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Category: materials – Page 35

Twisted crystals open door to smaller, more powerful sensors for optical devices

Twisted moiré photonic crystals—an advanced type of optical metamaterial—have shown enormous potential in the race to engineer smaller, more capable and more powerful optical systems. How do they work?

Imagine you have two pieces of fabric with regular patterns, like stripes or checkers. When you lay the two pieces of fabric directly on top of each other, you can see each pattern clearly. But if you slightly shift one piece of fabric or twist it, new patterns that weren’t in either of the original fabrics emerge.

In twisted moiré photonic crystals, how the layers twist and overlap can change how the material interacts with light. By changing the twist angle and the spacing between layers, these materials can be fine-tuned to control and manipulate different aspects of light simultaneously—meaning the multiple optical components typically needed to simultaneously measure light’s phase, polarization, and wavelength could be replaced with one device.

Researchers Disprove Their Own Work by Producing Power From Earth’s Rotation

A trio of US researchers claim to have successfully tested predictions that it’s possible to harvest clean energy from the natural rhythms and processes of our planet, generating electricity as Earth rotates through its own magnetic field.

Though the voltage they produced was tiny, the possibility could give rise to a new way to generate electricity from our planet’s dynamics, alongside tidal, solar, wind, and geothermal power production.

In 2016, Princeton astrophysicist Christopher Chyba and JPL planetary scientist Kevin Hand challenged their own proof that such a feat ought to be impossible. The researchers have now uncovered empirical evidence that their proof-breaking idea may actually work, as long as the shape and properties of the conducting material in their method are set to very specific requirements.

A 32-bit RISC-V processor made using molybdenum disulfide instead of silicon

A team of engineers at Fudan University has successfully designed, built and run a 32-bit RISC-V microprocessor that uses molybdenum disulfide instead of silicon as its semiconductor component. Their paper is published in the journal Nature.

Most microprocessors are made using the semiconductor silicon, which has worked out well for several decades. But as researchers attempt to make processors ever smaller, they have run into a dead end with silicon—they cannot make it any thinner. Instead, many researchers have turned to 2D materials such as graphene, but this is challenging because it is a conductor, not a semiconductor.

In this new study, the research team used a nearly 2D semiconducting material, single-molecule sheets of molybdenum disulfide. These sheets are not truly 2D because they bond at an angle, resulting in a slightly zigzag surface. To make a processor out of them, they put them on a sapphire substrate.

With affordable materials, researchers pull carbon directly from the air using changes in humidity

Researchers at Northwestern University have expanded the potential of carbon capture technology that plucks CO2 directly from the air by demonstrating that there are multiple suitable and abundant materials that can facilitate direct air capture.

In a paper titled “Platform materials for moisture-swing carbon capture” published in the journal Environmental Science & Technology, the researchers present new, lower-cost materials to facilitate moisture-swing to catch and then release CO2 depending on the local air’s moisture content, calling it “one of the most promising approaches for CO2 capture.”

Atmospheric CO2 continues to increase and, despite considerable worldwide efforts to cut down on carbon waste, is expected to rise more in coming decades.

A new wave in ultrafast magnetic control

Researchers at the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have developed an innovative method to study ultrafast magnetism in materials. They have shown the generation and application of magnetic field steps, in which a magnetic field is turned on in a matter of picoseconds.

The work has been published in Nature Photonics.

Magnetic fields are fundamental to controlling the magnetization of materials. Under static or slowly varying conditions, a material’s magnetization aligns with the external field like a compass needle. However, entirely new magnetization dynamics emerge when magnetic fields change on timescales—faster than the material’s response time.

Enhancing light control with complex frequency excitations

Researchers at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) and at Florida International University report in the journal Science their insights on the emerging field of complex frequency excitations, a recently introduced scheme to control light, sound and other wave phenomena beyond conventional limits.

Based on this approach, they outline opportunities that advance fundamental understanding of wave-matter interactions and usher wave-based technologies into a new era.

In conventional light-wave-and sound-wave-based systems such as wireless cell phone technologies, microscopes, speakers and earphones, control over wave phenomena is limited by constraints, which stem from the fundamental properties of the materials used in these technologies.

Supersonic speed limit for strong metal bonding revealed

Faster isn’t always better when it comes to high-speed materials science, according to new Cornell research showing that tiny metal particles bond best at a precise supersonic speed.

In industrial processes like cold spray coating and , tiny metal particles travel at extreme speeds and slam into a surface with such force that they fuse together, forming strong metallic bonds. This rapid, high-energy collision builds up layers of material, creating durable, high-performance components. Understanding how and why these bonds form, and sometimes fail, can help optimize manufacturing techniques and lead to stronger materials.

In a study published March 31 in the Proceedings of the National Academy of Sciences, Cornell scientists launched , each about 20 micrometers in diameter, onto an aluminum surface at speeds of up to 1,337 meters per second—well beyond the speed of sound—and used high-speed cameras to record the impacts.

Highly twisted metamaterial rods store large amounts of energy

An international research team coordinated at KIT (Karlsruhe Institute of Technology) has developed mechanical metamaterials with a high elastic energy density. Highly twisted rods that deform helically provide these metamaterials with a high stiffness and enable them to absorb and release large amounts of elastic energy. The researchers conducted simple compression experiments to confirm the initial theoretical results. Their findings have been published in the journal Nature.

Storage of mechanical energy is required for many technologies, including springs for absorbing energy, buffers for mechanical energy storage, or flexible structures in robotics or energy-efficient machines. Kinetic energy, i.e., motion energy or the corresponding mechanical work, is converted into elastic energy in such a way that it can be fully released again when required.

The key characteristic here is enthalpy—the energy density that can be stored in and recovered from an element of the material. Peter Gumbsch, Professor for at KIT’s Institute for Applied Materials (IAM), explains that achieving the highest possible enthalpy is challenging: “The difficulty is to combine conflicting properties: high stiffness, and large recoverable strain.”

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