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Sometimes in life there are situations when we need to ... hide. Or hide some objects from prying eyes. In a word, disguise. This is where modern technology can help us.

In recent years, researchers have managed to create a number of metamaterials (composite materials whose properties are determined not so much by the properties of their constituent elements as by the structure) that do not transmit light, sound, heat, and so on...

Even in the wizarding world of Harry Potter, the invisibility cloak was a rarity.

Optical illusion

To make the person invisible, alas, will not work: for this, the tissues of our body must stop refracting and reflecting light. But even if it is possible to change the human organism for its invisibility, it is still unknown what consequences this will lead to. For example, we can go blind, because invisible eyes will no longer capture the light... Therefore, the best option that will allow us to at least create the illusion of disappearance is to use special "camouflage" materials.

We are talking, for example, about a substance with a negative angle of refraction. As a result, the light rays seem to “envelop” the object, and an outside observer sees only what is behind him, while the object itself remains invisible.

The first step towards the creation of an "invisibility cloak" was made back in the mid-90s of the last century by the physicist of Imperial College London, John Pendry. The scientist suggested using metamaterials for this purpose, which include a metal conducting electricity, as well as a dielectric.

A few years ago, Japanese scientists invented a veil for camouflage. Special sensors attached to the surface give the coverlet the color of the surrounding objects and partially prevent light refraction. Therefore, if a person put on such a cloak, you can see other objects through it!

In 2011, a group of scientists from the University of Barcelona (Spain), led by Alvaro Sanchez, together with colleagues from the Slovak Academy of Sciences, proposed a system for protecting objects from magnetic fields using a ferromagnetic coating. For example, ordinary fridge magnets are made from this material.

The object under the coating becomes impervious to magnetic rays. Thus, it will be possible to make the MRI procedure safer and ... "deceive" the magnetic frames located at train stations and airports.

Not so long ago, a team of physicists from Birmingham managed to create a material with uniaxial silicon nitride crystals on a transparent nanoporous silicon oxide substrate. Nanometer holes were made in the crystals, which turned the material into a smooth optical mirror capable of hiding objects in the visible range.

Canadian camouflage company Hyperstealth has developed Quantum Stealth, a soft fabric that allows light to “circle” around an object, making it invisible not only to the eyes, but also to cameras, and also hides shadows from objects.

Quantum Stealth testing began in 2012. True, at first the material was intended only for the military. In April 2014, the company announced the launch of a commercial version of the "invisibility cloak" - Hyperstealth INVISIB. Perhaps next year the fabric will already go on sale.

Give nanotubes!

Researchers at the University of North Texas at Dallas have developed a technology to "erase" objects using carbon nanotubes. It is based on photothermal refraction, or the mirage effect. The principle of the developed technology is as follows: operators, alternately turning on and off the current supply, heat and cool the material consisting of cylindrical carbon molecules with high thermal conductivity.

At the same time, an object that is behind a veil of this material either appears or disappears ... True, there is one problem: in order to disappear, the object must certainly be placed in a container with water.

In turn, the British company Surrey Nanosystems managed to create "the darkest material on Earth." It reflects only 0.035% of light rays.

The surface of the material, called Vantabalck, is made up of graphite nanotubes 10,000 times thinner than a human hair. Their diameter is so small that it simply does not transmit photons of light. As a result, they fall into the spaces between the tubes and can no longer “get out” from there. The developers hope that the material will find application in optical devices, various electronics and thermal protection systems.

Protein from squid skin

Scientists have long been amazed at the ability of marine animals such as cuttlefish, squid and octopus to remain invisible in the water. Recently, a group of researchers from the University of California and Duke University decided to use this property in the development of camouflage for the Marines.

In the skin of the squid Loligo pealeii, they found the protein reflectin, which is able to adapt to light radiation with different wavelengths. It turned out that in the tissues of this marine life, layers of cells with a high and low refractive index of light alternate. By increasing and decreasing the distance between them, the squid "reflects" light rays of different ranges and mimics.

After isolating reflectin with a high refractive index from squid cells, the researchers placed a layer of the protein on films of graphene oxide and silicon dioxide. Then they began to alternately treat the material with water vapor, then with an acid solution, causing the protein layer to expand, then fall off, while changing color.

Remedy for groping

And specialists from the Karlsruhe Institute of Technology (Germany) have developed a material that can hide objects ... from groping!

“The new type of invisibility cloak is made of a polymeric metamaterial whose properties are determined by a special structure,” says one of the developers, Timo Bückmann. - We managed to build a structure around the object, the resistance of which changes depending on the coordinates.

The structure of the coating consists of thin needle-cones with tips touching each other. Moreover, the size of the contact points is calculated with maximum accuracy: it is this parameter that gives the material the necessary mechanical properties. As a result, if you place any object under the coating, then, touching the material from above, you will never be able to feel it.

So, experimenting, the scientists placed a solid cylinder in the cavity under the coating. Previously, even if the cylinder was covered with sponge material or cotton, this did not "save" him from groping. The researchers failed to find a cylinder under the miracle material.

Now about the most important thing - about the practical application of the discovery. What is it for? Well, suppose you are forced to sleep on a sofa or mattress from which springs bulge out, or on the floor, or on earth and stones - you never know what circumstances ... If you have a cover made of a material that protects against groping, then you will not feel no discomfort.

This is reminiscent of Hans Christian Andersen's fairy tale "The Princess and the Pea," commented Timo Bückmann. - In the fairy tale, the sensitive princess still managed to feel a hard pea under a hundred mattresses. One layer of our material would be enough for the princess to sleep peacefully all night.

The novelty can make shoes more comfortable. If a nail pierces the bottom of your shoes, you simply won't feel it, unless it pierces through the "supermaterial" insole.

Clothing or a bag made of wonderful material will help protect against thieves. As you know, robbers most often first feel things and pockets from the outside in order to find a wallet or mobile phone, and only then they climb there with their hands ...

If you are wearing a jacket, coat or raincoat made of fabric that protects against touch, or if valuables are in a bag made of such a polymer, then the attacker simply will not be able to grope anything. Although if he just gets into his pocket or bag with his hand, then this know-how is unlikely to work. But every rule has its exceptions...

Ida SHAKHOVSKAYA

A fairy tale often becomes a reality. Flying carpets, magic saucers that reflect a distant reality, walking boots and many other inventions have become quite an everyday reality. Now it's time for the invisibility hat. At least the American journal "Science" published an article that outlines the basic principles of operation of an almost ideal camouflage.

Problems of invisibility

The problem of optical secrecy of objects is being studied by scientists from the Department of Materials Science at the Lawrence National Laboratory at the University of Berkeley. Supervised by Mr. Xiang Zhang. The general idea is to make the light bend around an object. Similar developments have already been made in the past, but were not successful for the reason that previous attempts could deflect rays in a narrow angular range. It has not yet been possible to achieve complete optical permeability or its illusion. Distortion of the picture allows you to locate the object (that is, its visual detection). The lack of flexibility of masking surfaces was also a problem. All these shortcomings are devoid of ultra-thin material developed at Berkeley. The "cloak" invented at Lawrence National Laboratory is flexible, but still too expensive.

Operating principle

The role of storytellers in our time is played by filmmakers. In the movie Predator, the Alien (an antagonistic character) uses a cloaking device to stealthily approach his victims. The effect is far from perfect: the alien is given out by light distortions. It is not transparent (although it is not so easy to detect the enemy), in its place there is a certain haze. Reality surpassed the director's wildest dreams. The "cloak", invented at the Lawrence National Laboratory, makes the object truly invisible.

The principle of operation is that many microscopic mirrors automatically turn in the direction of the light source. The “table for the talking head” works in much the same way. The magician, surrounded by mirrors from below, remains invisible to the viewer, except for the part of the body that rises above them. In conditions of complexity of the relief and the shape of the hidden object, it is very difficult to achieve such an effect. But still possible.

Technical specifications

It is known that the "invisibility cloak" is coated with a layer of magnesium fluoride, on which is applied a pattern of tiny gold antenna bricks 30 nanometers thick. This is a very thin film, many times thinner than a hair. The total thickness including the substrate is 50 nanometers. The bricks come in six different sizes, ranging from 30 to 220 nanometers in length and 90 to 175 nm in width. Thanks to these microantennas, it is possible to rotate the mirror surfaces perpendicular to the direction of light and completely scatter it. In this case, both the frequency and the phase of the radiation are taken into account - they are rotated by 180 degrees relative to the initial parameter, which allows it to be fully compensated.

With the right setting of surfaces, polished gold planes can give any effect to the reflected light. It can represent the background of an object (such as a floor) or something completely different. If the invisibility cloak is big enough, it could theoretically cover just about anything. For example, the tank will look like a bicycle. Or it won't be visible at all.

Practical Perspectives

The studies were carried out in the light range with a wavelength of 730 nm (near infrared region of the spectrum). An almost perfect reflection was observed. This scientific achievement is impressive and suggests a new round of the arms race. However, it is too early to think about invisible tanks, missiles, aircraft and other types of deadly equipment. The fact is that the experiments were carried out with a certain object of a complex spatial configuration, with a size of 36 microns in the approximate diameter. If in inches, then this is about one thousandth. In millimeters ... in general, an ordinary grain of sand, only very small. It was she who was wrapped in a mysterious "invisibility cloak". Science is silent about how much it cost to make it optically transparent.

However, someday this invention may be of practical use. For example, cinema screens currently have to be perfectly flat, and in the case of the use of "smart microantenna crystals", this requirement will be unnecessary, and images can be projected onto any curved surfaces without distortion.