Phys.org March 7, 2019 Based on the premise that metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, researchers at Boston University calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves. Using the calculation they created a structure made of plastic that could silence sound from a loudspeaker. In tests they found that 94 percent of the sound emanating from the loudspeaker was imperceptible to the human ear. The shape of acoustic-silencing metamaterials is also completely customizable. […]
Tag Archives: Advanced materials
Magnetization reversal achieved at room temperature using only an electric field
Science Daily February 2, 2019 Researchers in Japan report direct observation of out-of-plane magnetization reversal at room temperature by magnetic force microscopy after electric polarization switching of cobalt-substituted bismuth ferrite thin film grown on GdScO3 substrate. A striped pattern of ferroelectric and weakly ferromagnetic domains was preserved after reversal of the out-of-plane electric polarization. The discovery of magnetic reversal using an electric field paves the way to low power-consumption, non-volatile magnetic memories, such as magnetoresistive random-access memories…read more. TECHNICAL ARTICLE
Unleashing perovskites’ potential for solar cells
MIT News February 7, 2019 Perovskites have attracted a great deal of attention as potential new solar-cell materials because of their low cost, flexibility, and relatively easy manufacturing process. But much remains unknown about the details of their structure and the effects of substituting different metals or other elements within the material. A team of researchers in the US (MIT, UC San Diego, Georgia Institute of Technology, Purdue University, Argonne National Laboratory) found that adding these alkali metals, such as cesium or rubidium, to the perovskite compound helps some of the other constituents to mix together more smoothly making it […]
Magnetic graphene switches between insulator and conductor
Phys.org February 1, 2019 By squashig layers of FePS3 together under high pressure (about 10 Gigapascals) an international team of researchers (UK, South Korea, France, Russia) found that it switched between an insulator and conductor. The conductivity could also be tuned by changing the pressure. These materials are characterised by weak mechanical forces between the planes of their crystal structure. Under pressure, the planes are pressed together, gradually and controllable pushing the system from three to two dimensions, and from insulator to metal. Even in two dimensions, the material retained its magnetism. The research opens possibility for producing two-dimensional materials with […]
Advances in stretchable semiconductors, integrated electronics
Science Daily February 1, 2019 Researchers at the University of Houston introduced metallic carbon nanotubes into a rubbery semiconductor composite enhancing carrier mobility by providing fast paths and, therefore, a shortened carrier transport distance. They developed transistors and their arrays which retained electrical performances without substantial loss when subjected to 50% stretching. Fully rubbery integrated electronics and logic gates they developed functioned reliably upon mechanical stretching. To illustrate one of the applications they demonstrated rubbery active matrix based elastic tactile sensing skin to map physical touch…read more. Open Access TECHNICAL ARTICLE
Waterproof graphene electronic circuits
Science Daily January 30, 2019 Water molecules change the electrical resistance of this carbon material, which introduces a false signal into the sensor. An international team of researchers (Sweden, Germany) discovered that when this two-dimensional material is integrated with the metal of a circuit, contact resistance is not impaired by humidity. They used graphene together with gold metallization and silica substrates in transmission line model test structures, as well as computer simulations to demonstrate their discovery. As part of the European CO2-DETECT project, they are applying this new approach to create the first prototypes of graphene-based sensors to measure carbon […]
Controllable fast, tiny magnetic bits
Phys.org January 4, 2019 Researchers at MIT present an analytical theory to describe three-dimensional magnetic textures in perpendicularly magnetized magnetic multilayers that arise in the presence of magnetostatic interactions and the Dzyaloshinskii-Moriya interaction (DMI). They demonstrated that domain walls in multilayers develop a complex twisted structure, which persists even for films with strong DMI. The origin of this twist is surface-volume stray field interactions that manifest as a depth-dependent effective field whose form mimics the DMI effective field. They found that the wall twist has a minor impact on the equilibrium skyrmion or domain size but can significantly affect current-driven […]
Computer program can translate a free-form 2-D drawing into a DNA structure
Phys.org January 3, 2019 Scaffolded DNA origami offers the unique ability to organize molecules in nearly arbitrary spatial patterns at the nanometer scale, with wireframe designs further enabling complex 2D and 3D geometries with irregular boundaries and internal structures. A team of researchers in the US (MIT, Arizona State University) has developed a fully autonomous procedure to design all DNA staple sequences needed to fold any free-form 2D scaffolded DNA origami wireframe object. The algorithm enables the full autonomy of scaffold routing and staple sequence design with arbitrary network edge lengths and vertex angles. The technique has utility for nanoscale […]
Imperfections make photons perfect for quantum computing
Nanowerk December 17, 2018 Researchers at Rice University found that in molybdenum disulfide a dash of rhenium in just the right spot makes a configuration of atoms with energy states that sit comfortably inside and are isolated from the material’s natural band gap. Aligning magnetic moments of atoms in the defect and exciting them with light brings them to a higher energetic state making them exit as single photon. The direction of the photon is not understood, but the researchers suspect that it is well defined. The defect’s optical transition lies in the optical fiber telecommunication band, which is ideal […]
Graphene on the way to superconductivity
Science Daily November 9, 2018 Previously researchers at MIT showed that it is possible to generate a form of superconductivity in a system of two layers of graphene under very specific conditions using a complex method. Researchers in Germany have developed a simpler technique by heating silicon carbide crystal until silicon atoms evaporate from the surface, leaving first a single-layer of graphene on the surface, and then a second layer of graphene. The two graphene layers are not twisted against each other but lie exactly on top of each other. They argue that their two-dimensional flat band model and the […]