Category: Chemistry

Researchers from the University of Toronto’s Faculty of Applied Science & Engineering and Fujitsu have developed a new way of searching through ‘chemical space’ for materials with desirable properties.

The technique has resulted in a promising new catalyst material that could help lower the cost of producing clean hydrogen.

The discovery represents an important step toward more sustainable ways of storing energy, including from renewable but intermittent sources, such as solar and wind power.

“Scaling up the production of what we call green hydrogen is a priority for researchers around the world because it offers a carbon-free way to store electricity from any source,” says Ted Sargent, a professor in the Edward S. Rogers Sr. department of electrical and computer engineering and senior author on a new paper published in Matter.

“This work provides proof-of-concept for a new approach to overcoming one of the key remaining challenges, which is the lack of highly active catalyst materials to speed up the critical reactions.”

Today, nearly all commercial hydrogen is produced from natural gas. The process produces carbon dioxide as a byproduct: if the CO₂ is vented to the atmosphere, the product is known as ‘grey hydrogen,’ but if the CO₂ is captured and stored, it is called ‘blue hydrogen.’

By contrast, ‘green hydrogen’ is a carbon-free method that uses a device known as an electrolyzer to split water into hydrogen and oxygen gas. The hydrogen can later be burned or reacted in a fuel cell to regenerate the electricity. However, the low efficiency of available electrolyzers means that most of the energy in the water-splitting step is wasted as heat, rather than being captured in the hydrogen.

Researchers around the world are racing to find better catalyst materials that can improve this efficiency. But because each potential catalyst material can be made of several different chemical elements, combined in a variety of ways, the number of possible permutations quickly becomes overwhelming.

“One way to do it is by human intuition, by researching what materials other groups have made and trying something similar, but that’s pretty slow,” says department of materials science and engineering Ph.D. candidate Jehad Abed, one of two co-lead authors on the new paper.

“Another way is to use a computer model to simulate the chemical properties of all the potential materials we might try, starting from first principles. But in this case, the calculations get really complex, and the computational power needed to run the model becomes enormous.”

To find a way through, the team turned to the emerging field of quantum-inspired computing. They made use of the Digital Annealer, a tool that was created as the result of a long-standing collaboration between U of T Engineering and Fujitsu Research. This collaboration has also resulted in the creation of the Fujitsu Co-Creation Research Laboratory at the University of Toronto.

“The Digital Annealer is a hybrid of unique hardware and software designed to be highly efficient at solving combinatorial optimization problems,” says Hidetoshi Matsumura, senior researcher at Fujitsu Consulting (Canada) Inc.

“These problems include finding the most efficient route between multiple locations across a transportation network, or selecting a set of stocks to make up a balanced portfolio. Searching through different combinations of chemical elements to a find a catalyst with desired properties is another example, and it was a perfect challenge for our Digital Annealer to address.”

In the paper, the researchers used a technique called cluster expansion to analyze a truly enormous number of potential catalyst material designs—they estimate the total as a number on the order of hundreds of quadrillions. For perspective, one quadrillion is approximately the number of seconds that would pass by in 32 million years.

The results pointed toward a promising family of materials composed of ruthenium, chromium, manganese, antimony and oxygen, which had not been previously explored by other research groups.

The team synthesized several of these compounds and found that the best of them demonstrated a mass activity— a measure of the number of reactions that can be catalyzed per mass of the catalyst—that was approximately eight times higher than some of the best catalysts currently available.

The new catalyst has other advantages too: it operates well in acidic conditions, which is a requirement of state-of-the-art electrolyzer designs. Currently, these electrolyzers depend on catalysts made largely of iridium, which is a rare element that is costly to obtain. In comparison, ruthenium, the main component of the new catalyst, is more abundant and has a lower market price.

There is more work ahead for the team: for example, they aim to further optimize the stability of the new catalyst before it can be tested in an electrolyzer. Still, the latest work serves as a demonstration of the effectiveness of the new approach to searching chemical space.

“I think what’s exciting about this project is that it shows how you can solve really complex and important problems by combining expertise from different fields,” says electrical and computer engineering Ph.D. candidate Hitarth Choubisa, the other co-lead author of the paper.

“For a long time, materials scientists have been looking for these more efficient catalysts, and computational scientists have been designing more efficient algorithms, but the two efforts have been disconnected. When we brought them together, we were able to find a promising solution very quickly. I think there are a lot more useful discoveries to be made this way.”

More information: Hitarth Choubisa et al, Accelerated chemical space search using a quantum-inspired cluster expansion approach, Matter (2022). DOI: 10.1016/j.matt.2022.11.031

Journal information: Matter 

Provided by University of Toronto 

A University of Kent team, led by Professors Ben Goult and Jen Hiscock, has created and patented a new shock-absorbing material that could revolutionize both the defense and planetary science sectors.

This novel protein-based family of materials, named TSAM (Talin Shock Absorbing Materials), represents the first known example of a SynBio (or synthetic biology) material capable of absorbing supersonic projectile impacts. This opens the door for the development of next-generation bulletproof armor and projectile capture materials to enable the study of hypervelocity impacts in space and the upper atmosphere (astrophysics).

Professor Ben Goult explained, “Our work on the protein talin, which is the cell’s natural shock absorber, has shown that this molecule contains a series of binary switch domains which open under tension and refold again once tension drops. This response to force gives talin its molecular shock absorbing properties, protecting our cells from the effects of large force changes. When we polymerized talin into a TSAM, we found the shock absorbing properties of talin monomers imparted the material with incredible properties.”

The team went on to demonstrate the real-world application of TSAMs, subjecting this hydrogel material to 1.5 km/s supersonic impacts—a faster velocity than particles in space impact both natural and man-made objects (typically > 1 km/s) and muzzle velocities from firearms—which commonly fall between 0.4–1.0 km/s. Furthermore, the team discovered that TSAMs can not only absorb the impact of basalt particles (~60 µM in diameter) and larger pieces of aluminum shrapnel, but also preserve these projectiles post-impact.

Current body armor tends to consist of a ceramic face backed by a fiber-reinforced composite, which is heavy and cumbersome. Also, while this armor is effective in blocking bullets and shrapnel, it doesn’t block the kinetic energy which can result in behind armor blunt trauma.

Furthermore, this form of armor is often irreversibly damaged after impact, because of compromised structural integrity preventing further use. This makes the incorporation of TSAMs into new armor designs a potential alternative to these traditional technologies, providing a lighter, longer-lasting armor that also protects the wearer against a wider range of injuries including those caused by shock.

In addition, the ability of TSAMs to both capture and preserve projectiles post-impact makes it applicable within the aerospace sector, where there is a need for energy dissipating materials to enable the effective collection of space debris, space dust and micrometeoroids for further scientific study.

Furthermore, these captured projectiles facilitate aerospace equipment design, improving the safety of astronauts and the longevity of costly aerospace equipment. Here TSAMs could provide an alternative to industry standard aerogels—which are liable to melt due to temperature elevation resulting from projectile impact.

Professor Jen Hiscock said, “This project arose from an interdisciplinary collaboration between fundamental biology, chemistry and materials science which has resulted in the production of this amazing new class of materials. We are very excited about the potential translational possibilities of TSAMs to solve real world problems. This is something that we are actively undertaking research into with the support of new collaborators within the defense and aerospace sectors.”

The work is published on the bioRxiv preprint server.

More information: Jack A. Doolan et al, Next generation protein-based materials capture and preserve projectiles from supersonic impacts, bioRxiv (2022). DOI: 10.1101/2022.11.29.518433

Provided by University of Kent 

Researchers of the University of Amsterdam, together with colleagues at the University of Queensland and the Norwegian Institute for Water Research, have developed a strategy using machine learning to assess the toxicity of chemicals.

They present their approach in an article in Environmental Science & Technology for the special issue “Data Science for Advancing Environmental Science, Engineering, and Technology.” The models developed in this study can lead to substantial improvements when compared to conventional “in silico” assessments based on Quantitative Structure-Activity Relationship (QSAR) modeling.

According to the researchers, the use of machine learning can vastly improve the hazard assessment of molecules, both in the safe-by-design development of new chemicals and in the evaluation of existing chemicals. The importance of the latter is illustrated by the fact that European and U.S. chemical agencies have listed approximately 800,000 chemicals that have been developed over the years but for which there is little to no knowledge about environmental fate or toxicity.

Since an experimental assessment of chemical fate and toxicity requires much time, effort, and resources, modeling approaches are already used to predict hazard indicators. In particular the Quantitative Structure-Activity Relationship (QSAR) modeling is often applied, relating molecular features such as atomic arrangement and 3D structure to physicochemical properties and biological activity.

Based on the modeling results (or measured data where available), experts classify a molecule into categories as defined for example in the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). For specific categories, molecules are then subjected to more research, more active monitoring and eventually legislation.

However, this process has inherent drawbacks, much of which can be traced back to the limitations of the QSAR models. They are often based on very homogeneous training sets and assume a linear structure-activity relationship for making extrapolations. As a result, many chemicals are not well-represented by existing QSAR models and their uses can potentially lead to substantial prediction errors and misclassification of chemicals.

Skipping the QSAR prediction

In their paper published in Environmental Science & Technology, Dr. Saer Samanipour and co-authors propose an alternative evaluation strategy that skips the QSAR prediction step altogether.

Samanipour, an environmental analytical scientist at the University of Amsterdam’s Van ‘t Hoff Institute for Molecular Sciences teamed up with Dr. Antonia Praetorius, an environmental chemist at the Institute for Biodiversity and Ecosystem Dynamics of the same university. Together with colleagues at the University of Queensland and the Norwegian Institute for Water Research, they developed a machine learning-based strategy for the direct classification of acute aquatic toxicity of chemicals based on molecular descriptors.

The model was developed and tested via 907 experimentally obtained data for acute fish toxicity (96h LC50 values). The new model skips the explicit prediction of a toxicity value (96h LC50) for each chemical, but directly classifies each chemical into a number of pre-defined toxicity categories.

These categories can for example be defined by specific regulations or standardization systems, as demonstrated in the article with the GHS categories for acute aquatic hazard. The model explained around 90% of the variance in the data used in the training set and around 80% for the test set data.

Higher accuracy predictions

This direct classification strategy resulted in a fivefold decrease in the incorrect categorization compared to a strategy based on a QSAR regression model. Subsequently, the researchers expanded their strategy to predict the toxicity categories of a large set of 32,000 chemicals.

They demonstrate that their direct classification approach results in higher accuracy predictions because experimental datasets from different sources and for different chemical families can be grouped to generate larger training sets. It can be adapted to different predefined categories as prescribed by various international regulations and classification or labeling systems.

In the future, the direct classification approach can also be expanded to other hazard categories (e.g. chronic toxicity) as well as to environmental fate (e.g. mobility or persistence) and shows great potential for improving in-silico tools for chemical hazard and risk assessment.

More information: Saer Samanipour et al, From Molecular Descriptors to Intrinsic Fish Toxicity of Chemicals: An Alternative Approach to Chemical Prioritization, Environmental Science & Technology (2022). DOI: 10.1021/acs.est.2c07353

Journal information: Environmental Science & Technology 

Provided by University of Amsterdam 

A team of researchers at Zhejiang University School of Medicine has developed a way to use photosynthetic cells from plants when treating osteoarthritis in mice.

In their paper published in the journal Nature, the group describes how they created nanoscale thylakoid structures, called nanothylakoid units, in plants and delivered them into animal cells as a way to slow or stop disease progression. Two of the team members, Pengfei Chen and Xianfeng Lin have also published a Research Briefing outlining their work in the same journal issue.

Prior research has shown that in some progressive diseases, such as osteoarthritis, cells lack the amount of energy they need to function properly due to insufficient anabolism (where simple molecules are converted to complex molecules). Prior research has also shown that the compound ATP provides the energy needed by mammalian cells.

Prior research has also shown that the molecule NADPH plays an important role in allowing cells to use ATP. And finally, prior research has also shown that both ATP and NADHP are produced in plants during photosynthesis. The researchers therefore wondered if it might be possible to deliver some of the plant machinery into a mammalian cell where it could be used to produce ATP and NADPH for use by the mammalian cells when a light was applied, instigating the photosynthetic process.

To find out, the researchers created structures called nanothylakoid units (NTUs) from plant chloroplasts. They then covered them with mouse cells to prevent the mouse immune system from attacking when the NTUs were injected into the knee joints of mice with osteoarthritis.

Next, they shined a light on the joints to incite the photosynthetic process and thus the production of ATP and NADPH. Testing showed that the technique led to improved anabolism in the mouse cells, which in turn led to reducing the progression of the disease (slowed cartilage degeneration) in the test mice.

The researchers suggest their initial experiments show that their approach holds promise as a therapeutic approach to treating progressive diseases. They also note that the same approach could be used to metabolize cells as part of a process to create biofuels and perhaps other useful chemicals.

More information: Pengfei Chen et al, A plant-derived natural photosynthetic system for improving cell anabolism, Nature (2022). DOI: 10.1038/s41586-022-05499-y

Plant-cell machinery for making metabolites transferred to mammalian cells, Nature (2022). DOI: 10.1038/d41586-022-03629-0

Journal information: Nature 

© 2022 Science X Network

Cholesterol is an essential component of the membrane surrounding every human cell, despite its poor reputation as a health concern when its blood levels are too high. The key to health is having the right amount of cholesterol in the right places. Maintaining appropriate levels is known as cholesterol homeostasis.

Researchers at the Institute for Integrated Cell-Material Science (iCeMS) at Kyoto University in Japan have gained new insights into how cells achieve cholesterol homeostasis within the cell membrane. The findings are published in the Journal of Biological Chemistry.

Cholesterol molecules are packed inside the cell membrane at levels that control membrane fluidity, thickness and flexibility. These characteristics are vital for making the membrane a selective semi-permeable barrier, with crucial control over what substances can travel into and out of cells.

“Disturbances in cholesterol homeostasis can lead to some serious diseases, but it has been unclear how cells detect and respond to changes in cholesterol levels in the cell membrane,” says iCeMS cellular biochemist Kazumitsu Ueda.

Ueda and his colleague Fumihiko Ogasawara have now revealed a vital role of two proteins in maintaining an appropriate distribution of cholesterol inside cells and their membranes.

The first protein, called ATP-binding cassette A1 (ABCA1) translocates cholesterol within the membrane. The cell membrane is composed of a lipid bilayer, with inner and outer layers of fatty molecules (phospholipids, cholesterol, and glycolipids) oriented in opposite directions.

A key new insight reported in this current study is that the ABCA1 protein controls the transfer of cholesterol molecules from the inner layer to the outer layer. The researchers call this process “cholesterol flopping.” Their previous work explored this protein’s role in facilitating cholesterol transfer through the bloodstream in the form of high-density lipoprotein (HDL), sometimes called good cholesterol.

Ueda and Ogasawara also uncovered details of how a second protein—cholesterol transfer protein Aster-A—acts cooperatively with ABCA1 to maintain the crucial asymmetric distribution of cholesterol, with more cholesterol in the outer layer of the cell membrane than the inner. Aster-A is located inside the cell embedded in the endoplasmic reticulum. When there is an increase in the cholesterol level in the inner layer of the cell membrane, Aster-A forms a bridge transferring cholesterol from the cell membrane to the endoplasmic reticulum.

The researchers describe how the asymmetric distribution of cholesterol in the membrane allows it to serve a signaling function, influencing other cellular processes in ways that depend on the degree of asymmetry. They suggest that this explains why defects in the normal functioning of ABCA1 can cause faulty molecular signaling that may lead to cancer and autoimmune diseases.

“The progress we have made needs to be built on to better understand all the implications of these cholesterol homeostasis processes in both health and disease,” Ueda concludes. He hopes this may eventually open new avenues to treating diseases linked to cholesterol imbalance.

More information: Fumihiko Ogasawara et al, ABCA1 and cholesterol transfer protein Aster-A promote an asymmetric cholesterol distribution in the plasma membrane, Journal of Biological Chemistry (2022). DOI: 10.1016/j.jbc.2022.102702

Journal information: Journal of Biological Chemistry 

Provided by Kyoto University 

The biochemical process by which cyanobacteria acquire nutrients from rocks in Chile’s Atacama Desert has inspired engineers at the University of California, Irvine to think of new ways microbes might help humans build colonies on the moon and Mars.

Researchers in UCI’s Department of Materials Science and Engineering and Johns Hopkins University’s Department of Biology used high-resolution electron microscopy and advanced spectroscopic imaging techniques to gain a precise understanding of how microorganisms modify both naturally occurring minerals and synthetically made nanoceramics. A key factor, according to the scientists, is that cyanobacteria produce biofilms that dissolve magnetic iron oxide particles within gypsum rocks, subsequently transforming the magnetite into oxidized hematite.

The team’s findings, which are the subject of a paper published recently in the journal Materials Today Bio, could provide a pathway for new biomimetic mining methods. The authors also said they see the results as a step toward using microorganisms in large-scale 3D printing or additive manufacturing at a scale that’s useful in civil engineering in harsh environments, like those on the moon and Mars.

“Through a biological process that has evolved over millions of years, these tiny miners excavate rocks, extracting the minerals that are essential to the physiological functions, such as photosynthesis, that enable their survival,” said corresponding author David Kisailus, UCI professor of materials science and engineering. “Could humans use a similar biochemical approach to obtain and manipulate the minerals that we find valuable? This project has led us down that pathway.”

The Atacama Desert is one of the driest and most inhospitable places on Earth, but Chroococcidiopsis, a cyanobacterium found in gypsum samples collected there by the Johns Hopkins team, has developed “the most amazing adaptations to survive its rocky habitat,” said co-author Jocelyne DiRuggiero, associate professor of biology at the Baltimore university.

“Some of those traits include producing chlorophyll that absorbs far-red photons and the ability to extract water and iron from surrounding minerals,” she added.

Using advanced electron microscopes and spectroscopic instruments, the researchers found evidence of the microbes in the gypsum by observing how the very minerals contained within were transformed.

“Cyanobacteria cells promoted magnetite dissolution and iron solubilization by producing abundant extracellular polymeric substances, leading to the dissolution and oxidation of magnetite to hematite,” DiRuggiero said. “Production of siderophores [iron-binding compounds generated by bacteria and fungi] was enhanced in the presence of magnetite nanoparticles, suggesting their use by the cyanobacteria to acquire iron from magnetite.”

Kisailus said the way the microorganisms process metals in their desolate home made him think about our own mining and manufacturing practices.

“When we mine for minerals, we often wind up with ores that may present challenges for extraction of valuable metals,” he said. “We frequently need to put these ores through extreme processing to transform it into something of value. That practice can be monetarily and environmentally costly.”

Kisailus said he is now pondering a biochemical approach using natural or synthetic analogs to siderophores, enzymes and other secretions to manipulate minerals where only a large mechanical crusher currently works. And taking a leap from here, he said there could also be a way to get microorganisms to employ similar biochemical capabilities to produce an engineered material on demand in less-than-convenient locations.

“I call it ‘lunar forming’ instead of terraforming,” Kisailus said. “If you want to build something on the moon, instead of going through the expense of having people do it, we could have robotic systems 3D-print media and then have the microbes reconfigure it into something of value. This could be done without endangering human lives.”

He added that humans don’t always need to use Edisonian approaches to figure out how to do things.

“This is the main theme of my Biomimetics and Nanostructured Materials Lab. Why try to reinvent the wheel when nature’s perfected it over hundreds of millions of years?” Kisailus said. “We just have to extract the secrets and blueprints for what nature does and apply or adapt them to what we need.”

More information: Wei Huang et al, Iron acquisition and mineral transformation by cyanobacteria living in extreme environments, Materials Today Bio (2022). DOI: 10.1016/j.mtbio.2022.100493

Provided by University of California, Irvine 

In a recent paper in Nature Communications, researchers at the Industrial Sustainable Chemistry group led by Prof. Gert-Jan Gruter take an important step towards the production of fully bio-based, rigid polyesters.

They present a simple, yet innovative, synthesis strategy to overcome the inherently low reactivity of bio-based secondary diols and arrive at polyesters that have very good mechanical- and thermal properties, and at the same time high molecular weights. It enables the production of very strong and durable bio-based plastics from building blocks that are already commercially available.

The research described in the Nature Communications paper was carried out within the RIBIPOL project funded by the Dutch Research Council NWO with contributions from industry, notably LEGO and Avantium. The toy company supported the project as part of the search for non-fossil alternatives for its plastic bricks. Avantium is interested in bottle- and film applications. First author of the paper is Ph.D. student Daniel Weinland, who graduated on October 27. In total, five Ph.D. students are involved in the RIBIPOL project, of which two have defended their thesis recently.

Rigidity is key

In general, polyester plastics are synthesized from small dialcohol and diacid molecules. These monomers are coupled in a condensation reaction, resulting in a long polymer chain of molecular building blocks in an alternating fashion. The macroscopic material properties result both from the number of building blocks that make up the polymer chain, and from the inherent properties of the monomers.

In particular their rigidity is key to a firm, strong and durable plastic. In this regard, the glucose-derived dialcohol isosorbide is unique among potential bio-based monomers. It has a very rigid molecular structure and is already industrially available.

However, isosorbide is rather unreactive, and in the past two decades it has proven quite challenging to obtain useful isosorbide-based polyesters. It was nearly impossible to arrive at sufficiently long polymer chains (to achieve a certain ductility) while incorporating sufficiently high amounts of isosorbide (to arrive at a strong and durable material).

Incorporating an aryl alcohol

Weinland and his RIBIPOL colleagues have overcome this impasse by incorporating an aryl alcohol in the polymerization process. This leads to in situ formation of reactive aryl esters and a significant enhancement of the end group reactivity during polycondensation, the last stage of polyester synthesis when isosorbides low reactivity inhibits chain growth in traditional melt polyesterification. As a result, high molecular weight materials could be produced with incorporation of high fractions of the bio-based, rigid secondary diol, even up to 100 mol%.

For the first time, high molecular weight poly(isosorbide succinate) could be produced, the polyester obtained from isosorbide and succinic acid. The resulting strong plastics outperform existing plastics like PET in terms of heat resistance, which is for instance relevant for re-use—think of washing bottles that takes place at 85 °C. The isosorbide-based polymers also show promising barrier and mechanical properties that can outperform common fossil-based materials.

The novel polymerization approach described in the paper is characterized by operational simplicity and the use of standard polyester synthesis equipment. It suits both existing and novel polyester compositions; the researchers foresee exploration of previously inaccessible polyester compositions based on monomers with a low reactivity but also the application of similar methods in other classes of polymers such as polyamides and polycarbonates.

More information: Daniel H. Weinland et al, Overcoming the low reactivity of biobased, secondary diols in polyester synthesis, Nature Communications (2022). DOI: 10.1038/s41467-022-34840-2

Journal information: Nature Communications 

Provided by University of Amsterdam 

A team of University of Illinois Urbana-Champaign Material Science and Engineering researchers have solved a long-standing puzzle about lower measured thermal conductivity values of cubic silicon carbide (3C-SiC) bulk crystals in the literature than the structurally more complex hexagonal phase SiC polytype (6H-SiC). The new measured thermal conductivity of bulk 3C-SiC has the second highest thermal conductivity among inch-scale large crystals, second only to diamond.

Professor David Cahill (Grainger Distinguished Chair in Engineering and co-director of the IBM-Illinois Discovery Accelerator Institute) and Dr. Zhe Cheng (Postdoc) report an isotropic high thermal conductivity of 3C-SiC crystals that exceeds 500 W m^-1K^-1. The team collaborated with Air Water, Inc, based in Japan, to grow high-quality crystals, with the thermal conductivity measurements performed at UIUC in the MRL Laser and Spectroscopy suite. Their results were recently published in Nature Communications.

Silicon carbide (SiC) is a wide bandgap semiconductor used commonly in electronic applications and has various crystalline forms (polytypes). In power electronics, a significant challenge is thermal management of high localized heat flux that can lead to overheating of devices and the degradation of device performance and reliability in the long-term. Materials with high thermal conductivity (κ) are critical in thermal management design.

Hexagonal phase SiC polytypes (6H and 4H) are the most widely used and extensively studied, whereas the cubic phase SiC polytype (3C) is less understood, despite it having the potential to have the best electronic properties and higher κ. Cahill and Zhe explain that there has been a long-standing puzzle about the measured thermal conductivity of 3C-SiC in the literature: 3C-SiC is lower than that of the structurally more complex 6H-SiC phase and measures lower than the theoretically predicted κ value.

This is a contradiction of predicted theory that structural complexity and thermal conductivity are inversely related (as structural complexity goes up, thermal conductivity should go down).

Zhe says that 3C-SiC is “not a new material, but the issue researchers have had before is poor crystal quality and purity, causing them to measure lower thermal conductivity than other phases of silicon carbide.” Boron impurities contained in the 3C-SiC crystals cause exceptionally strong resonant phonon scattering, which significantly lowers its thermal conductivity.

Wafer-scale 3C-SiC bulk crystals produced by Air Water Inc. were grown by low-temperature chemical vapor deposition and had high crystal quality and purity. The team observed high thermal conductivity from the high purity and high crystal quality 3C-SiC crystals.

Zhe says that “the measured thermal conductivity of 3C-SiC bulk crystals in this work is ~50% higher than the structurally more complex 6H-SiC, consistent with predictions that structural complexity and thermal conductivity are inversely related. Moreover, the 3C-SiC thin films grown on Si substrates have record-high in-plane and cross-plane thermal conductivities, even higher than that of diamond thin films with equivalent thicknesses.”

The high thermal conductivity measured in this work ranks 3C-SiC second to single crystal diamond among inch-scale crystals, which has the highest κ among all natural materials. However, for thermal management materials, diamond is limited by its high cost, small wafer size, and difficulty in integration with other semiconductors.

3C-SiC is cheaper than diamond, can easily be integrated with other materials, and can be grown to large wafer sizes, making it a suitable thermal management material or an excellent electronic material with a high thermal conductivity for scalable manufacturing.

Cahill says, “The unique combination of thermal, electrical, and structural properties of 3C-SiC can revolutionize the next generation of electronics by using it as active components (electronic materials) or thermal management materials,” since 3C-SiC has the highest thermal conductivity among all SiC polytypes and helps facilitate device cooling and reduce power consumption.

The high thermal conductivity of 3C-SiC has potential to impact applications such as power electronics, radio-frequency electronics, and optoelectronics.

More information: Zhe Cheng et al, High thermal conductivity in wafer-scale cubic silicon carbide crystals, Nature Communications (2022). DOI: 10.1038/s41467-022-34943-w

Journal information: Nature Communications 

Provided by University of Illinois Grainger College of Engineering 

Researchers led by Prof. Chen Tao at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in cooperation with researchers at Ningbo University, have developed a novel breakage-resistant conductive hydrogel (BRC hydrogel) with excellent mechanical reliability, extending the service life of triboelectric nanogenerators (TENGs). This study was published in the Chemical Engineering Journal.

Benefitting from the facile fabrication, multiple structures, stable output and high energy conversion efficiency, TENGs have provided effective energy supply for the continuous operation of the Internet of Things (loT) system. Among them, hydrogel-based TENGs (H-TENGs) shows great advantages in the field of flexible wearable devices and self-powered applications. However, the poor mechanical properties of hydrogel electrode lead to a low mechanical reliability during the long-term operation, thus shortening the service life of H-TENGs.

Based on the Hofmeister effect on starch polymers, the researchers developed a facile and efficient solvent-exchange strategy to prepare BRC hydrogels with ultrahigh mechanical reliability. The formation of the bundling starch chains endows the BRC hydrogel with excellent modulus of ~0.87 MPa, fracture energy of 7.45 kJ/m², anti-puncture capacity of ~15 Mpa and long-term stability.

In addition, the electrical properties for the BRC hydrogel have improved remarkably, since abundant free ions (i.e. Na⁺, Cit^–) were introduced into the BRC hydrogel.

Employing this BRC hydrogel as electrode material, the researchers fabricated the BRC hydrogel based TENG (BRCH-TENG) with excellent electrical output performances and mechanical safety. The stable mechanical property under continuous physical impact contributes to improving the long-term stability of the BRCH-TENG, thus prolonging its service life upon accidental physical impact.

Furthermore, the fabricated BRCH-TENG shows bright and broad application prospects in the field of walking energy harvesting, real-time motion stride detection and information communication.

More information: Rui Li et al, Breakage-resistant hydrogel electrode enables ultrahigh mechanical reliability for triboelectric nanogenerators, Chemical Engineering Journal (2022). DOI: 10.1016/j.cej.2022.140261

Provided by Chinese Academy of Sciences