Zhejiang University Invented "Invisibility Cloak"

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< p > < strong > "miracle" time < /strong > /p >

< p > < strong > pencils, goldfish and cats are all gone. < /strong > < /p >

< p > a cylindrical glass device with six sides. The length is 5 cm and the height is 5 cm. The center of the six edge body is a hole.

Put the right six sides into the pparent fish tank filled with water. Through the six sides, you can see the full view on the other side of the fish tank.

With a pencil passing through the hole in the center of the six sides of the body, something magical happened, and the segment where the pencil was inserted into the hole of the six sides of the body disappeared. Through the glassware, the whole scene on the other side of the fish tank could still be seen as if it were not inserted into the pencil.

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P > a little goldfish swam into the hole of the six side body and suddenly disappeared, and there was no change in the background on the other side of the fish tank.

After a while, the head of the goldfish drilled out of the hole and its body could not be seen.

The goldfish slowly swam out, and its body gradually presented itself to all of us.

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< p > another large hexagonal glass device, squatting a kitten, looking at it from a specific angle, the kitten suddenly disappeared.

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< p > this is a scene in the Department of letters and electronics of Zhejiang University. The two glass device is the latest development of the "a href=" http://sjfzxm.com/news/index_q.asp "stealth dress < /a > by Professor Chen Hongsheng of the International Academy of electromagnetic Sciences, Zhejiang University.

Chen Hongsheng said: "these experiments mean that stealth devices can not only hide objects such as cats and fish, but also can interact with stealth devices. The stealth effect will not be affected."

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< p > < strong > the study of "magic cloak" has been declassified 6 years ago. < /strong > /p >

< p > < strong > actually, 6 years ago, Chen Hongsheng began to study "invisibility cloak".

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< p > 2007, Chen Hongsheng's research on the interaction mechanism between electromagnetic waves and cloaks in collaboration with Massachusetts Institute of Technology in the United States was published in the top physics journal physics review letters.

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< p > the paper first explains the physical mechanism of stealth clothing, and puts forward a theoretical framework for quantitative analysis of < a href= "http://sjfzxm.com/news/index_q.asp" > invisible /a >, which is an important guidance for the design of stealth clothes.

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"P", known as the "global science news network", which is famous for its latest international scientific research achievements, takes the scientific explanation of the physical mechanism behind the stealth clothes as the headline. It has reported the research results in detail and has made an exclusive interview with Chen Hongsheng.

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< p > < strong > principle allows the light to bypass the stone like a stream. < /strong > /p >

< p > strong > to make objects invisible, we must first understand why objects can be seen.

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< p > according to the introduction of the "electromagnetic stealth mechanism and experimental research" project team, when electromagnetic waves are irradiated on objects, they will scatter on objects.

When the scattered electromagnetic wave is received by the human eye and so on, the object can be found there.

"The stealth technology applied in reality at present, such as stealth aircraft, mainly absorbs radar electromagnetic waves, so that the reflected electromagnetic wave is minimal or equal to zero, so that radar can not feel it, but this technology is not a real stealth."

Chen Hongsheng said.

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< p > 2006, John Pendy, of Imperial College London in the United Kingdom, published an article in the journal Science. It proposed the use of coordinate pformation to design invisibility cloak, which neither reflected nor absorbed electromagnetic waves, but allowed electromagnetic waves to bypass the stealthy areas and propagate according to the original direction, so that objects could be completely invisible.

This is the "hall level" theory of stealth design, which lays a theoretical foundation for the research of stealthy clothes.

Its core idea is to change the refractive index of the surface of the material, so that the light can be turned around and the object will be hidden in the original direction.

"There is a stone in the stream. The stream will diverge before the stone, and then close it up and then close it up, as if it had never met a stone."

The research team of Zhejiang University needs to make light flow around the stone like a stream.

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< p > < strong > practical design of polygonal invisibility cloak in visible light band < /strong > /p >

< p > < strong > theory is available, but it is not easy to make a camouflage garment.

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In the past two years, Chen Hongsheng's research team has focused on how to stealth objects in visible light, that is to say, how to make objects invisible in the eyes of P.

They further simplified the theoretical system proposed by Peng Delhi, and put forward a design method of polygonal stealth clothing in visible light band. By means of uniform linear pformation, the parameters of each part of stealth clothing were designed and simplified, so that the stealth clothing became practical from theory.

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< p > "the human eye is not sensitive to the light phase and the slight delay."

In combination with this characteristic, the research team eliminated the condition of "keeping the same phase of light" in the theory of Peng Delhi. "In this way, stealth devices can use more easily available materials, and do not need nano scale process to cut down the difficulty of design and implementation of stealth clothes."

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< p > 2012, Chen Hongsheng research team developed a set of columnar < a href= "http://sjfzxm.com/news/index_q.asp" > stealth device < /a > by using a birefringent crystal which existed in nature.

"But the scale of this material is very small, and it can only be invisible to a polarized light, and it can not be prepared on a large scale."

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< p > 2013, through further theoretical analysis, the research team optimized the parameters of stealth devices, and selected a glass which could be prepared in large scale in industry as the material of stealth clothing, and enlarged the "size" of the stealth garment to the diameter of more than 100 meters, and it could stealth in any polarized natural light.

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< p > < strong > application prospect < /strong > < /p >

< p > < strong > achieving real stealth is still very difficult at present, < /strong > /p >

< p > PENG Delhi saw the progress of Zhejiang University. He said this is a real progress in the field of invisibility cloak research.

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At present, the "stealth garment" of Zhejiang University is still very elementary. Only when the hexagon stealth device looks at the direction of the six edges and corners, can it have a good stealth effect. P

In addition, "invisibility cloak" itself can not be invisible.

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< p > according to the introduction, there are two categories of research on stealth devices: one is the carpet stealth device, the object is hidden under the carpet stealth device. For the observers above, the effect is like that of a smooth ground.

The second category is the Harry Potter stealth garment, which is usually understood, which can move away from the ground.

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< p > from the perspective of application, stealthy clothing must be able to work in broadband, omnidirectional and full polarization if it can be applied well. It is very difficult to achieve this ultimate goal.

"The mechanism and experimental research of electromagnetic camouflage" project team said that to realize the ideal of "perfect stealth" of Peng De, it is very difficult to make a real invisibility cloak on the body.

Because of the technical bottlenecks of material parameters such as harsh and inconvenient, the research of stealth clothing is still at the stage of experimental verification and testing. There is still a long way to go before the application. However, the team is confident that electromagnetic wave stealth will be a major opportunity for stealth technology to enter the life field.

Although there are still some limitations in the current technology, we have reason to believe that the dream of human invisibility will eventually come true.

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