MMaterialsgateNEWS vom 27.10.2014

Verwandte MaterialsgateCARDS

Three-dimensional metamaterials with a natural bent

Metamaterials, a hot area of research today, are artificial materials engineered with resonant elements to display properties that are not found in natural materials. By organizing materials in a specific way, scientists can build materials with a negative refractivity, for example, which refract light at a reverse angle from normal materials.

However, metamaterials up to now have harbored a significant downside. Unlike natural materials, they are two-dimensional and inherently anisotropic, meaning that they are designed to act in a certain direction. By contrast, three-dimensional natural materials typically look the same from all directions. For instance, water in a glass acts as an isotropic material for light, even though the water molecule itself has an asymmetric and anisotropic structure.

Scientists have been able to manufacture three-dimensional isotropic metamaterials, but up to now only on a very small scale. Now, in a significant breakthrough, published in Advanced Optical Materials, scientists from RIKEN, in collaboration with colleagues from ITRC, NARLabs in Taiwan, have succeeded in creating a large metamaterial, up to 4 mm x 4 mm2 in size, that is essentially isotropic, using a type of metamaterial element called a split-ring resonator (SRR).

The team achieved this breakthrough based on a new fabrication technique that combines top-down electron lithography and a bottom-up self-folding mechanism caused by the intrinsic stress of metals, called the "metal-stress driven self-folding method."

They began with the top-down process. They deposited a layer of PMMA, a polymer, on a substrate of silicon. They then used electron beam lithography to etch a ribbon-shaped ditch in the polymer, and then deposited a metallic strip made of nickel and gold. Following this, they removed all of the metal film outside of the ditch. From then the process became bottom-up. They eliminated the silicon except for a small button in the center ribbon of the strip, and when the chip was exposed to air, the stresses on the metal strips led them to form upward into a ring, creating a three-dimensional metamaterial resonator. Essentially, the tension within the materials themselves was used to cause them to fold. The team then used spectroscopy to find that the materially was unambiguously and remarkably isotropic when rotated in any direction up to an incident angle of 40 degrees. These optical properties of the SRR were also supported by three-dimensional electromagnetic numerical calculations.

The team's results demonstrate a promising method for manufacturing highly symmetric metamaterials, leading to isotropic optical responses. According to Takuo Tanaka of the RIKEN Metamaterials Laboratory, who led the research team, "We anticipate that our technique will be a breakthrough for bringing the concepts of metamaterials into real components, especially at optical frequencies. The manufacturing technique we have presented could be extended to stacking by depositing multiple layers, allowing us to build even more complex three-dimensional meta-atoms with interesting optical properties." Metamaterials have been touted for their potential to create "superlenses," which enable us to go beyond the diffraction limit of conventional lenses, and cloaking devices, and the team's achievements could bring those dreams closer to reality.

Source: RIKEN - 24.10.2014.

Recherchiert und dokumentiert von:

Dr.-Ing. Christoph Konetschny, Inhaber und Gründer von Materialsgate
Büro für Material- und Technologieberatung
Die Recherche und Aufbereitung der in diesem Dokument genannten Daten erfolgte mit größter Sorgfalt.
Für die Richtigkeit, Gültigkeit, Verfügbarkeit und Anwendbarkeit der genannten Daten übernehmen wir zu keinem Zeitpunkt die Haftung.
Bitte diskutieren Sie die Verwendung und Eignung für Ihren konkreten Anwendungsfall mit den Experten der genannten Institution.

Sie wünschen Material- und Technologierecherchen zu diesem Thema?

Materialsgate steht für hochwertige Werkstoffberatung und innovative Materialrecherchen.
Nutzen Sie unseren Beratungsservice

MMehr zu diesem Thema

Rice lab creates RGB color display technology with aluminum nanorods

The quest to create artificial "squid skin" -- camouflaging metamaterials that can "see" colors and automatically blend into the background -- is one step closer to reality, thanks to a breakthrough color-display technology unveiled this week by Rice University's Laboratory for Nanophotonics (LANP). The new full-color display technology uses aluminum nanoparticles to create the vivid red, blue and green hues found in today's top-of-the-line LCD televisions and monitors. The technology is described in a new study that will be posted online this week in the Early Edition of the Proceedings of the National Academy of Sciences (PNAS). The breakthrough is the latest... mehr mehr lesen

Trotz aller Fortschritte gibt es noch immer nicht für alle gewünschten Frequenzen geeignete Laser-Systeme. Manche dieser Frequenzen kann man mit Frequenzverdopplern erzeugen, die nichtlineare optische Eigenschaften nutzen.

Wissenschaftler der Technischen Universität München (TUM) und der University of Texas (Austin, USA) haben nun einen optischen Baustein entwickelt, dessen nur 400 Nanometer dicke Schicht, 100-mal dünner als ein menschliches Haar, verschiedenste Frequenzen verdoppeln kann und eine Million mal effizienter ist als traditionelle Materialien mit nichtlinearen optischen Eigenschaften. Laser haben sich für viele Anwendungen fest etabliert. Doch noch immer gibt es Wellenlängen, für die es keine oder nur sehr große und teure Systeme gibt. Andererseits werden für die Sensorik und für medizinische Anwendungen kompakte Lasersysteme gesucht, beispielsweise für Wellenlängen vom nahen Infrarot... mehr mehr lesen

A specially formed material that can provide custom broadband absorption in the infrared can be identified and manufactured using "genetic algorithms," according to Penn State engineers, who say these metamaterials can shield objects from view by infrared sensors, protect instruments and be manufactured to cover a variety of wavelengths.

"The metamaterial has a high absorption over broad bandwidth," said Jeremy A. Bossard, postdoctoral fellow in electrical engineering. "Other screens have been developed for a narrow bandwidth, but this is the first that can cover a super-octave bandwidth in the infrared spectrum." Having a broader bandwidth means that one material can protect against electromagnetic radiation over a wide range of wavelengths, making the material more useful. The researchers looked at silver, gold and palladium, but found that palladium provided better bandwidth coverage. This new metamaterial is actually made of layers on a silicon substrate or base. The first layer is palladium, followed... mehr mehr lesen

In many respects, metamaterials are supernatural. These manmade materials, with their intricately designed structures, bend electromagnetic waves in ways that are impossible for materials found in nature.

Scientists are investigating metamaterials for their potential to engineer invisibility cloaks — materials that refract light to hide an object in plain sight — and “super lenses,” which focus light beyond the range of optical microscopes to image objects at nanoscale detail. Researchers at MIT have now fabricated a three-dimensional, lightweight metamaterial lens that focuses radio waves with extreme precision. The concave lens exhibits a property called negative refraction, bending electromagnetic waves — in this case, radio waves — in exactly the opposite sense from which a normal concave lens would work. Concave lenses typically radiate radio waves like spokes from a wheel... mehr mehr lesen


Partner der Woche

Suche in MaterialsgateNEWS

Bücher und Produkte