Moiré systems incorporating lead iodide can host exotic quantum states and enable near-lossless electrical transport.
Category: materials
A monster black hole appeared first, then its galaxy began to grow around it
Using observations gathered by the James Webb Space Telescope (JWST), an international team of astronomers have revealed that one supermassive black hole in the early universe must have formed before a galaxy developed around it. Publishing their results in Monthly Notices of the Royal Astronomical Society, a team led by Roberto Maiolino at the University of Cambridge hope their results could lead to a better understanding of the origins of these immense objects.
Supermassive black holes (SMBH) are known to lurk at the centers of most galaxies, including our own Milky Way. Carrying up to billions of times the mass of the sun, they have presented a long-standing conundrum to astronomers.
According to our latest models, black holes form from the remnants of supernova explosions, which most often occur when massive stars reach the ends of their lives. Afterwards, they can grow by consuming gas from surrounding accretion disks—but their growth rate is restricted by a brightness threshold called the “Eddington limit.” Beyond this point, the outward pressure from radiation exceeds the gravitational pull, and material is ejected into space.
A stretchy, heat-activated skin patch could be a surgery-free melanoma treatment
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Melanoma is a deadly form of skin cancer that is typically removed surgically. Now, researchers publishing in ACS Nano report they have developed a potential noninvasive treatment for melanoma in the form of a stretchy, heat-activated patch similar to a bandage. When activated, the patch releases copper ions that kill the underlying cancer cells and prevent them from spreading. In tests with mice, the researchers say the patch reduced melanoma lesions without damaging surrounding tissue.
Flexible batteries kept stable with stretchy metallic films
Stretchable films filled with liquid metal can protect flexible electronic devices from exposure to air and water. The finding could offer a potential way to improve the lifetime of future forms of wearable technology.
Most stretchable materials are highly permeable to gases. This makes it challenging to fully protect flexible electronic devices from things like air and moisture, which can ruin their performance.
Now researchers in China and the US have developed stretchable seals based on liquid metals that block the transport of oxygen and water. The seals are formed of a eutectic gallium indium alloy, which is laminated between two layers of silicone-based polymer.
3D-printing electronics with focused microwaves redefines possibilities in materials
In a recently published paper in Science Advances, a team led by Rice University’s Yong Lin Kong describes a new 3D-printing process with focused microwaves that overcomes a fundamental constraint of electronics 3D printing that has limited the field’s potential for more than a decade: the inability to heat printed ink—a crucial processing step—without damaging the materials underneath.
The ability to integrate functional materials and spatially program their properties governs both device performance and the limits of what can be built. Existing manufacturing approaches are fundamentally limited in both respects. Electronic components, for instance, are fabricated in massive, centralized foundries, often decoupled from the final device. Integrating them requires complex, labor-intensive assembly that constrains both the form and the function of what can ultimately be created.
Multimaterial 3D printing should, in principle, allow fabrication of free-form architectures in which electronic and mechanical properties are programmed directly into the structure. However, the thermal processing required to render printed electronic inks functional destroys the very materials these devices require.
‘Ghost tunnels’ guide sound waves in one direction while staying invisible to others
Acoustic metamaterials are a fast-evolving family of materials which manipulate sound waves in ever more advanced ways. Now, a team led by Changqing Xu at Nanjing Normal University in China has engineered an acoustic metamaterial, a “ghost tunnel”: a structure which acts as a near-perfect waveguide for sound entering through its ends, while being essentially invisible to waves incident on its sides. The results, published in Physical Review Letters, could open new avenues for manipulating sound waves in complex signal environments.
Acoustic waveguides work by confining sound within a channel, using boundaries that reflect waves back inward to keep them on track. While this can be achieved with a structure as simple as a hollow pipe, the problem is that those same reflective boundaries inevitably interact with any sound waves approaching from outside the channel.
Rather than passing through undisturbed, external waves scatter off the rigid walls: a significant drawback in technologies where multiple signal channels must coexist in close proximity without interfering with one another.
Scientists May Have Found the Key to Jupiter and Saturn’s Moon Mystery
Jupiter and Saturn, the two largest planets in our Solar System, also host the most extensive systems of moons. Jupiter is currently known to have more than 100 moons, while Saturn, along with its prominent ring system, has more than 280.
Despite these large numbers, their moon systems are very different. Jupiter has four major moons, including Ganymede, the largest moon in the Solar System. Saturn, on the other hand, is dominated by a single standout moon, Titan, which ranks as the second largest.
Because both planets are gas giants, scientists have long tried to understand why their satellite systems developed so differently. Existing theories of moon formation offer some explanations, but recent research on stellar magnetic fields suggests those ideas may need revision. One key question involves magnetic accretion and whether an inner cavity can form in Jupiter’s circumplanetary disk, the accumulation of material orbiting a planet from which satellites may form.
A Macroscopic Magnet Precesses
An isolated magnet’s intrinsic angular momentum induces gyroscopic motion, an observation that could lead to ultrasensitive magnetometers.
In 1861, physicist James Clerk Maxwell proposed that a magnet behaves to some extent like a spinning gyroscope [1], but his experiments never managed to demonstrate the effect. Since then, researchers have observed various manifestations of so-called gyromagnetism, mostly in specialized magnetic materials or with spinning magnets, but now a research team has detected signatures of gyroscopic motion corresponding to Maxwell’s original ideas [2]. The team used a microscopic magnetic sphere in a technique that, with improvements, could be employed for ultrasensitive magnetic-field detection, which could be useful for research on biological magnetism.
If you try to tilt a gyroscope spinning around a vertical axis, it will respond by tilting at 90° from the push direction, an effect that leads to precession in response to gravity—such as the slow loop executed by the axis of a spinning top. An electron in a magnetic field behaves like a gyroscope in a gravitational field because the electron has a magnetic moment, which is associated with intrinsic angular momentum, or spin. So you might expect that a material whose microscopic spins align—such as an ordinary ferromagnet—would have a macroscopic angular momentum and behave like a gyroscope.
Underwater architects: Nest-building in cichlids reveals more than hardwired instinct
We associate nests with shelter, warmth, and a safe retreat—and usually picture a bird’s nest made out of twigs, grass and feathers. Yet many other animals take advantage of such refuges, with nests being built by a diversity of species ranging from termites to great apes, which impress with their hugely varied forms and the wide array of materials used to construct them.
For fish, nest-building comes with an added challenge as they must put together their underwater nests equipped with “only” their fins. Yet fish too have developed a remarkable variety of nest-building innovations, burrowing into sandy lake beds, creating masses of floating bubbles on the water’s surface, or setting up camp in abandoned snail shells repurposed as nests—as is the case with the shell-dwelling cichlid Lamprologus ocellatus.
Endemic to Lake Tanganyika in Africa, these cichlids use empty snail shells for shelter and to raise their young. To do so, the snail shell is positioned and covered in sand in a very specific way, leaving just the opening exposed—only then does it become the perfect home.