A flexible color-changing film inspired by chameleon skin (w/video)

Nanowerk  October 21, 2020 By tensing or relaxing their skin, chameleons can change the way light reflects from guanine crystals under the surface, producing structural coloration. The structural colors are different from the pigments that give many other creatures their hues. Currently available materials for mimicking chameleon skin is difficult to produce. Researchers in China introduced a flexible network structure in cellulose nanocrystals (CNCs), exerting a bridge effect for the rigid nanomaterials. These films display high flexibility with a fracture strain of up to 39%. Notably, stretching-induced structural color changes visible to the naked eye are realized, for the first […]

Materials scientists discover design secrets of nearly indestructible insect

Nanowerk  October 21, 2020 The ironclad beetle is one formidable insect which has an exoskeleton that is one of the toughest, most crush-resistant structures known to exist in the biological world. An international team of researchers (USA – UC Riverside, Purdue University, UT San Antonio, Lawrence Berkeley National Laboratory, UC Irvine, Japan) used advanced microscopy, spectroscopy and in situ mechanical testing, and identified multiscale architectural designs within the exoskeleton of the beetle, and examined the resulting mechanical response and toughening mechanisms. They highlighted a series of interdigitated sutures, the ellipsoidal geometry and laminated microstructure which provide mechanical interlocking and toughening […]

Liquid metals come to the rescue of semiconductors

EurekAlert  October 11, 2020 In theory the two-dimensional materials can result in transistors that do not waste energy during their on/off switching. However, one of the barriers with the current technologies is that the deposited ultra-thin films are full of grain boundaries so that the charge carriers are bounced back from them and hence the resistive loss increases. An international team of researchers (Australia, UCLA) has developed a new method to eliminate grain boundaries using gallium metal in its liquid state. With its low melting point (29.8 deg C) its surface is atomically smooth when melted providing many free electrons […]

Well-formed disorder for versatile light technologies

Nanowerk  October 13, 2020 In nonlinear crystals, two photons of a particular frequency can be turned into one photon having twice that frequency if they are phase matched. This often severely limits practical applications. Researchers in Switzerland combined resonances and disorder by implementing random quasi-phase-matching in Mie resonant spheres of a few micrometres realized by the bottom-up assembly of barium titanate nanocrystals. The measured second-harmonic generation reveals a combination of broadband and resonant wave mixing, in which Mie resonances drive and enhance the second-harmonic generation, while the disorder keeps the phase-matching conditions relaxed. The nanocrystal assemblies provide new opportunities for […]

Anti-reflective nanocoating inspired by fly eyes

Nanowerk  September 16, 2020 Insect eyes have an anti-reflective coating which has been shown to provide anti-adhesive functionality. Researchers in Switzerland demonstrated a clear link between the morphology and function of the nanocoatings on Drosophila corneas. They found that nanocoatings that consist of individual protrusions have better anti-reflective properties, whereas partially merged structures have better anti-adhesion properties. Using biochemical analysis and genetic modification techniques they reverse engineered the protein Retinin and corneal waxes as the building blocks of the nanostructures and established low-cost production of Retinin. Mixing this synthetic protein with waxes they forward engineered various artificial nanocoatings with insect-like […]

New way of controlling conductivity of materials at the nanoscale

Science Daily  September 16, 2020 Scientists routinely manipulate the flow of electrons to make possible smaller components in computers and mobile phones that use barely any electricity. However, some of the most promising concepts seem mutually exclusive inhibiting the creation of a network. An international team of researchers (Norway, Spain, Switzerland, USA – Lawrence Berkeley National Laboratory, UK, Finland) has developed a new approach based on exploiting ‘hidden’ irregularities at the atomic level, anti-Frenkel defects. Anti-Frenkel defects can be manipulated in such a way that changes in the conductivity do not affect the actual structure of the material or change […]

Physicists discover new magnetoelectric effect

Science Daily  September 14, 2020 An international team of researchers (Austria, Russia, the Netherlands) found that in langasite made of lanthanum, gallium, silicon and oxygen, doped with holmium atoms even small changes in the direction of the magnetic field can switch the electrical properties of the material to a completely different state even though it has a crystal structure that is so symmetrical that it should actually not allow any magnetoelectric effect for theoretical reasons. In the case of weak magnetic fields there is no coupling whatsoever with the electrical properties of the crystal. But if the strength of the […]

Scientists predicted new hard and superhard ternary compounds

EurekAlert  September 4, 2020 An international team of researchers (Russia, Armenia) has predicted new hard and superhard ternary compounds in the tungsten-molybdenum-boron system using computational methods. Mixing tungsten and molybdenum atoms produced compounds that were disordered and, therefore, had varying stability depending on temperature. They predicted five new stable ternary compounds with various chemical compositions at different temperatures and calculated the composition–temperature phase diagrams. Electronic properties of the new compounds were studied in detail to find their correlation with the mechanical properties, crystal structure, and atomic composition…read more. TECHNICAL ARTICLE

Moth-eye nanostructures make good anti-icing coatings

Physics World  September 3, 2020 Researchers in Vietnam fabricated moth eye structure on the quartz substrate covered with a flat paraffin layer to isolate it in a cold and humid environment. The paraffin layer only stayed on the top of the nanostructure, separated it from the outside environment to obstruct heat energy being transferred to the cold substrate, and prevented the wetting transition, which was observed regularly on the rough surface. Numerous air blocks trapped inside the nanostructure also contributed to delayed heat transfer, leading to an increase in the freezing time of the attached water droplet. The nanostructure coated […]

New electronic skin can react to pain like human skin

EurekAlert  September 1, 2020 An international team of researchers (Australia, Bangladesh) combined stretchable electronics, temperature-reactive coatings, and brain-mimicking memory to develop a device that can electronically replicate the way human skin senses pain. They have demonstrated the ability to detect and respond to pressure, temperature, and pain stimuli above a threshold with real‐life performance characteristics with explanation of underlying mechanisms. The research opens a way to better prosthetics, smarter robotics and non-invasive alternatives to skin grafts…read more. Open Access TECHNICAL ARTICLE