Physicists have realized the idea of the creation of metamaterials based on exotic thermal devices that control the flow of heat — insulating, hub, and an inverter. Scientists' work is accepted for publication in the journal Physical Review Letters, and its short description can be found on the website ScienceNow.
In homogeneous materials heat moderately distributed along a gradient — from hot to cool. But there are materials that possess different thermal conductivity in different directions. This feature is more pronounced in the so-called metamaterials — composite laminates, whose characteristics depend largely on the structure, not the chemical composition.
Earlier arithmetic suggested using metamaterials for creating passive thermal devices, the propagation of heat in what is an unusual way. Among them were thermal cloaks of invisibility, heat concentrators and inverters. For the invention of thermal variations of these devices has inspired scientists introduction of metamaterials for the creation of optical invisibility cloaks.
For example, the proposed thermal cloaks of invisibility is a typical layered shell of metamaterials, conductive heat so that the outside observer could not see the presence of foreign objects inside the shell. The thickness of the shell layer, their number and thermal conductivity was calculated by mathematicians such Makar, so the heat passing through the layers, the envelope hidden object, and the gradient of the heat recovered. Thermal concentrator, however, direct the flow of heat through the chosen object and the inverter locally unfolded thermal flow in the opposite direction.
In true physics paper outlined the creation of real prototypes designed thermal devices. They consisted of small iron core surrounded by 40 layers of rubber and silicone elastomer filled with boron nitride. The core along with the shell makers have filled in a transparent resin to which on the one hand, heat was applied, and the other cooled. For distribution of heat in the device was observed using infrared camera.
Depending on the configuration of the layers (they would be open, closed, "twisted"), this device is a hub, inverter or thermal invisibility cloak.
The creators put their trust that the acquired unit will be the basis for the creation of thermal computers — computers, whose work will be a means of manipulation of heat flow, not electricity. Heat, which for ordinary computers is unnecessary byproduct for future thermal devices can be become energy source. Work on such devices is still in the beginning.
Silicon spheres posodeystvuyut in developing invisibility cloak
Silicon spheres with a diameter of 100-200 nm can serve as a constituent "building blocks" invisibility cloak, which will be able to hide objects in the optical spectrum.
Invisibility cloak — a hardened term applied to structures used for masking objects from electrical surges. Usually arranged in such a disguise makarom that the electric wave, after a meeting with the object in a cloak does not differ from the waves before the meeting. This means that the wave will not be a meeting of disk imaging, in other words, the object is invisible to this wave.
On the real moment of greatest success achieved by masking for a narrow range of wavelengths in the infrared range. This is due to the fact that meta-materials (composite materials, the characteristics of which are determined largely artificially made by repeating structure) similar to the waves easier to create — the size of parts of the structure of the metamaterial must be of the same order as the wavelength, and in the case of the infrared spectrum in question a micrometer wavelengths.
In the infrared invisibility cloak base part are resonators. As part of the latest work of an international team of researchers has found that the role of these resonators can perform silicon spheres with a diameter of several hundred nanometers. It was set up in a series of tests. Scientists also point out that the creation of similar areas is relatively cheap.
Lenses of metamaterials will be able to bend the beam at least some angle
French physicists have developed a scheme of the device is curved beams of light or sound at least some desired angle. The work of scientists is available in the journal New Journal of Physics.
The creators decided to use the principles behind the creation of device-based "invisible" to control the flow of light. "Invisibility cloak" is a multi-layer film, passing through which, the light (or sound) waves are bent in such a Makarov, it is not realistic to find the presence of obstacles in their way. If the shell is inside any object, it is nestled device and is not visible from the outside.
The creators of the study changed the mathematical apparatus developed for the creation of such "invisibility cloaks" to make the device, deflecting the propagation of light like a lens. But unlike conventional lenses, these devices could deflect at least some light on this angle, right until turn (180 degrees) and rotation to form a loop (360 degree). In addition, the creators managed to make light and sound "black hole" in which there is complete absorption of the waves.
Devices with such exotic optical quality can have a huge number of applications, many of which are difficult to predict. For example, they can be used for the creation of a more effective optical fibers, because when wriggling optical fiber close to 90 degrees, it increases the percentage of loss of light, which has a bad effect on the quality of communication. Lenses, deploying light in optical fibers could have done better signal transmission.
Work on the devices become invisible, likely due to the invention of metamaterials, unusual characteristics of which (for example, a negative index of refraction) depend not only on the composition of many of their internal structure. Previously, scientists have suggested the use of metamaterials for the creation of a "dark hole" of microwave radiation.
Arithmetic invented thermal invisibility cloak
A group of French researchers running Sabastena Gene proposed method is the creation of devices that hide objects from the thermal flow. Article posted in the journal Optics Express.
The researchers used the ideas that were previously used for the creation of "invisibility cloaks" that hide objects from waves — electric, acoustic and others. Because the current heat is described by other definitions, the researchers had to significantly revise these ideas.
The idea proposed by scientists device then looks way: inside the material, the heat flowing from the hot to the cool body is spherical multilayer shell layers which have different thermal conductivity. Because of this heat flow curve around the inside of the shell.
As a result, in the 1-x, the inside temperature remains unchanged at 2-x, the temperature gradient of the object is aligned, making the presence of at least some of the object inside the casing inconspicuous (from the standpoint of temperature) for the external observer.
In addition to thermal "insulator", the same principles and makers developed thermal "hub" thermals focusing in one point. If based on the model developed by mathematicians will make working device, it is likely to be broadly to microelectronic industry. Thermal insulation of sensitive components and teplootvedenie are some of the main problems of the area.
Scientists are hard at wor
k on the creation of a fundamentally similar devices that make objects invisible for the electric light. Fundamentally the possibility of their creation has emerged with the inventions of metamaterials, which are unusual features (for example, a negative index of refraction) depend not only on the composition of many of their internal structure.
Earlier Sebastien Gene et al proposed the use of the device to a fundamentally similar scheme for the isolation of objects, such as buildings, from the propagation of seismic waves. This would protect against earthquakes of old buildings, which are not designed for seismic loads.
Physicists have for the first time made a three-dimensional object invisible to microwaves
Scientists have for the first time in practice did object invisible in the microwave spectrum. The article appeared in the scientific journal New Journal of Physics, a brief statement of its leading Institute of Physics.
In the part of the researchers coated iron cylinder 18 cm layer of plasmonic metamaterial. Metamaterials refer to such materials, the characteristics of which are determined largely by their structure rather than composition. In turn, "plasmon" in the title means that especially in these materials behave quasi-plasmons (quanta of free oscillations of the electric gas).
Coating characteristics were such that the scattered radiation is reflected and cancel themselves. As a consequence, the object was invisible to the waves. Experience has shown that it is best represented by the scientists cover hides objects from radiation with a frequency of 3.1 gigahertz. The results of practical experience have been proved by computer simulation.
The researchers note that they have acquired the results can be used in order to hide the object in the optical spectrum. Coupled with the fact arranged in such a way makarom that the size of objects that can be made invisible, is dependent on the wavelength of the electric light.
In 2009, two groups of physicists immediately announced that they were able to get supplies of invisibility, "working" in the infrared spectrum. The facilities have been designed in such a Makarov that the radiation flow around as needed placed inside the object. To work the researchers used silicon.