Metamaterial turns an insulator into a metal

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A golden antenna turns an insulator into a metal
Matthew Francis | July 16 2012 | Ars Technica

'Most normal metals are conductors from very low temperatures up to their melting point, or are insulating under all normal conditions. Vanadium dioxide (VO2) is a weird substance that can suddenly transition from an insulator to a conductor. The rapid shift in the behavior of VO2 can be induced by increasing the temperature, exposing the material to strong light, placing it in an electric field, and other stimuli. But the exact mechanism underlying the transition is unknown.'


Photo: A gold "antenna" used to enhance an oscillating electric field
Credit: Ars Technica

'The main difference between metals and insulators lies in how tightly electrons are bound to their atoms. In metals, the outermost electrons are very loosely bound and form a kind of fluid, so that individual electrons can no longer be associated with a particular atom. This fluid flows easily as an electric current under the right external stimuli. Insulators' electrons are tightly bound, and so they have extreme difficulty moving beyond their host atom.

That's why the insulator-metal transition (IMT) is strange: since the metallic or insulator character depends on the atoms, it's unusual for a single material to transition between one type of behavior and the other. However, prior studies persuasively argued that the IMT must be due to interactions between the electrons in some way.'

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Fascinating material no doubt - from Wiki:

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Another couple of interesting artiles about this fascinating substance:

Reversible Doping: Hydrogen Flips Switch On Vanadium Oxide

Scientists Crack Materials Mystery in Vanadium Dioxide

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Fascinating stuff Continuity - thks for the links!

Accelerated Electrons Bend Light The Wrong Way
Rachel Courtland | August 02, 2012 | IEEE Spectrum

'A new metamaterial, built from two semiconducting layers, has been shown to have an unprecedented ability to refract light in the wrong direction.


Credit: IEEE Spectrum

When light moves from one medium to another, the change in speed causes it to bend or refract. The refractive power of any one material is measured by its index of refraction. For naturally occurring materials, this index of refraction is positive and typically has a value of 5 or less.

Metamaterials (I do not like using Wikipedia - I apoligise for the links), which can be built in a range of ways by using, say nanoparticles or bent arrangements of wire, can bend light differently, exhibiting a property called negative refraction. They’ve been eyed for a range of applications, from invisibility cloaks to light manipulating devices that can beat the physical limitations of conventional materials. Most metamaterials have been created with negative indexes of refraction in the same rough range as naturally occurring materials (although they boast the opposite sign), says Donhee Ham at Harvard University. But, as Ham and his colleagues report today in Nature, there is a way to create "extraordinarily strong" negative refraction. The team built semiconductor devices with negative refractive indexes as low as -700, a hundred times lower than what's seen in most metamaterials, and, Ham suspects, the strongest yet seen. What's more, he says, the device can manipulate microwaves in area that’s about 1/10,000th the size of what’s needed for metamaterials that use wire-based devices like split ring antennas.'

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New form of carbon is so hard it can indent diamond
Aug 16, 2012 | Physics World

'A new form of carbon that is hard enough to indent diamond has been created by a team of researchers from the US and China. The new material, known as ordered amorphous carbon clusters (OACC), is structurally unique in having both crystalline and disordered elements. Created by a team led by Lin Wang of the Carnegie Institution for Science in the US, the material was made by subjecting solvated carbon-60 molecules to phenomenal pressures more than 300,000 times that of the atmosphere.


Credit: Physic World

Carbon comes in many guises, including graphite, diamond, nanotubes, graphene and charcoal. But until now, all have been classified as either crystalline – built from repeating atomic units – or amorphous, that is, lacking the long-range structural order seen in crystals. As a crystalline material composed of amorphous clusters, OACC is the first hybridized carbon structure ever seen that is part amorphous and part crystalline.'

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'Memristors' Based On Transparent Electronics Offer Technology of the Future
Oregon State University | Sep. 14, 2012 | ScienceDaily

'The transparent electronics that were pioneered at Oregon State University may find one of their newest applications as a next-generation replacement for some uses of non-volatile flash memory, a multi-billion dollar technology nearing its limit of small size and information storage capacity.

Researchers at OSU have confirmed that zinc tin oxide, an inexpensive and environmentally benign compound, has significant potential for use in this field, and could provide a new, transparent technology where computer memory is based on resistance, instead of an electron charge.

The findings were recently published in Solid-State Electronics, a professional journal.

This resistive random access memory, or RRAM, is referred to by some researchers as a "memristor." Products using this approach could become even smaller, faster and cheaper than the silicon transistors that have revolutionized modern electronics -- and transparent as well.

Transparent electronics offer potential for innovative products that don't yet exist, like information displayed on an automobile windshield, or surfing the web on the glass top of a coffee table.'

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Water-Splitting Catalyst Revealed
Dexter Johnson | November 09, 2012 | IEEE Spectrum

'This detailed imaging of how photosynthesis splits water into its constituent parts has been held out as a way to help engineers more cheaply synthesize hydrogen gas to power hydrogen fuel cells—and possibly the automobiles powered by them. Research efforts to split water molecules into hydrogen gas have been taken on both by commercial entities and the academics. Perhaps this new information on the electronic structure of the water-splitting process of photosynthesis can further inform both these lines of research.'

Related: Team demonstrates new hybrid nanomaterial for power generation

Related: Conductance measurements on graphene nanoribbons tell researchers how molecular wires can be optimised

Related: First noiseless single photon amplifier

Related: Making a better invisibility cloak

Related: Touch-Sensitive, Self-Healing Artificial Material

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Material That Sorts Molecules by Shape Could Lower the Price of Gas
Kevin Bullis | May 23, 2013 | Technology Review

A hydrocarbon-sorting material could replace energy-intensive oil refining steps.

'A new material that sorts hydrocarbon molecules by shape could lower the cost of gasoline and also make the fuel safer by reducing the need for certain additives that have been linked to cancer, according to a paper in the next issue of the journal Science. Refiners typically use a material that can sort molecules by size during a key step in the refining process. To achieve a desired octane rating, this step has to be supplemented with energy-intensive distillation steps, or by the use of additives. The new material, which sorts molecules by shape rather than by size, can better differentiate between different types of hydrocarbon molecules, eliminating the distillation steps and the need for octane-enhancing additives.
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