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Category: materials

Invisibility cloaks are designed to bend light around an object, but materials that do this are typically hard to shape and only work from narrow angles — if you walk around the cloaked object, for instance, it’s visible. But a new cloak avoids that problem, and is thin and flexible enough to be wrapped around an object of any shape, the researchers said. It can also be “tuned” to match whatever background is behind it — or can even create illusions of what’s there, they added.

Led by Xiang Zhang, director of materials science at Lawrence Berkeley National Laboratory, the group constructed a thin film consisting of a 50-nanometer-thick layer of magnesium fluoride topped by a varying pattern of tiny, brick-shaped gold antennas, each 30 nanometers thick. (For comparison, an average strand of human hair is about 100,000 nanometers wide.) The “bricks” were built in six different sizes, ranging from about 30 to 220 nanometers long and 90 to 175 nanometers wide. [Now You See It: 6 Tales of Invisibility in Pop Culture]

The scientists then wrapped up a tiny, irregularly shaped object measuring about 36 microns across, or a bit more than one-thousandth of an inch. Shining a light, with a wavelength of 730 nanometers, or near-infrared, they found that it reflected back almost perfectly. The light scattering from the cloak still bounced off the object, but without revealing where the object was — as though there were just a flat mirror in its place, the researchers said.

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Invisibility cloaks are a staple of science fiction and fantasy, from Star Trek to Harry Potter, but don’t exist in real life, or do they? Scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have devised an ultra-thin invisibility “skin” cloak that can conform to the shape of an object and conceal it from detection with visible light. Although this cloak is only microscopic in size, the principles behind the technology should enable it to be scaled-up to conceal macroscopic items as well.

Working with brick-like blocks of gold nanoantennas, the Berkeley researchers fashioned a “skin cloak” barely 80 nanometers in thickness, that was wrapped around a three-dimensional object about the size of a few biological cells and arbitrarily shaped with multiple bumps and dents. The surface of the skin cloak was meta-engineered to reroute reflected waves so that the object was rendered invisible to optical detection when the cloak is activated.

“This is the first time a 3D object of arbitrary shape has been cloaked from ,” said Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division and a world authority on metamaterials — artificial nanostructures engineered with electromagnetic properties not found in nature. “Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects.”

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Nighttime solar panels, night solar panels, night photovoltaics, Solar cells, solar power at night, idaho national laboratory, solar technology, solar film, nanotechnology solar, nanoantennas, New Solar Panels Can Harvest Energy After Dark

Despite the enormous untapped potential of solar energy, one thing is for sure- photovoltaics are only as good as the sun’s rays shining upon them. However, researchers at the Idaho National Laboratory are close to the production of a super-thin solar film that would be cost-effective, imprinted on flexible materials, and would be able to harvest solar energy even after sunset!

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Stem cells coming along nicely, Stanford demonstrate how creating artificial stem cell niches improve grafting and regeneration of bone and it should have a broad application for other tissues. Properly developed we could regenerate organs and tissues by injecting enough stem cells in these manufactured protective niches.

One could potentially take it a stage further and modify the stem cells with genes of interest to make them more robust. Ex-vivo cell manipulation is also considerably cheaper than in-vivo therapy.

New porous hydrogel could boost success of some stem cell-based tissue regeneration, researchers say.

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Is this thing on? That’s likely what Hong Kong University of Science and Technology scientists thought, shortly after they’d developed a new system that absorbs 99.7 percent of all the sound that hits it.

Many systems use sonic insulators to deaden sound: materials which absorb sound, typically over a small range of frequencies. By combining different insulators into a composite, it’s possible to absorb a large range of sounds — but it’s difficult to create such a material that absorbs all the the frequencies. It would just be too big and complex. That means that there’s a limit to the amount of sound they can absorb.

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Rice University researchers discovered that putting nanotube pillars between sheets of graphene could create hybrid structures with a unique balance of strength, toughness and ductility throughout all three dimensions.

Carbon nanomaterials are common now as flat sheets, nanotubes and spheres, and they’re being eyed for use as building blocks in hybrid structures with unique for electronics, heat transport and strength. The Rice team is laying a theoretical foundation for such structures by analyzing how the blocks’ junctions influence the properties of the desired materials.

Rice materials scientist Rouzbeh Shahsavari and alumnus Navid Sakhavand calculated how various links, particularly between carbon nanotubes and graphene, would affect the final hybrid’s properties in all directions. They found that introducing junctions would add extra flexibility while maintaining almost the same strength when compared with materials made of layered graphene.

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Scientists have designed a novel type of nanoscale solar cell. Initial studies and computer modelling predict these cells will outperform traditional solar panels, reach power conversion levels by over 40 percent.

Solar power cells work through the conversion of sunlight into electricity using photovoltaics. Here solar energy is converted into direct current. A photovoltaic system uses several solar panels; with each panel composed of a number of solar cells. This combines to create a system for the supply usable solar power.

To investigate what is possible in terms of solar power, the researchers have examined the Shockley-Queisser limit for different materials. This equation describes the maximum solar energy conversion efficiency achievable for a particular material, allowing different materials to be compared as candidates for power generation.

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Concrete is probably one the most used building materials. But one of the foremost challenges when building with this material is its propensity to crack, both when it dries, and in the years that follow. In order to solve this problem, Dutch researchers invented self-fixing concrete, just the way your body restores itself after being wounded.

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Synthetics startup Ras Labs is working with the International Space Station to test “smart materials” that contract like living tissue. These “electroactive” materials can expand, contract and conform to our limbs just like human muscles when a current moves through them – and they could be used to make robots move and feel more human to the touch.

Ras Labs co-founder Lenore Rasmussen accidentally stumbled upon the synthetic muscle material years ago while mixing chemicals in the lab at Virginia Tech. The experiment turned out to be with the wrong amount of ingredients, but it produced a blob of wobbly jelly that Rasmussen noticed contracted and expanded like muscles when she applied an electrical current.

It would be years later when Rasmussen’s cousin nearly lost his foot in a farming accident that she would start to employ that discovery to robotic limbs and space travel. The co-founder thought her cousin might lose his foot and started researching prosthetics.

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This illustration shows a prototype device comprising bare nanospring photodetectors placed on a glass substrate, with metal contacts to collect charges (credit: Tural Khudiyev and Mehmet Bayindir/Applied Optics)

Researchers from Bilkent University, Ankara, Turkey, have shown that twisting straight nanowires into springs can increase the amount of light the wires absorb by up to 23 percent. Absorbing more light is important because one application of nanowires is turning light into electricity, for example, to power tiny sensors instead of requiring batteries.

If nanowires are made from a semiconductor like silicon, light striking the wire will dislodge electrons from the crystal lattice, leaving positively charged “holes” behind. Both the electrons and the holes move through the material to generate electricity. The more light the wire absorbs; the more electricity it generates. (A device that converts light into electricity can function as either a solar cell or a photosensor.)

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