Mythical object of the Harry Potter saga, the invisibility cloak fascinates and sometimes, we would like to slip under it. But, by the way, would it be possible to become invisible?
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[EN VIDÉO] Become invisible through contact lenses, with the Rochester Cloak The dream of invisibility stirs the imagination of scientists, as evidenced by this pretty technical trick carried out by researchers at the University of Rochester. Using simple lenses, these scientists were able to deflect light to create a ring of invisibility. The experience can be seen here on video.
Failing to recover the cape of Harry Potter itself, many solutions have been sought by scientists to try to reproduce this object which offers great opportunities for camouflage.
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The Shield of Invisibility
This shield is made from lenticular lenses. This material is dense enough to slow down light and change the direction of its rays, which is called refraction. In this case, the shield deflects the trajectory of light around the object it hides. So, while hiding behind it, a person standing in front of the invisibility shield will just feel like they are looking at a piece of plastic in front of a wall slightly blurred, but we will not guess the presence of anything behind.
However, the shield only renders invisible if placed in the same orientation as the subject. For example, both horizontally. Otherwise, the object or person behind the shield will still be visible. That said, if the goal is to reproduce a cape, you should know that this technique, as efficient as it is, does not apply to fabric.
The Invisibility Barrier
There is also another method with a shield which could be declined in invisibility cloak. It is a barrier that would have the ability to deflect light rays, so that they curve enough to avoid the protected object. This would allow the light not to reach the object, so that it is totally invisible. For this, it would take metamaterials made up of reflective nano-antennae. Metamaterials, artificial composites, are formed from several layers of a fiberglass matrix, stacked on top of each other and between which are inserted metal rings. Here, the metamaterials used consist of reflective nano-antennae. These will be used to scatter the light waves so that the object below is completely invisible. A promising technology, but which remains expensive to achieve.
The octopus technique
This method would certainly be the easiest to perform. Here, the idea would rather be the camouflageas octopuses. These use their chromatophorescells pigmentary of the skin that allow them to render themselves almost undetectable. By contracting their muscles, the distribution of pigment varies in the cells, and this is what leads to a change of color. Based on this principle, researchers have attempted to develop artificial skin based on electro-active elastomer. It is a material whose texture and the fluorescence vary when an electric field is applied to it. This method allows you to change color quickly to camouflage yourself. This does not actually make invisible but this method allows at least effective camouflage.
The New Zealand Spiny Stick Insect The thorny stick insect (Acanthoxyla prasina) lives mainly in New Zealand. It has prickly skin resembling the branches of the plants it eats. The species reproduces in a single-parent mode called parthenogenesis: the female produces the eggs without the help of the male. To date, no male spiny stick insects have been found. Origin: New Zealand. © Alan Gilchrist, Wikimedia Commons, CC by-sa 3.0
The Rossi stick insect or devil’s stick, a stick insect from France The Rossi stick insect (Bacillus rossius), or devil’s stick, is present in the Mediterranean basin, where the climate is dry. It is the rarest of the three species of stick insects living in France. Its body color varies from light green to brown. Origin: Mediterranean basin (Spain, France, Italy, Balkans). © Lucarelli, Wikimedia Commons, CC by-sa 3.0
One of the largest stick insects in the world, Heteropteryx dilatata With a size of up to 15 cm, Heteropteryx dilatata is one of the largest stick insect species in the world. The animal lives in humid forests, mainly in Malaysia. It uses its very spiny hind legs to ram a possible predator. It can also play dead for several tens of minutes. Origin: Malaysia. © Josh More, Flickr, CC by-nc-nd 2.0
The scorpion stick insect The stick insect Extatosoma tiaratum, also called the tiara stick insect, often puts itself in a posture resembling that of a scorpion when it feels in danger. For this reason, it is also often called the scorpion stick insect. Origin: Australia. © Stephan M. Höhne, Wikimedia Commons, CC by-sa 3.0
The invisible stick insect, an incredible mimicry Stick insects blend in wonderfully with their environment, this is called mimicry. Even photographers are taken in: the one behind this image thought he was photographing a simple branch of thyme before realizing that it was actually an insect! © Gerard Joyon, Wikimedia Commons, CC by 3.0
The stick insect Extatosoma tiaratum, a fragile species Extatosoma tiaratum is a stick insect species that is very sensitive to inbreeding problems. In breeding, it is therefore necessary to make frequent crossings of strains in order to avoid a rapid degeneration of the individuals. Origin: Australia. © Paul Allais, Flickr, CC by-nc-sa 2.0
The Peruvian stick insect, a non-mimetic stick insect Unlike most stick insects, the Peru stick insect (Oreophoetes peruana) has no mimicry with its environment, the females being black and the males bright red. To protect themselves, these insects secrete a whitish liquid whose smell repels predators. Origin: Peru. © Vogelfoto69, Flickr, CC by-nc-nd 2.0
The Australian Tiara stick insect The male tiara stick insect (Extatosoma tiaratum) lives about 5 months, and the female 8 to 12 months. Both moult several times during growth. When the animal feels threatened, it takes on the appearance of a scorpion by curving its abdomen. Origin: Australia. © Dominique Vernier, Fotolia
A stick insect from Australia, Extatosoma tiaratum Extatosoma tiaratum can feed on a variety of foods. However, this stick insect particularly likes brambles, eucalyptus, oaks and roses. Origin: Australia. © Stephan M. Höhne, Wikimedia Commons, CC by-sa 3.0
Malaysian giant phyllia The giant phyllia (Phyllium giganteum) is a leaf stick insect that measures approximately 12 cm. It reproduces mainly by parthenogenesis, a phenomenon by which the female produces the eggs without the help of a male. Although the presence of males is confirmed in the natural environment, it is exceptional in breeding. Origin: Malaysia. © bathyporeia, Flickr, CC by-nc-nd 2.0
Black stick insect Peruphasma schultei mating Unlike most stick insects, Peruphasma schultei has a black color. As adults, stick insects of this species develop small, bright red wings that they spread to scare away predators. If that’s not enough, they can secrete a poisonous fluid called peruphasmal. Matings are frequent and can last several days. Origin: Peru. © Luc Viatour, Wikimedia Commons, CC by-sa 3.0
The leaf stick insect Extatosome tiaratum Extatosome tiaratum is a “leaf” type stick insect, as they have leaf-like legs and bodies. © Simon Egan, Wikimedia Commons, CC by-sa 3.0
The Peruvian stick insect, Oreophoetes peruana As its name suggests, the Peruvian stick insect (Oreophoetes peruana) lives in the country of the same name. It lives at high altitude, sometimes over 2,000 m, and feeds only on ferns. Origin: Peru. © Drägüs, Wikimedia Commons, CC by-sa 3.0
Stick insects, camouflage experts These images attest to the fabulous mimicry abilities of stick insects. © David Midgley, Flickr, CC by-nc 2.0 © Marc AuMarc, Flickr, CC by-nc 2.0
The survival of stick insects Stick insects can adopt different techniques to survive in their environment. While some species have become experts in the art of camouflage, others remain immobile for several hours; still others secrete toxic substances. © Ferran Pestaña, Flickr, CC by-sa 2.0
The stick insect, an amazing insect Stick insects can take various forms, generally adapting to the environment in which they evolve. The one in the picture looks like a green twig and can easily be confused with the plant it is feeding on. © Josh More, Flickr, CC by-nc-nd 2.0
A Malaysian leaf stick insect Giant phyllia (Phyllium giganteum) is a leaf stick insect native to Malaysia. It looks like a gnawed guava leaf, the plant on which it feeds in nature. Origin: Malaysia. © Paul Allais, Flickr, CC by-nc-sa 2.0
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