Quick Change Stuff

Quick Change Stuff

What if soldiers' uniforms repaired rips or tears on their own? And those uniforms could change color to blend in anywhere? As this ScienCentral News video reports, some nanotechnologists are working on smart stuff that could fix itself or change color for protection – the way living things do.

Smart Stuff
If current nanotechnology research is successful, military uniforms of the future might bring new meaning to the word "camouflage" – they could be able to repair themselves and change color when soldiers really need to blend in.

"You could think of something like a camouflage-type material that could respond based on the overall light input from the surrounding environment," says George Bachand, a molecular biologist at Sandia National Laboratories. Bachand is working to make new "smart" materials that could do some of the things living things do, such as heal breaks and wounds, or change color or shape for protection in response to what's going on around them.

A major difference between living and synthetic (man-made) materials is that living things are capable of adapting to a changing environment, while synthetic systems cannot. "Living materials are capable of doing things such as self-healing, or being able to reconfigure (change) their overall structure, color, or properties, based on the cells' needs, as opposed to synthetic (man-made) materials," says Bachand. "Once you form them, there they are, and that's pretty much what you're going to get. What we're trying to mimic is the ability of some living organisms" – including some fish and other marine creatures such as octopi and squid – "to change color in response to changing light conditions."

When light hits a fish, nanoparticles on the fish's skin will change their spacing and distribution. Therefore, the optical (visual) properties of the surface will change, so that the fish's skin will change color. "We're trying to do the same thing, but in a synthetic (man-made) system," says Bachand.

To make such new materials, Bachand has to find ways to get living and synthetic molecules to work together. He starts with living molecules that look like curling ribbons. They transport small molecules and other material inside cells. "These living molecules are capable of hauling around cargo and bringing it to a very precise location," explains Bachand. Once they reach their destination in a cell, living molecules also are able to carry out repairs.

Quantum dots under UV light, glowing in different colors.

Bachand's living molecules can carry very tiny crystals each about the size of a molecule. Made of semi-conducting materials, the tiny crystals can give off neon-bright colors; the color depends on each particle's size. Since changing the distance between the crystals can change the colors they emit, moving them closer together or farther apart could change a synthetic (man-made) surface's color, the same way a fish changes its skin color. That means that if Bachand's molecules work, soldiers of the future could be wearing uniforms that change color and mend themselves.

This research was presented at the Defense Advanced Research Projects Agency (DARPA) Biomolecular Motors Workshop in 2003 and appeared in Nature Materials in 2002. It was funded by DARPA and the U.S. Department of Energy (DOE).

by Karen Lurie