Today’s soldiers are armed with so many high-tech gadgets that they’re advertised as “an army of one.”

Now, as this ScienCentral news video reports, it looks like one of those high-tech devices may be the uniform itself.

Color Wars

On the battlefield or on patrol, soldiers risk being separated from their own troops. They need a way to distinguish their side from the enemy. So scientists at the Massachusetts Institute of Technology’s (MIT) Institute for Soldier Nanotechnologies (in partnership with the U.S. Army) set out to create a fabric that carried an optical bar code, visible only to someone wearing special goggles.

Yoel Fink, assistant professor of materials science at MIT, specializes in inventing new materials. In 1998, he and his colleagues created what he calls a "perfect mirror," capable of reflecting any and all light that strikes it, from any direction. This mirror doesn't look like a mirror at all. Unlike conventional mirrors, it is a flat metallic gray. Seen through infrared goggles, however, it is extraordinarily reflective, giving off a portion of the light spectrum that is invisible to our unaided eyes. Fink wanted to create a fiber made of these powerful mirrors, but in order to do so the mirrors would have to be reduced in size to the width of a human hair. This is the realm of nanotechnology.

Nanotechnologists are scientists who manipulate structures at microscopic levels, in order to obtain new and extraordinary properties. Some nanotechnologists start at nanoscale, or the atomic level. (A nanometer is hundreds of times less than the width of a human hair.) Others work to reduce large materials to nanoscale. To fashion his perfect mirror into mirror fiber, Fink needed a special process that would shrink the layers enormously, without destroying their arrangement and retain their high reflectivity.

The mirrors are made of glass and plastic. Both have very different optical properties: light travels more quickly through the plastic. But these two materials react in the same way to heat—they flow together when heated to a particular temperature.

One of Fink’s students, Shandon Hart, and his co-workers at MIT's Department of Materials Science, constructed a cylinder made of thick, alternating layers of the two materials. They fed the cylinder into a tall, narrow lab furnace, called a draw tower. In the heat, the cylinder thins out drastically and stretches into a long, slim fiber. Inside it, the layers remain intact while shrinking in thickness. Along the way they become strongly reflective. The entire process is controlled by a laser-thickness measuring device, which allows the user to set the final layer thickness at will.

Next, Fink and his students will transform the mirror fiber into thread that can be woven into fabric. The U.S. Army is interested in weaving Fink's thread into uniforms to produce a special colored signature. Visible only to our soldiers, it would help them recognize each other, even through smoke, fog, or darkness.