Materials

Researchers Build 'Invisible' Materials with Light

Metamaterials have a wide range of potential applications, including sensing and improving military stealth technology. Before cloaking devices can become reality on a larger scale, however, researchers must determine how to make the right materials at the nanoscale. Using light is now shown to be an enormous help in such nano-construction. A new technique uses light like a needle to thread long chains of particles. The development could help bring sci-fi concepts, such as cloaking devices, one step closer to reality.The technique developed by the University of Cambridge team involves using unfocused laser light as billions of needles, stitching gold nanoparticles together into long strings, directly in water for the first time. The strings can then be stacked into layers one on top of the other, similar to Lego bricks. The method makes it possible to produce materials in much higher quantities than can be made through current techniques. SourceAlso: See other Sensors tech briefs.

Posted in: Photonics, Lasers & Laser Systems, Materials, Sensors, Nanotechnology, Defense, News

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Spongelike Structure Converts Solar Energy into Steam

A new material structure developed at MIT generates steam by soaking up the sun.The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation.“Steam is important for desalination, hygiene systems, and sterilization,” says Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”SourceAlso: See other Energy tech briefs.

Posted in: Materials, Solar Power, Energy Harvesting, Energy, News

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Engineers Use Resin Inks, 3D Printing to Build Lightweight Cellular Composites

Like other manufactured products that use sandwich panel construction to achieve a combination of light weight and strength, turbine blades contain carefully arrayed strips of balsa wood from Ecuador, which provides 95 percent of the world’s supply.As turbine makers produce ever-larger blades—the longest now measure 75 meters, almost matching the wingspan of an Airbus A380 jetliner—they must be engineered to operate virtually maintenance-free for decades. In order to meet more demanding specifications for precision, weight, and quality consistency, manufacturers are searching for new sandwich construction material options.Now, using a cocktail of fiber-reinforced epoxy-based thermosetting resins and 3D extrusion printing techniques, materials scientists at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering have developed lightweight cellular composite materials.The work could have applications in many fields, including the automotive industry where lighter materials hold the key to achieving aggressive government-mandated fuel economy standards. SourceAlso: See more Materials tech briefs.

Posted in: Manufacturing & Prototyping, Rapid Prototyping & Tooling, Materials, Composites, Aerospace, Aviation, News

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Nano-Pixels Promise Flexible, High-Res Displays

A new discovery will make it possible to create pixels just a few hundred nanometers across. The "nano-pixels" could pave the way for extremely high-resolution and low-energy thin, flexible displays for applications such as 'smart' glasses, synthetic retinas, and foldable screens.Oxford University scientists explored the link between the electrical and optical properties of phase change materials (materials that can change from an amorphous to a crystalline state). By sandwiching a seven=nanometer-thick layer of a phase change material (GST) between two layers of a transparent electrode, the team found that they could use a tiny current to 'draw' images within the sandwich "stack."Initially still images were created using an atomic force microscope, but the researchers went on to demonstrate that such tiny "stacks" can be turned into prototype pixel-like devices. These 'nano-pixels' – just 300 by 300 nanometers in size – can be electrically switched 'on and off' at will, creating the colored dots that would form the building blocks of an extremely high-resolution display technology.SourceAlso: Learn about Slot-Sampled Optical PPM Demodulation.

Posted in: Electronics & Computers, Board-Level Electronics, Electronics, Imaging, Displays/Monitors/HMIs, Materials, Semiconductors & ICs, Nanotechnology, News

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Inspired by Nature, Researchers Build a Tougher Metal

Drawing inspiration from the structure of bones and bamboo, researchers have gradually changed the internal structure of metals to make stronger, tougher materials. The new metals can be customized for a wide variety of applications — from body armor to automobile parts. The research team tested the new approach in interstitial free (IF) steel, which is used in some industrial applications.If conventional IF steel is made strong enough to withstand 450 megapascals (MPa) of stress, it has very low ductility – the steel can only be stretched to less than 5 percent of its length without breaking. Low ductility means a material is susceptible to catastrophic failure, such as suddenly snapping in half. Highly ductile materials can stretch, meaning they are more likely to give people time to respond to a problem before total failure.The researchers are also interested in using the gradient structure approach to make materials more resistant to corrosion, wear, and fatigue.SourceAlso: Find more Materials tech briefs.

Posted in: Materials, Metals, Transportation, Automotive, Defense, News

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Morphable Surfaces Reduce Air Resistance

A morphable surface developed by an MIT team can change surface texture — from smooth to dimpled, and back again — through changes in pressure. When the inside pressure is reduced, the flexible material shrinks, and the stiffer outer layer wrinkles. Increasing pressure returns the surface to a smooth state. Adding golf ball-like dimples to surfaces could reduce drag and improve efficiency of vehicles.The ability to change the surface in real time comes from the use of a multilayer material with a stiff skin and a soft interior — the same basic configuration that causes smooth plums to dry into wrinkly prunes. To mimic that process, the team made a hollow ball of soft material with a stiff skin — with both layers made of rubberlike materials — then extracted air from the hollow interior to make the ball shrink and its surface wrinkle.Because the surface texture can be controlled by adjusting the balls’ interior pressure, the degree of drag reduction can be controlled at will. “We can generate that surface topography, or erase it,” said MIT’s Pedro Reis. “That reversibility is why this is pretty interesting; you can switch the drag-reducing effect on and off, and tune it.”Many researchers have studied various kinds of wrinkled surfaces, with possible applications in areas such as adhesion, or even unusual optical properties. “But we are the first to use wrinkling for aerodynamic properties,” said Reis.SourceAlso: Learn about other innovative Materials and Coatings.

Posted in: Materials, Coatings & Adhesives, Transportation, Automotive, News

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'Sensing Skin' Detects Damage in Concrete Structures

Researchers from North Carolina State University and the University of Eastern Finland have developed new “sensing skin” technology designed to serve as an early warning system for concrete structures, allowing authorities to respond quickly to damage in everything from nuclear facilities to bridges.“The sensing skin could be used for a wide range of structures, but the impetus for the work was to help ensure the integrity of critical infrastructure such as nuclear waste storage facilities,” says Dr. Mohammad Pour-Ghaz, an assistant professor of civil, construction and environmental engineering at NC State and co-author of a paper describing the work.The skin is an electrically conductive coat of paint that can be applied to new or existing structures. The paint can incorporate any number of conductive materials, such as copper, making it relatively inexpensive.Electrodes are applied around the perimeter of a structure. The sensing skin is then painted onto the structure, over the electrodes. A computer program then runs a small current between two of the electrodes at a time, cycling through a number of possible electrode combinations.Every time the current runs between two electrodes, a computer monitors and records the electrical potential at all of the electrodes on the structure. This data is then used to calculate the sensing skin’s spatially distributed electrical conductivity. If the skin’s conductivity decreases, that means the structure has cracked or been otherwise damaged.The researchers have developed a suite of algorithms that allow them to both register damage and to determine where the damage has taken place.SourceAlso: Learn about Designing Composite Repairs and Retrofits for Infrastructure.

Posted in: Electronics & Computers, Electronic Components, Electronics, Materials, Sensors, Detectors, Test & Measurement, Communications, Semiconductors & ICs, News

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