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Engineering

Breaking New Ground in Metasurfaces: A Bilayer Device that Tames Polarized Light

Researchers have created a bilayer metasurface made of two stacked layers of titanium dioxide nanostructures, opening new possibilities for structuring light.

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The world of optics has just taken a significant leap forward with the development of a bilayer metasurface by researchers at Harvard University’s John A. Paulson School of Engineering and Applied Sciences (SEAS). This breakthrough device, made up of two stacked layers of titanium dioxide nanostructures, represents a major innovation in the field of metasurfaces – ultra-thin, flat devices that can precisely control the behavior of light.

For centuries, optical systems have relied on bulky, curved lenses to bend and focus light. However, with the advent of metasurface technology, we now have flat, ultra-thin structures that can manipulate light with nanometer precision. These metalenses, for instance, can be fabricated using existing semiconductor manufacturing processes, making possible compact, integrated optical systems in devices like smartphones, cameras, and augmented reality displays.

The SEAS-led team, led by senior author Federico Capasso, has taken this technology to the next level by creating a bilayer metasurface. This device is made up of two stacked layers of titanium dioxide nanostructures that hold strongly together but do not affect each other chemically. While multi-level patterning is common in silicon semiconductors, it had not been as well explored in optics and metaoptics.

To demonstrate the power of their device, the team devised an experiment in which they used their bilayer metalens to act on polarized light in the same way that a complicated system of waveplates and mirrors does. This is a significant breakthrough, as previous metasurfaces had limitations when it came to manipulating light’s polarization.

The potential applications of this technology are vast. Imagine a system that projects one image from one side and a completely different image from the other. Such multifunctional optical devices could revolutionize fields like imaging systems, augmented reality, spectroscopy, and communications.

The research was supported by several federal funding sources, including the Office of Naval Research and the Air Force Office of Scientific Research. The devices were made at the Harvard University Center for Nanoscale Systems, part of the National Nanotechnology Coordinated Infrastructure Network, which is supported by the National Science Foundation.

This breakthrough has significant implications for the future of optics and metaoptics. With this bilayer metasurface technology, researchers can now expand into even more layers to exert control over other aspects of light, such as extreme broadband operation with high efficiency across the entire visible and near infrared spectrum. This could lead to even more sophisticated light-based functionalities in various fields.

The development of this bilayer metasurface is a testament to the ingenuity and creativity of researchers at Harvard University’s SEAS. It represents a significant step forward in the field of metasurfaces and has the potential to revolutionize the way we interact with light.

Batteries

“Revolutionizing Energy Storage: AI-Driven Discovery of New Materials for Multivalent-Ion Batteries”

AI is helping scientists crack the code on next-gen batteries that could replace lithium-ion tech. By discovering novel porous materials, researchers may have paved the way for more powerful and sustainable energy storage using abundant elements like magnesium.

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In a groundbreaking breakthrough, researchers from New Jersey Institute of Technology (NJIT) have successfully employed artificial intelligence to identify five powerful new materials that could potentially replace traditional lithium-ion batteries. These innovative discoveries were made possible through the application of generative AI techniques to rapidly explore thousands of material combinations.

Unlike conventional lithium-ion batteries, which rely on lithium ions carrying a single positive charge, multivalent-ion batteries use elements such as magnesium, calcium, aluminum, and zinc whose ions carry two or even three positive charges. This unique property allows multivalent-ion batteries to potentially store significantly more energy, making them highly attractive for future energy storage solutions.

However, the greater size and electrical charge of multivalent ions make it challenging to accommodate them efficiently in battery materials – a hurdle that the NJIT team’s new AI-driven research directly addresses. “One of the biggest hurdles wasn’t a lack of promising battery chemistries – it was the sheer impossibility of testing millions of material combinations,” said Professor Dibakar Datta, leading researcher on the project.

To overcome this obstacle, the NJIT team developed a novel dual-AI approach: a Crystal Diffusion Variational Autoencoder (CDVAE) and a finely tuned Large Language Model (LLM). These AI tools rapidly explored thousands of new crystal structures, something previously impossible using traditional laboratory experiments.

The CDVAE model was trained on vast datasets of known crystal structures, enabling it to propose completely novel materials with diverse structural possibilities. Meanwhile, the LLM was tuned to zero in on materials closest to thermodynamic stability, crucial for practical synthesis. “Our AI tools dramatically accelerated the discovery process, which uncovered five entirely new porous transition metal oxide structures that show remarkable promise,” said Datta.

The team validated their AI-generated structures using quantum mechanical simulations and stability tests, confirming that the materials could indeed be synthesized experimentally and hold great potential for real-world applications. Datta emphasized the broader implications of their AI-driven approach: “This is more than just discovering new battery materials – it’s about establishing a rapid, scalable method to explore any advanced materials, from electronics to clean energy solutions, without extensive trial and error.”

With these encouraging results, Datta and his colleagues plan to collaborate with experimental labs to synthesize and test their AI-designed materials, pushing the boundaries further towards commercially viable multivalent-ion batteries. This exciting breakthrough has the potential to revolutionize the field of energy storage, paving the way for a more sustainable future.

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Chemistry

Revolutionizing Magnetic Field Technology: A Breakthrough Design for MRI and Magnetic Levitation

Two German physicists have reimagined how to create powerful and uniform magnetic fields using compact permanent magnets. By overcoming the limitations of the well-known Halbach array, which works only with infinitely long magnets, they engineered innovative 3D magnet arrangements that work in practical, finite-size setups. Their designs not only boost field strength but also enhance homogeneity, verified through real-world experiments. This game-changing advancement could help bring affordable MRI technology to underserved regions and power applications like particle accelerators and magnetic levitation systems.

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Physicists at the University of Bayreuth and Johannes Gutenberg University Mainz have made a groundbreaking discovery that could transform the way we generate magnetic fields. Prof. Dr. Ingo Rehberg and Dr. Peter Blümler developed an innovative approach to create homogeneous magnetic fields using compact, permanent magnets. This breakthrough design outperforms the traditional Halbach arrangement, which is ideal only for infinitely long and therefore unrealizable magnets.

The new approach presents optimal three-dimensional arrangements of very compact magnets, idealized by point dipoles. The researchers investigated the optimal orientation of the magnets for two geometries relevant to practical use: a single ring and a stacked double ring. This “focused” design allows the generation of homogeneous fields outside the magnet plane, enabling applications such as magnetic levitation systems.

To validate their theoretical predictions, Rehberg and Blümler constructed magnet arrays from 16 FeNdB cuboids mounted on 3D-printed supports. The resulting magnetic fields were measured and compared with theoretical calculations, revealing excellent agreement. In terms of both magnetic field strength and homogeneity, the new configurations clearly outperform the classical Halbach arrangement.

The potential applications of this breakthrough design are vast. Conventional MRI technology relies on powerful superconducting magnets, which are technically complex and extremely costly. The new approach offers a promising alternative for generating homogeneous magnetic fields using permanent magnets. Additionally, this innovation could lead to advancements in particle accelerators and magnetic levitation systems.

This study was published in the renowned interdisciplinary journal Physical Review Applied, showcasing significant advances at the intersection of physics with engineering, materials science, chemistry, biology, and medicine. The implications of this breakthrough design are far-reaching, and further research is expected to uncover new possibilities for its applications.

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Batteries

Unlocking the Potential of Solid-State Batteries

Researchers have discovered that the mixing of small particles between two solid electrolytes can generate an effect called a ‘space charge layer,’ an accumulation of electric charge at the interface between the two materials. The finding could aid the development of batteries with solid electrolytes, called solid-state batteries, for applications including mobile devices and electric vehicles.

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The development of solid-state batteries has been gaining momentum in recent years, promising safer and more powerful alternatives to traditional lithium-ion batteries. A team of researchers from the University of Texas at Dallas has made a significant breakthrough in this field by discovering that mixing small particles between two solid electrolytes can generate an effect called a “space charge layer.” This accumulation of electric charge at the interface between the materials has been found to create pathways that make it easier for ions to move across, potentially leading to better-performing solid-state batteries.

The researchers, led by Dr. Laisuo Su and Dr. Kyeongjae Cho, published their study in ACS Energy Letters, where it was featured on the cover of the March issue. They discovered that when the separate solid electrolyte materials make physical contact, a layer forms at their boundary where charged particles, or ions, accumulate due to differences in each material’s chemical potential.

“Imagine mixing two ingredients in a recipe and unexpectedly getting a result that is better than either ingredient alone,” Dr. Su explained. “This effect boosted the movement of ions beyond what either material could achieve by itself.”

The research is part of the university’s Batteries and Energy to Advance Commercialization and National Security (BEACONS) initiative, which aims to develop and commercialize new battery technology and manufacturing processes. The team’s findings suggest a new way to design better solid electrolytes by carefully choosing materials that interact in a way that enhances ionic movement.

Solid-state batteries show promise for generating and storing more than twice as much power as batteries with liquid electrolytes, while being safer because they are not flammable. However, the development of solid-state batteries faces challenges due to difficulties in moving ions through solid materials.

The researchers plan to continue studying how the composition and structure of the interface lead to greater ionic conductivity. This breakthrough has the potential to unlock the full potential of solid-state batteries, enabling advanced battery systems that can improve the performance of drones for defense applications.

In conclusion, the discovery of the space charge layer phenomenon offers a promising new direction for the development of solid-state batteries. By understanding and harnessing this effect, researchers may be able to create more efficient and powerful batteries that meet the growing demands of mobile devices, electric vehicles, and other applications.

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