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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 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 their overall structure, color, or properties, based on the cells' physiology and the cells' needs, as opposed to synthetic materials, which are just static in nature," 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 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 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, called motor proteins. They transport small molecules and other material inside cells. "These motor proteins are capable of hauling around cargo and bringing it to a very precise location," explains Bachand. Once they reach their destination in a cell, motor proteins also are able to carry out repairs.
So far, Bachand's motor proteins have been able to deliver nanoscale particles of gold – each one the size of a few atoms. The next steps, says Bachand, are "to take those materials, those nanoparticles, and assemble them in a very directed fashion. We'd be able to take these gold nanoparticles and string them in a way that would be analogous to stringing beads together, and form some kind of a gold wire" that could help make repairs.
Quantum dots under UV light, glowing in different colors.
Bachand's motor proteins can also carry very tiny crystals called quantum dots, each about the size of a molecule. Made of semi-conducting materials, quantum dots can give off neon-bright colors; the color depends on each particle's size. Since changing the distance between quantum dots of different sizes can change the colors they emit, moving them closer together or farther apart could change a synthetic surface's color, the same way a fish changes its skin color. That means that if Bachand's proteins work, soldiers of the future could be wearing uniforms that change color and mend themselves.
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