ACES...

FILE PHOTO: Dr. Benjamin Tee, Assistant Professor of Materials Science and Engineering at the National University of Singapore (NUS), demonstrates how his device can detect the texture of a soft stress ball at a lab in NUS, Singapore July 27, 2020. REUTERS/Joseph Campbell

Topics: Bioengineering, Materials Science, Star Wars, Robotics

The device, dubbed ACES, or Asynchronous Coded Electronic Skin, is made up of 100 small sensors and is about 1 sq cm (0.16 square inch) in size.

The researchers at the National University of Singapore say it can process information faster than the human nervous system, is able to recognize 20 to 30 different textures and can read Braille letters with more than 90% accuracy.

“So humans need to slide to feel the texture, but in this case, the skin, with just a single touch, is able to detect textures of different roughness,” said research team leader Benjamin Tee, adding that AI algorithms let the device learn quickly.

A demonstration showed the device could detect that a squishy stress ball was soft, and determine that a solid plastic ball was hard.

Scientists inspired by 'Star Wars' create artificial skin able to feel, Joseph Campbell, Reuters Science

Quantum Phase Battery...

The first quantum phase battery, consisting of an indium arsenide (InAs) nanowire in contact with aluminium superconducting leads. (Courtesy: Andrea Iorio)

Topics: Battery, Cooper Pairs, Materials Science, Quantum Mechanics, Superconductivity

Researchers in Spain and Italy have constructed the first-ever quantum phase battery – a device that maintains a phase difference between two points in a superconducting circuit. The battery, which consists of an indium arsenide (InAs) nanowire in contact with aluminium (Al) superconducting leads, could be used in quantum computing circuits. It might also find applications in magnetometry and highly sensitive detectors based on superconductors.

In a classical battery (also known as the Volta pile), chemical energy is converted into a voltage difference. The resulting current flow can then be used to power electronic circuits. In quantum circuits and devices based on superconducting materials, however, current may flow without an applied external voltage, thus dispensing with the need for a classical battery.

The concept of a quantum phase battery was studied theoretically in 2015 by Sebastián Bergeret of the Material Physics Center (CFM-CSIC) and Ilya Tokatly at the University of the Basque Country in Donostia-San Sebastián, Spain. Their battery design comprised a combination of superconducting and magnetic materials and was based on a Josephson junction – a non-superconducting region through which the Cooper pairs responsible for superconductivity can tunnel. This semiconducting “weak link” provides a persistent phase difference between the superconductors in the circuit, similar to the way that a classical battery provides a persistent voltage drop in an electronic circuit. Thanks to this phase difference, a superconducting current (that is, a current with zero dissipation) flows when the junction is embedded in the superconducting circuit.

Physicists create quantum phase battery, Isabelle Dumé, Physics World

Armored Surfaces...

A schematic representation of how the surface looks, and how the structure repels water. Courtesy: Aalto University

Topics: Materials Science, Nanotechnology, Surface Engineering

A micron-scale “armor” that protects highly water-repellent nanostructures from damage has been developed by researchers in China and Finland. The new extra-durable coating could make it possible to employ these “superhydrophobic” surfaces on devices such as solar panels and vehicle windscreens that experience tough environmental conditions.

As their name suggests, superhydrophobic materials repel water extremely well. They owe this impressive ability to a thin layer of air that develops around nanometre-scale structures on their surface. By ensuring that droplets barely touch the solid part of the surface at all, the air layer effectively acts as a lubricant, allowing water droplets to roll off with near-zero friction.

These nanostructured surfaces are, however, mechanically fragile and can easily be wiped away. To address this drawback, a research team led by Xu Deng of the University of Electronic Science and Technology of China in Chengdu and Robin Ras of Finland’s Aalto University created a superhydrophobic surface containing structures at two different length scales: a nanoscale structure that is water repellent and a microscale one that provides durability.

The microstructure consists of an interconnected frame containing “pockets” of tiny inverted pyramids. Within these pyramids are the highly water-repellent and mechanically fragile nanostructures. The frame thus acts as a shield, preventing the nanostructure coating from being removed by abradants larger than the frame. “A finger, screwdriver or even sandpaper glides over these microstructures, leaving the nanostructures untouched, thereby preserving the surface’s attractive water-repellent feature,” Ras says.

Superhydrophobic surfaces toughen up, Isabelle Dumé, Physics World

2D Boost for 5G...

A diagram of the UT Austin team's switch showing two gold electrodes with a layer of hBN in between. (Courtesy: UT Austin)

Topics:  Boron Nitride, Internet of Things, Materials Science, Nanotechnology

Two-dimensional sheets of boron nitride can be used to create an analogue switch that gives communication devices more efficient access to radio, 5G and terahertz frequencies while increasing their battery life. The switch, which was developed by a team of researchers at the University of Texas at Austin in the US and the University of Lille in France, could be employed in a host of different applications, including smartphones, mobile systems and the “Internet of things”.

Analogue switches are routinely employed in communication systems to switch from one frequency band to another, route signals between transmitting and receiving antennas, and reconfigure wireless networks. Traditionally, these switches are based on solid-state diodes or transistors, but components of this type consume energy even in standby mode, reducing the battery life of the device. With 5G networking set to drive a tenfold increase in data throughput – enabling advances in self-driving cars, delivery drones, remote surgery and fast downloads of high-definition media in the process – addressing this energy drain is more urgent than ever.

5G switching gets a 2D boost, Isabelle Dumé, Physics World

Photonic Nanojets...

FIG. 1. (a) Long-legs cellar spider. (b) Reeling mechanism. (c) Manufacturing process of decorating spider silk. (d) Spider silk with dome lens placed on a dedicated holder. (e) Microphotograph of dome lens. (f) Laser scanning digital microscope system for measuring dome lens. (g) Schematic diagram of the dome lens for generating PNJ.

Topics: Biology, Materials Science, Nanotechnology

ABSTRACT

In this work, we thoroughly investigate the shape, size, and location of the photonic nanojets (PNJs) generated from the illuminated dome lens. The silk fiber is directly extracted from the cellar spider and used to form the dome lens by its liquid-collecting ability. The solidified dielectric dome lenses with different dimensions are obtained by using ultraviolet curing. Numerical and experimental results show that the long PNJs are strongly modulated by the dimension of the dome lens. The optimal PNJ beam shaping is achieved by using a mesoscale dielectric dome lens. The PNJ with a long focal length and a narrow waist could be used to scan over a target for large-area imaging. The silk fiber with a dome lens is especially useful for bio-photonic applications by combining its biocompatibility and flexibility.

Optimal photonic nanojet beam shaping by mesoscale dielectric dome lens

Journal of Applied Physics 127, 243110 (2020); https://doi.org/10.1063/5.0007611

C.B. Lin, Yi-Ting Lee, and Cheng-Yang Liu

Kondo Effect...

Daniel Mazzone led the project to explore the mechanism that causes samarium sulphide to expand dramatically when cooled. Credit: Brookhaven National Laboratory

Topics: Materials Science, Quantum Mechanics, Research, Thermodynamics

Most metals expand when heated and contract when cooled. A few metals, however, do the opposite, exhibiting what’s known as negative thermal expansion (NTE). A team of researchers led by Ignace Jarrige and Daniel Mazzone of Brookhaven National Laboratory in the US has now found that in one such metal, yttrium-doped samarium sulphide (SmS), NTE is linked to a quantum many-body phenomenon called the Kondo effect. The work could make it possible to develop alloys in which positive and negative expansion cancel each other out, producing a composite material with a net-zero thermal expansion – a highly desirable trait for applications in aerospace and other areas of hi-tech manufacturing.

Even within the family of NTE materials, yttrium-doped SmS is an outlier, gradually expanding by up to 3% when cooled over a few hundred degrees. To better understand the mechanisms behind this “giant” NTE behavior, Mazzone and Jarrige employed X-ray diffraction and spectroscopy to investigate the material’s electronic properties.

The researchers carried out the first experiments at the Pair Distribution Function (PDF) beamline at Brookhaven’s National Synchrotron Light Source (II) (NSLS-II). They placed their SmS sample inside a liquid-helium cooled cryostat in the beam of the synchrotron X-rays and measured how the X-rays scattered off the electron clouds around the atomic ions. By tracking how these X-rays scatter, they identified the locations of the atoms in the crystal structure and the spacings between them.

“Our results show that, as the temperature drops, the atoms of this material move farther apart, causing the entire material to expand by up to 3% in volume,” says Milinda Abeykoon, the lead scientist on the PDF beamline.

Kondo effect induces giant negative thermal expansion, Belle Dumé, Physics World

Batteries, Diamonds and Nanothreads...

Next big thing:
Haifei Zhan and colleagues reckon that carbon nanothreads have a future in energy storage.
(Courtesy: Queensland University of Technology)
Topics: Applied Physics, Battery, Materials Science, Nanotechnology
Computational and theoretical studies of diamond-like carbon nanothreads suggest that they could provide an alternative to batteries by storing energy in a strained mechanical system. The team behind the research says that nanothread devices could power electronics and help with the shift towards renewable sources of energy.
The traditional go-to device for energy storage is the electrochemical battery, which predates even the widespread use of electricity. Despite centuries of technological progress and near ubiquitous use, batteries remain prone to the same inefficiencies and hazards as any device based on chemical reactions – sluggish reactions in the cold, the danger of explosion in the heat and the risk of toxic chemical leakages.

Another way of storing energy is to strain a material that then releases energy as it returns to its unstrained state. The strain could be linear like stretching and then launching a rubber band from your finger; or twisted, like a wind-up clock or toy. Over a decade ago, theoretical work done by researchers at the Massachusetts Institute of Technology suggested that strained chords made from carbon nanotubes could achieve impressive energy-storage densities, on account of the material’s unique  mechanical properties.

Diamond nanothreads could beat batteries for energy storage, theoretical study suggests
Anna Demmings, Physics World

Interphase...

Intro to Nano Energy: Lecture 5

Topics: Battery, Materials Science, Nanotechnology

What happens in a lithium-ion battery when it first starts running? A complex series of events, it turns out – from electrolytic ion reorganization to a riot of chemical reactions. To explore this early part of a battery’s life, researchers in the US have monitored a battery’s chemical evolution at the electrode surface. Their work could lead to improved battery design by targeting the early stages of device operation.

The solid-electrolyte interphase is the solid gunk that materializes around the anode. Borne from the decomposition of the electrolyte, it is crucial for preventing further electrolyte degradation by blocking electrons while allowing lithium ions to pass through to complete the electrical circuit.

The solid-electrolyte interphase does not appear immediately. When a lithium ion battery first charges up, the anode repels anions and attracts positive lithium ions, separating oppositely charged ions into two distinct layers. This electric double layer dictates the eventual composition and structure of the solid-electrolyte interphase.

Emergence of crucial interphase in lithium-ion batteries is observed by researchers
Shi En Kim, Physics World

Nonvolatile Charge Memory...

Light irradiation-controlled nonvolatile charge memory. Left: schematic of the memory device. Right: the optical-controlled writing and erasing process of source-drain current. (Courtesy: Q Li et al J. Phys. D: Appl. Phys. 10.1088/1361-6463/ab5737)

Topics: Applied Physics, Device Physics, Electrical Engineering, Materials Science, Nanotechnology

Qinliang Li, Cailei Yuan and Ting Yu from Jiangxi Normal University, along with Qisheng Wang and Jingbo Li from South China Normal University, are developing nonvolatile charge memory devices with simple structures. Wang explains how the optically controllable devices combine the functions of light sensing and electrical storage.

The research is reported in full in Journal of Physics D: Applied Physics, published by IOP Publishing – which also publishes Physics World.

What was the motivation for the research and what problem were you trying to solve?

Nonvolatile memory devices are central to modern communication and information technology. Among various material systems, emerging two dimensional (2D) materials offer a promising platform for next-generation data-storage devices due to their unique planar structure and brilliant electronic properties. However, 2D materials-based nonvolatile memory devices have complicated architectures with multilayer stacking of 2D materials, metals, organics or oxides. This limits the capacity for device miniaturization, scalability and integration functionality.

In this work, we are trying to design a nonvolatile charge memory with simple device architecture. We also expect to explore a new type of optical control on the charge storage devices, which may bring us smart operation on data deposition and communication.

Nonvolatile charge memory device shows excellent room-temperature performance, Physics World
Qisheng Wang is professor at the Institute of Semiconductor Science and Technology, South China Normal University

2D MXenes...

Helper two-dimensional metal-carbide layers could improve perovskite solar cell stability and help make these complex solar cells a viable green energy option. Credit: iStock Milos-Muller

Topics: Condensed Matter Physics, Green Tech, Materials Science, Metamaterials, Nanotechnology, Solar Power

With the reality of climate change looming, the importance of realistic green energy sources is higher than ever. Solar cells are one promising avenue, as they can convert readily available visible and ultraviolet energy into usable electricity. In particular, perovskite materials sandwiched between other support layers have demonstrated impressive power conversion efficiencies. Current challenges reside in optimizing perovskite/support layer interfaces, which can directly impact power conversion and cell degradation. Researchers Antonio Agresti et al. under the direction of Aldo Di Carlo at the University of Rome Tor Vergata in Italy have investigated how cells containing two-dimensional titanium-carbide MXene support layers could improve perovskite solar cell performance.

To obtain good power conversion within a perovskite solar cell, all layers and layer interfaces within the cell must have good compatibility. Typical cells contain the active perovskite material sandwiched between two charge transport layers, which are then adjacent to their corresponding electrodes. Support layers may also be added. Charge mobility, energy barriers, interface energy alignment, and interfacial vacancies all impact compatibility and subsequent cell performance and stability. Thus, engineering well-suited interfaces with the cell is paramount to cell success and long-term stability, an important criterion for potential commercialization.

Two-dimensional buffer materials could help to modify and promote useful interface interactions. MXenes, a growing class of two-dimensional transitional metal carbides, nitrides, and carbonitrides, have shown impressive electronic properties that are easily tuned via surface modification. For example, the band gap of an MXene can be modified by changing the surface termination group from an oxygen atom to a hydroxide molecule. Additionally, MXene composition impacts the overall material performance. This type of fine-tuning allows impressive control over MXene properties and makes them ideal for interface adjustments.

Two-dimensional MXenes improve perovskite solar cell efficiency
Amanda Carr, Physics World

#P4TC: MXenes...August 24, 2015

Boiling Superconductivity...

Under pressure: calculated structure of lithium magnesium hydride. Lithium atoms appear in green, magnesium in blue and hydrogen in red. (Courtesy: Ying Sun et al/Phys. Rev. Lett.)

Topics: Chemistry, Materials Science, Nanotechnology, Superconductors

A material that remains a superconductor when heated to the boiling point of water has been predicted by physicists in China. Hanyu Liu, Yanming Ma and colleagues at Jilin University have calculated that lithium magnesium hydride will superconduct at temperatures as high as 473 K (200 °C).

The catch is that the hydrogen-rich material must be crushed at 250 GPa, which is on par with pressures at the center of the Earth. While such a pressure could be achieved in the lab, it would be very difficult to perform an experiment to verify the prediction. The team’s research could, however, lead to the discovery of more practical high-temperature superconductors.

Superconductors are materials that, when cooled below a critical temperature, will conduct electricity with zero resistance. Most superconductors need to be chilled to very low temperatures, so the holy grail of superconductivity research is to find a substance that will superconduct at room temperature. This would result in lossless electricity transmission and boost technologies that rely on the generation or detection of magnetic fields.

Superconductivity at the boiling temperature of water is possible, say physicists
Hamish Johnston, Physics World

Room Tc...

The cage-like crystal structure (LaH₁₀) thought to be responsible for the high-temperature superconductivity observed in this study. Courtesy: R Hemley

Topics: Green Energy, Materials Science, Quantum Mechanics, Superconductors

Note: Room temperature is 300 K, which is 26.85 Celsius, 80.33 Fahrenheit.

A team of researchers from George Washington University in the US is saying that a hydride of lanthanum compressed to 200 GPa (2 Mbars) could be superconducting at temperatures near room temperature – a result that has been backed up with findings from another group in Germany. The results could be a major step towards realizing the long-sought goal of room-temperature superconductivity for energy applications.

Superconductivity is the ability of a material to conduct electricity without any resistance. It is observed in many materials when they are cooled to below their superconducting transition temperature (T_c). In the Bardeen-Cooper-Schrieffer (BCS) theory of (“conventional”) superconductivity, this occurs when electrons overcome their mutual electrical repulsion and form “Cooper pairs” that then travel unheeded through the material as a supercurrent.

Superconductivity was first observed in 1911 in solid mercury below a T_c of 4.2K (--268.95 Celsius, --452.11 Fahrenheit) and the search for room-temperature superconductors has been on ever since. Room-temperature superconductivity would help considerably improve the efficiency of electrical generators and transmission lines, as well simplify current applications of superconductivity, such as superconducting magnets in particle accelerators.

Researchers came a step closer to this holy grail with the high-temperature superconducting copper oxides, which were discovered in the 1990s and which have a Tc above liquid helium temperatures. It was only in 2015, however, that they discovered that hydrogen sulphide has a Tc of 203 K when compressed to pressures of 150 GPa. This result spurred a flurry of interest in the compressed hydrides – that is, solid materials containing hydrogen atoms bonded to other elements.

Dramatic resistance drop at 260 K

“We believe that a T_c at – or very near – room temperature has finally been realized,” says Russell Hemley, who led this latest research effort.

Thanks to quantum-mechanics-based calculations, Hemley’s group first predicted that lanthanum hydride (LaH₁₀) could be superconducting in July 2017. The researchers then synthesized the material, and reported direct measurements of its conductivity that indicated a T_c of 260 K (-13.15 Celsius, 8.33 Fahrenheit) at 180-200 GPa in May 2018, posting a paper on the arXiv in August 2018 that has now been published in Physical Review Letters. A team led by Mikhail Eremets at the Max Planck Institute for Chemistry in Germany reported on a T_c of 250 K (-23.15 Celsius, -9.67 Fahrenheit) for lanthanum hydride synthesized at pressures of around 170 GPa in independent work posted on the arXiv in December 2018.

Quantum-mechanics-based calculations for “materials by design”

The researchers say they have reproduced their result many times and also have preliminary magnetic susceptibility data that point to room-temperature superconductivity. To unequivocally prove, however, that this is indeed the case will require them to observe the Meissner effect (the expulsion of magnetic field from a material when it becomes superconducting) in LaH₁₀. This is challenging, they admit, but preliminary results from experiments on their samples at the Argonne National Laboratory in Illinoisare encouraging. Further work is also needed to characterize the superconducting properties of structures other than LaH₁₀ in their samples that they have predicted and observed using X-ray diffraction.

On the road to room-temperature superconductivity, Belle Dumé, Physics World

3D Topological Insulators...

Courtesy: H. Chen

Topics: Laser, Optical Physics, Photonics, Materials Science, Nanotechnology, Quantum Mechanics

Reference: Topological Insulators, then the rest of the post.

Researchers in China and Singapore say they have made the first ever 3D photonic topological insulator using a stack of thin plastic sheets embedded with metal nanoantennas. The insulator works at microwave frequencies, but if extended to terahertz or optical wavelengths, it could find use in applications such as high-power lasers, optical diodes and photonic computer chips.

2D topological insulators, also known as 2D quantum spin Hall insulators, are materials that are electrical insulators in the bulk but can conduct electricity extremely well on their edge via special, topologically protected, electronic states. Electrons can only travel in one direction along these states and do not backscatter. This means that they can carry electrical current with near-zero dissipation of energy and so could be used to make energy-efficient electronic devices in the future.

Structures made from photonic crystals

In recent years, researchers have started looking at making topological insulators that work using light rather than electric currents. These structures are made from photonic crystals – materials in which the periodic variation of the refractive index means that only certain wavelengths of light are able to pass through. One of the advantages of these photonic topological insulators is that they can operate at room temperature, unlike their electronic counterparts.

Another is that the space through which photons can travel can be engineered so that it is curved like the surface of a cone. These structures thus mimic a 2D quantum spin Hall insulator that naturally contains so-called surface Dirac cones. These are the sharp single points in a 2D material at which the valence and the conduction bands meet at the Fermi level, and at which electrons behave as though they are relativistic particles with no rest mass.

3D topological insulators go photonic, Belle Dumé, Physics World

Sudoku and Velocity Fields...

Image Source: Link below

Topics: Materials Science, Probability, Radiation, X-rays

To see what happens inside a pile of sand or another volume of granular material, researchers rely either on deformation observations at the surface, which don’t always reflect any internal flows, or on simulations. Several existing techniques can image interior flows, but they each have one or more disadvantages, such as limited spatial and temporal resolutions, high costs, and invasiveness. A new technique, developed by James Baker, Itai Einav, and their colleagues at the University of Sydney, overcame those hurdles by using sets of two-dimensional x-ray radiographs to uncover the three-dimensional velocity field inside a volume of opaque grains.

X rays were fired from three orthogonal locations through a container of opaque grains that were being sheared from below by a conveyor belt, as shown in the diagram above. By spatially correlating successive radiographs, the researchers extracted the probability density functions (PDFs) of the two displacement components orthogonal to the x-ray direction for each grid cell. Each PDF was then sampled evenly to generate an unsorted array of the different displacements through the beam direction.

By combining the PDF results orthogonal to each other and solving a Sudoku-style puzzle, the researchers were able to reconstruct the 3D velocity field shown from 2D projections. As in Sudoku, the displacement values that should be placed in each row and column are known from the two sets of PDFs, but how to arrange those displacements in space defines the puzzle. Unlike in Sudoku, though, there is no unique solution.

X-ray correlations assemble a complete velocity field, Alex Lopatka, Physics Today

Conjuring Ray Palmer...

MIT engineers have devised a way to create 3D nanoscale objects by patterning a larger structure with a laser and then shrinking it. This image shows a complex structure prior to shrinking. Courtesy: Daniel Oran

Topics: 3D Printing, Materials Science, Metamaterials, Nanotechnology, Science Fiction

A new 3D nanofabrication technique called Implosion Fabrication could be used to create a wide variety of nano- and microstructures not previously possible. The technique, which can print 3D objects of nearly any shape by patterning a polymer scaffold with a laser and then shrinking the structure to a thousandth of its original volume, might be used to make novel optical metamaterials and electronics devices.

Shrinking hydrogel scaffold

Most existing nanofabrication techniques are limited in what they can produce. Direct laser writing methods, for example, can produce 2D patterns but not 3D ones, which need to be built up a layer at a time – a process that is difficult and slow. Lithography, one of the oldest nanofabrication techniques, can again only print 2D layers on patterned surfaces.

The apropos cultural reference that absolutely dates me!

Image Source: Wikipedia link below

Raymond "Ray" Palmer, is a physicist and professor at Ivy University in the fictional city of Ivy Town, somewhere in New England, specializing in matter compression as a means to fight overpopulation, famine and other world problems. Using a mass of white dwarf star matter he finds after it lands on Earth, Palmer fashions a lens that enables him to shrink any object to any degree he wishes. Compression destabilizes an object's molecular structure, however, causing it to explode. Source: Wikipedia

It's also the epitome of escapist fiction, since a white dwarf in real life is kind of dense.

Imploding hydrogel shrinks objects to the nanoscale, Belle Dumé, Physics World

Nanoglue...

Illustrations of frequency-dependent toughening in a polymer-metal-nanoglue-ceramic composite. Credit: Rensselaer Polytechnic Institute

Topics: Materials Science, Metamaterials, Nanotechnology

In a discovery that could pave the way for new materials and applications, materials scientists at Rensselaer Polytechnic Institute have found that oscillating loads at certain frequencies can lead to several-fold increases in the strength of composites with an interface that is modified by a molecular layer of "nanoglue."

A newly published article in Nature Communications reports the unexpected discovery of the effects of loading frequency on the fracture energy of a multilayer composite involving a "nanoglue," the use of which was also pioneered at Rensselaer.

"Unearthing, understanding, and manipulating nanoscale phenomena at interfaces during dynamic stimuli is a key to designing new materials with novel responses for applications," said Ganpati Ramanath, the John Tod Horton Professor of Materials Science and Engineering at Rensselaer and the lead author on the study. "Our work demonstrates that introducing a nanoglue layer at an interface of a layered composite can lead to large mechanical toughening at certain loading frequencies."

Nanoglue can make composites several times tougher during dynamic loading,
Matthew Kwan et al. Nature Communications, Phys.org

Strange Metals...

Topics: Condensed Matter Physics, Materials Science, Quantum Mechanics, Superconductors

A ubiquitous quantum phenomenon has been detected in a large class of superconducting materials, fueling a growing belief among physicists that an unknown organizing principle governs the collective behavior of particles and determines how they spread energy and information. Understanding this organizing principle could be a key into “quantum strangeness at its deepest level,” said Subir Sachdev, a theorist at Harvard University who was not involved with the new experiments.

The findings, reported today in Nature Physics by a team working at the University of Sherbrooke in Canada and the National Laboratory for Intense Magnetic Fields (LNCMI) in France, indicate that electrons inside a variety of ceramic crystals called “cuprates” seem to dissipate energy as quickly as possible, apparently bumping up against a fundamental quantum speed limit. And past studies, especially a 2013 paper in Science, found that other exotic superconducting compounds — strontium ruthenates, pnictides, tetramethyltetrathiafulvalenes and more — also burn energy at what appears to be a maximum allowed rate.

Universal Quantum Phenomenon Found in Strange Metals, Natalie Wolchover, Quanta Magazine

Proton Pump...

Magneto-ionic switching based on hydrogen accumulation at the metallic ferromagnet/nonmagnetic heavy metal interface. Courtesy: G Beach

Topics: Electrical Engineering, Electromagnetism, Materials Science, Semiconductor Technology, Spintronics

Researchers at the Massachusetts Institute of Technology say they have discovered a new way to electrically control magnetism using a gate voltage that could be applied to a wide variety of magnetic materials, including oxides and metals. The “magneto-ionic” technique, which involves reversibly inserting and removing protons into the material structures, could help advance the field of spintronics (a technology that exploits the spin of the electron rather than its electrical charge) for the post CMOS-world.

Complementary metal-oxide semiconductor (CMOS) technologies are reaching the end of their road map and scientists are looking for alternatives to silicon microchips. Spintronics devices show promise in this context because they retain their magnetic state even when the power supply is switched off, something that it is not true for silicon memory chips. They also require much less power to operate and generate far less heat than their silicon counterparts.

One of the most important phenomena being studied in spintronics today is spin-orbit coupling, explains MIT Materials Research Laboratory co-director Geoffrey Beach, who led this research effort. “In many spintronics systems, emergent effects are generated at the interface between, for example, a metallic ferromagnet and a nonmagnetic heavy metal (like platinum or palladium),” he says. “Heavy metal/ferromagnetic interfaces have long been exploited to engineer magnetic thin films with perpendicular magnetic anisotropy, that is, films that spontaneously magnetize in a direction perpendicular to the film plane, which is required for most applications.”

Controlling magnetism using a proton pump, Belle Dumé, Physics World

Mesh and Eyes...

Schematic showing nonsurgical injection of mesh electronics into the vitreous body of the eye, allowing conformal coating of the mesh on the surface of retina for electrophysiological recording of individual retinal ganglion cells in live animals. Credit: Lieber Group, Harvard University. All rights reserved

Topics: Biology, Materials Science, Optics, Research

Mesh electronics, a macroporous network of components with mechanical properties similar to that of biological tissue, is a relatively new technology that can be used to probe activity in the brain. Now, researchers at Harvard University in the US have developed an injectable mesh that can record the neural activity of mouse eyes in vivo. The device, which does not interfere with eye movement or light-processing, could help neuroscientists study the fundamental properties of primary vision input retinal ganglion cells (RGCs) and how these cells connect with other vision-related brain regions for the first time. The work could also help in the development of retinal prosthetics for restoring vision through non-surgical procedures.

“Mesh electronics is a submicron-thick, large-area macroporous network,” explains team leader Charles Lieber. “We fabricate the meshes as flat 2D sheets using standard semiconductor photolithography-based techniques and suspend them (like a colloid) in aqueous solution. Our specific design, which we first reported on back in 2015, enables mesh electronics to be rolled up into a tubular structure and drawn into a syringe needle.”

On the scale of a single neuron

“We can deliver these structures into specific brain regions with a spatial precision of 20 microns (which is on the scale of a single neuron) using the controlled injection approach we developed. This allows us to control the rate at which we withdraw the needle during injection and means that the mesh structure remains fully extended in the dense tissue of the brain during injection and does not crumple.”

In their new work Lieber and colleagues “non-coaxially” injected the mesh electronics onto the highly curved retinal cup of the eye. As the structure unrolls it forms a stable recording interface to RGCs, which process visual information received by photoreceptors (rods and cones). The researchers then did a series of experiments.

Injectable mesh electronics opens up a new window into vision research
Belle Dumé, Physics World

Cephalopod IR...

Warning signs: the greater blue-ringed octopus changes its appearance when threatened using techniques that have inspired an adaptive infrared reflector. (CC BY-SA 2.5/Jens Petersen)

Topics: Bioengineering, Biology, Optical Physics, Materials Science, Nanotechnology

A simple device with tuneable infrared reflectivity has been made by mimicking the adaptive properties of the skin of octopuses and related animals. Chengyi Xuat, Alon Gorodetsky and George Stiubianu of the University of California, Irvine created the device using a dielectric elastomer and say that it overcomes many of the limitations of previous adaptive infrared-reflecting systems.

Reflecting infrared radiation is important for many technologies, ranging from building insulation to spacecraft components. But most of the materials used to reflect radiation in the infrared region are static: they are unable to respond and adapt to changes in the environment. Some adaptable infrared-reflecting systems have been developed, but they tend to be complex and difficult to control, while also lacking spectral tunability and requiring high operating temperatures.

Inspired by the skin of cephalopods – squid, octopuses, and cuttlefish – Gorodetsky and colleagues have now developed an adaptable infrared-reflecting system that they say is easy to control, can respond rapidly and be used repeatedly. The system also has a tuneable spectral range and works at low temperatures.

Many cephalopods can rapidly change the colour and patterning of their skin. This is done for both camouflage and signalling, and is enabled by pigment cells with adjustable spectral properties that can response within hundreds of milliseconds. These yellow, red, and brown cells, known as adaptive chromatophores, are packed with pigment granules and can be expanded and contracted by radial muscles. As their size and shape changes so do the wavelengths of light that they absorb and reflect.

Octopus skin inspires new infrared reflector, Michael Allen, Physics World