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The metamaterials that cover people and objects from radar, visible light or infrared are usually thick and heavy, but engineers at the University of Wisconsin-Madison have developed an ultra-thin sheet and light that absorbs thermal signatures.
The stealth sheet measures less than one millimeter in thickness and can absorb about 94 percent of the infrared light that strikes it, including the range of medium and long wavelengths generally released by heat. of the human body. This makes it efficient, lightweight and – thanks to the materials it is made of – relatively inexpensive.
"What we have shown is an ultra-thin" stealth sheet ", says Hongrui Jiang, senior researcher on the project. "At the present time, what people have, it's a metal armor or much heavier thermal blankets, it's a matter of weight, cost and ease of use." use.
The stealth sheet owes its infrared invisibility to the material of which it is made: black silicon. This substance consists of millions of vertical silicon nanowires that trap light between them, forming one of the most effective light-absorbing materials ever created. Black silicon is often used to improve the efficiency of solar panels, while a similar material, Vantablack, works on the same principle but uses carbon nanowires.
Normally, black silicon works on visible light, but researchers have suspected that it could be adapted to absorb the infrared instead. To do this, they used silver particles to etch silicon in nanowires larger than usual, which helped to increase the infrared absorption rate of the material. The silicon nanowire is then attached to a flexible backing that is made with air channels to help release the trapped heat and keep the mantle working longer.
To add some deception, the team added electronic heating elements to the sheet. This allows the stealthy sheet to look like a completely different object when viewed through an infrared camera.
"You can intentionally mislead an infrared detector by presenting a false thermal signature," says Jiang. "It could hide a tank by presenting what looks like a simple highway slide."
The researchers are currently working on scaling up the prototype, before testing it in the real world.
The research was published in the journal Advanced engineering materials.
Source: University of Wisconsin-Madison
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