying the composite film to the scale of full body clothing. With the composite film, relative humidity (RH) under moderate sweating condition dropped by about 40% — from 91% to 48.2% after one hour of sweating and to 53.2% after two hours of sweating. The team also found that within the first hour of sweating, the heat index or ‘felt air temperature’ dropped significantly from 64.6 deg C to 40 deg C at air temperature of 35 deg C. At this level, while users still feel hot, the likelihood of getting heat stroke, heat cramps and heat exhaustion is remarkably reduced. In another laboratory experiment, the research team also showed that body temperature (or skin temperature) could be significantly reduced by 1.5 deg C through evaporative cooling. This further proves that the composite film can potentially help users — such as healthcare workers, soldiers or firefighters — relieve thermal stress, especially during strenuous activities. Regeneration of the NUS team’s composite film is also more energy efficient, as it requires a lower temperature to release the trapped moisture. At 50 deg C, the composite film releases 80% of its water contents after 10 minutes and this reaches 95% after 40 minutes. Most hygroscopic materials regenerate at a temperature of more than 100 deg C, over a duration of more than an hour. Encouraged by the results of their latest study, the NUS team is now working to improve their hygroscopic material so that it can absorb more and faster. The team is also planning to apply their cooling strategy to other types of protective apparel such as those for firefighters.