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Category: materials – Page 256

A pair of researchers at Tokyo Institute of Technology (Tokyo Tech) describes a way of making a submicron-sized cylinder disappear without using any specialized coating. Their findings could enable invisibility of natural materials at optical frequency and eventually lead to a simpler way of enhancing optoelectronic devices, including sensing and communication technologies.

Making objects invisible is no longer the stuff of fantasy but a fast-evolving science. ‘Invisibility cloaks’ using metamaterials—engineered materials that can bend rays of light around an object to make it undetectable—now exist, and are beginning to be used to improve the performance of satellite antennas and sensors. Many of the proposed metamaterials however only work at limited wavelength ranges such as microwave frequencies.

Now, Kotaro Kajikawa and Yusuke Kobayashi of Tokyo Tech’s Department of Electrical and Electronic Engineering report a way of making a without a cloak for monochromatic illumination at optical frequency—a broader range of wavelengths, including those visible to the human eye.

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Scientists from Tomsk Polytechnic University (TPU), together with colleagues from the United States and Germany, have found a way to obtain inexpensive catalysts from hexagonal boron nitride or “white graphene.” The technology can be used in the production of environmentally friendly hydrogen fuel.

The researchers have found a new way to functionalize a dielectric, otherwise known as white graphene, i.e. (hBN), without destroying it or changing its properties. Thanks to the new method, the researchers synthesized a polymer nano carpet with strong covalent bond on the samples.

Prof Raul Rodriguez from the TPU Research School of Chemistry & Applied Biomedical Sciences explains:

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Researchers at the University of Fribourg’s Adolphe Merkle Institute (AMI) and Hokkaido University in Japan have developed a method to tailor the properties of stress-indicating molecules that can be integrated into polymers and signal damages or excessive mechanical loads with an optical signal.

As part of their research activities within the National Center of Competence in Research Bio-inspired Materials, Professor Christoph Weder, the chair of Polymer Chemistry and Materials at AMI, and his team are investigating polymers that change their color or characteristics when placed under mechanical load. The prevailing approach to achieve this function is based on specifically designed sensor that contain weak chemical bonds that break when the applied mechanical force exceeds a certain threshold. This effect can cause a color change or other pre-defined responses. A fundamental limitation of this approach, however, is that the weak bonds can also break upon exposure to light or heat. This lack of specificity reduces the practical usefulness of stress-indicating polymers. It normally also makes the effect irreversible.

Addressing this problem, Weder and Dr. Yoshimitsu Sagara—a Japanese researcher who spent two years in Weder’s group at AMI before joining Hokkaido University as an Assistant Professor—devised a new type of sensor molecule that can only be activated by mechanical force. Unlike in previous force-transducing molecules, no chemical bond breaking takes place. Instead, the new sensor molecules consist of two parts that mechanically interlock. This interconnection prevents the separation of the two parts, while still allowing them to be pushed together or pulled away from each other. Such molecular pushing and pulling causes the molecule’s fluorescence to change from off to on.

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A new and greatly improved version of an electronic tag, called Marine Skin, used for monitoring marine animals could revolutionize our ability to study sea life and its natural environment, say KAUST researchers.

Marine Skin is a thin, flexible, lightweight polymer-based material with integrated electronics which can track an animal’s movement and diving behavior and the health of the surrounding . Early versions of the sensors, reported previously, proved their worth when glued onto the swimming crab, Portunus pelagicus.

The latest and much more robust version can operate at unprecedented depths and can also be attached to an animal using a noninvasive bracelet or jacket. This can, when necessary, avoid the need for any glues that might harm an animal’s sensitive skin.

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The strongest synthetic materials are often those that intentionally mimic nature.

One natural substance scientists have looked to in creating is , also known as mother-of-pearl. An exceptionally tough, stiff material produced by some mollusks and serving as their inner shell layer, it also comprises the outer layer of pearls, giving them their lustrous shine.

But while nacre’s make it an ideal inspiration in the creation of synthetic , most methods used to produce artificial nacre are complex and energy intensive.

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Scientists have developed a first-of-its-kind device that generates electricity from nothing other than the natural phenomenon of snowfall.

Based upon the principles of the triboelectric effect, in which electrical charge is generated after two materials come into contact with one another, the researchers’ new technology exploits the fact that snow particles carry a positive electrical charge.

Because of that, snowflakes give up electrons, provided they get a chance to interact with the right, negatively charged substance.

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Apr 11, 2019 (Heraldkeeper via COMTEX) — Summary:

A new market study, titled “Discover Global Aerogel Market Upcoming Trends, Growth Drivers and Challenges” has been featured on WiseGuyReports.

Introduction

Aerogel, a mesoporous solid foam, is composed of an interconnected nanostructure network with minimum 50% porosity. It consists of low thermal conductivity features, which make it an ideal insulation material. The global aerogel market value was about USD xx million in 2018, and is expected to grow at a CAGR of xx% to reach USD XX million by 2026.

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The Futurecraft Loop performance running shoes can be returned to Adidas, where they will be ground up to make more shoes, again and again.

So, recycling is a mess. Manufacturers have sold us on the idea that it’s the consumer’s responsibility to recycle the manufacturer’s product, ostensibly relieving the manufacturer of responsibility for all the trash their products generate. Meanwhile, despite many of us trying our best to uphold our end of the deal, recycling is complicated – and in the end, 91 percent of plastic, for example, is not recycled.

Given plastic’s nearly eternal durability, it’s little wonder that we’re finding it literally everywhere on the planet. And we keep making new plastic at a prodigious rate – National Geographic notes that “If present trends continue, by 2050, there will be 12 billion metric tons of plastic in landfills.”

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The researchers believe that other MEGOs that absorb, enhance, reflect, or bend waves in new ways could be created using patterned 3D printing. The current Tufts study utilizes stereolithography. Other 3D-printing technologies, such as two-photon polymerization, could provide printing resolution down to 200 nm, which would enable the fabrication of even finer metamaterials that could detect and manipulate electromagnetic signals of even smaller wavelengths, potentially including visible light. As resolution in 3D printing improves, MEGO devices could reach terahertz frequencies.

MEDFORD, Mass., April 9, 2019 — 3D-printed metamaterials developed by a Tufts University engineering team display properties not found in conventional materials. The fabrication methods used by the team demonstrate how stereolithography-based 3D printers can be used to create 3D optical devices through a process that fuses metamaterials with geometrical optics, or MEGO. The MEGO devices can be fabricated at a lower cost than devices made using typical fabrication methods.

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