A material based on "black silicon" could help hide an object's heat signature from infrared sensors, according to a new scientific study by the University of Wisconsin-Madison (UWM).
Published in the journal Advanced Engineering Materials, the research found that the material, which doesn't have a name yet, works via a semiconductor material that's used in modern solar cells to trap light and later convert it into heat or electricity.
This means it could be used as a cloaking material that renders objects, and people, practically invisible to infrared cameras.
UWM professor of electrical and computer engineering, Hongrui Jiang, who led the study, explained that warm objects like human bodies or tank engines emit heat as infrared light but the new material offers substantial improvements over other heat-masking technologies.
"What we have shown is an ultra-thin stealth ‘sheet'," he said. "Right now, what people have is much heavier metal armor or thermal blankets. It's a matter of the weight, the cost and ease of use."
Measuring less than one millimetre thick, the sheet absorbs approximately 94 per cent of the infrared light it encounters. Trapping so much light means that warm objects beneath the cloaking material become almost completely invisible to infrared detectors.
The stealth material can also strongly absorb light in the so-called mid- and long-wavelength infrared range, the type of light emitted by objects at approximately human body temperature. By incorporating electronic heating elements into the stealth sheet, the researchers have also created a high-tech disguise for tricking infrared cameras.
"You can intentionally deceive an infrared detector by presenting a false heat signature," added Jiang. "It could conceal a tank by presenting what looks like a simple highway guardrail."
Black silicon works by absorbing light because it consists of millions of microscopic needles (called nanowires) all pointing upward like a densely-packed forest. Incoming light reflects back and forth between the vertical spires, bouncing around within the material instead of escaping.
Although black silicon has long been known to absorb visible light, Jiang and colleagues were the first to see the material's potential for trapping infrared. They boosted its absorptive properties by tweaking the method through which they created their material.
"We didn't completely reinvent the whole process, but we did extend the process to much taller nanowires," said Jiang.
Jiang and colleagues are working to scale up their prototype for real-world applications with assistance from UWM's Discovery to Product program. They already received a US patent in the fall for the material's use in stealth.
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