Science Daily February 15, 2022 Terahertz waveguides are required to provide versatile signal-processing functionalities. Despite fundamental components they typically rely on complex hybridization, in turn making it extremely challenging to go beyond the most elementary functions. An international team of researchers (Canada, Italy, Germany) has proposed a universal approach, in which multiscale-structured Bragg gratings can be directly etched on metal-wires. They designed a four-wire waveguide geometry, amenable to support the low-loss and low-dispersion propagation of polarization-division multiplexed terahertz signals. By engraving on the wires judiciously designed Bragg gratings based on multiscale structures, they demonstrated that it is possible to independently […]
It’s in the air – battery discovery takes up the charge
Science Daily February 10, 2022 An international team of researchers (Australia, China, USA – Argonne National Laboratory) describe the details of an Li-O2 battery operated via a new quenching/mediating mechanism that relies on the direct chemical reactions between a versatile molecule and superoxide radical/Li2O2. The battery exhibits a 46-fold increase in discharge capacity, a low charge overpotential of 0.7 V, and an ultralong cycle life greater than 1400 cycles. Redox-active 2,2,6,6-tetramethyl-1-piperidinyloxy moieties bridged by a quenching-active perylene diimide backbone acts as a redox mediator to catalyze discharge/charge reactions and serves as a reusable superoxide quencher to chemically react with superoxide […]
New plant-derived composite is tough as bone and hard as aluminum
MIT News February 10, 2022 So far researchers have been able to incorporate low fractions of the exceptionally strong carbon nanocrystals (CNCs), as the crystals tend to clump and only weakly bond with polymer molecules. To develop a composite with a high fraction of CNCs researcher at MIT determined the ratio of CNC and polymer that would turn the solution into a gel, with a consistency that could either be fed through the nozzle of a 3-D printer or poured into a mold to be cast. When dried the material shrank, leaving behind a solid composite composed mainly of cellulose […]
A proposal to use electric charges to encourage raindrops to form in clouds
Phys.org February 9, 2022 Researchers in the UK calculated the electrostatic forces between two water spheres that have not yet grown large enough to be described as raindrops. They found that the greater the variation in charges between droplets, the stronger the attraction between them. And that led them to suggest that if the variation was increased via an electric charge, the droplets would merge, leading to the formation of rain drops. As droplets merge and grow in size, additional electric charge should result in mergers between droplets until they become large enough for gravity to take over and they […]
Researchers combine piezoelectric thin film and metasurfaces to create lens with tunable focus
EurekAlert February 17, 2022 Using metasurfaces researchers in Norway designed a device in which a metasurface is suspended on a membrane ring made of a thin-film lead zirconate titanate (PZT) film, which allows the PZT to move the metasurface when a voltage is applied. To demonstrate how MEMS-metasurfaces could function as a varifocal lens doublet, they placed a second metasurface lens after the MEMS-metasurface. Varying the separation distance between the lenses through MEMS displacement allowed researchers to tune the focal point of the lens doublet on the fly. The researchers showed that applying 23 volts allowed the PZT membrane to […]
Researchers use solar cells to achieve fast underwater wireless communication
Science Daily February 16, 2022 The greatest problem in using solar panels for underwater wireless optical communication (UWOC) systems is the limited bandwidth of the solar panel, which was originally optimized for energy harvesting rather than communication. Researchers in China studied the fundamentals of the solar array and proposed series-connected solar arrays for high-speed underwater detection. As they increased the size of the solar array from 1×1 to 3×3, the −20-dB bandwidth increased from 4.7 MHz to 24.2 MHz. To further improve the frequency response, they applied a reverse bias on the array. With a reverse bias voltage of 90 […]
Researchers create molecule that can pave way for mini transistors
Phys.org February 15, 2022 Organic molecules consist of aromatic benzene rings, flat rings made up of six carbon atoms, which do not change properties or shape if subjected to electric potential. An international team of researchers (Sweden, Denmark) developed a successful formula to design anti-aromatic hydrocarbons made up of rings with eight carbon atoms. When bent into a tub-shape, it becomes more robust and can both receive and relay electrons. If two electrons are injected into it the hydrocarbon flattens and goes from insulating to conducting—a function like that of a transistor switching from 0 to 1. The combination of […]
Researchers identify mechanism by which fatigue cracks grow
Phys.org February 16, 2022 Over the past century a succession of mechanisms has been hypothesized for structural failures resulting from prolonged low-amplitude loading. By atomistic modeling researchers at Cornell University have shown that sustained fatigue crack growth in vacuum requires emitted dislocations to change slip planes prior to their reabsorption into the crack on the opposite side of the loading cycle. By harnessing a new implementation of a concurrent multiscale method, they assess the validity of long-hypothesized material separation mechanisms thought to control near-threshold fatigue crack growth in vacuum and reconcile reports of crack growth in atomistic simulations at loading […]
Solar-powered system offers a route to inexpensive desalination
Science Daily February 14, 2022 Salt accumulation is one of the key bottlenecks for reliable solar evaporation techniques. An international team of researchers (USA – MIT, China) developed a wick-free layered system, with dark material at the top to absorb the sun’s heat, then a thin layer of water above a perforated layer of polyurethane, sitting atop a deep reservoir of the salty water such as a tank or a pond. Through calculations and experiments they determined the holes size in the polyurethane sheet to be 2.5 mm across for optimal convective circulation between the warmer upper layer of water […]
Squeezing the noise out of microscopes with quantum light
Nanowerk February 14, 2022 Quantum microscopy relies on extremely delicate control of light waves. However, its sensitivity is typically limited by optical losses. A team of researchers in the US (Oak Ridge National Laboratory, Tulane University, MIT, University of Colorado) circumvented the problem with an entangled light called squeezed light, that is, the intensities of the light beams are correlated with each other at the quantum level resulting in noise reduction of up to 3 dB below the standard quantum limit. They minimized the photon backaction noise while taking advantage of quantum noise reduction by transducing the cantilever displacement signal […]