UWM black silicon material in action

Scientists from the University of Wisconsin-Madison (UWM) have developed a new type of material that can hide an object's heat signature from infrared sensors.

The new material doesn't have a name yet, but it's based on so-called "black silicon," a semiconductor material that's used in modern solar cells to trap light and later convert it into heat or electricity.

New material traps around 94% of infrared light

But while black silicon can trap some infrared light, it does not trap most of it. The UWM research team modified standard black silicon to work better at catching roughly 94 percent of the infrared light that hits its surface.

This keeps infrared light reflecting from other objects from passing through the researchers' black silicon material.

The result is a one millimeter wide —roughly the thickness of 10 paper pages— thin sheet that can be placed over objects and even the human body to shield infrared light being reflected away and picked up by infrared scans.

New material = black silicon + silver

Researchers created this new black silicon material by modifying the material's surface.

By default, black silicon absorbs light because it consists of millions of microscopic needles (called nanowires) that point upward like a densely-packed forest. Light enters these nanowires and reflects back and forth between the vertical spires, bouncing around within the material instead of reflecting off.

Black silicon
Black silicon [Source: Wikimedia Commons]

The UWM team modified the structure and height of black silicon's nanowires.

"We didn't completely reinvent the whole process, but we did extend the process to much taller nanowires," says UWM Professor Hongrui Jiang.

Besides making the nanowires taller, they also added silver, a material that helps absorb light in the infrared spectrum.

Optimal for military applications

The new material is still under development, and its applicability will rely on the ability to mass-produce it.

"It's a matter of the weight, the cost and ease of use," says Jiang. "

The material's applicability is pretty obvious —the military— where it could be used as infrared shielding for humans and weapons and prevent infrared-based heat signature sensors from picking up troop movements.

"You can intentionally deceive an infrared detector by presenting a false heat signature," says Jiang. "It could conceal a tank by presenting what looks like a simple highway guardrail."

More details are available in the research team's paper, titled "Broadband and Ultrathin Infrared Stealth Sheets."