The result is that pure aluminum looks like gold, and the appearance is literally skin deep."I cannot tell it's not gold," Dr. Guo said. "It looks very pretty."
...
The laser bursts -- each lasting only about 60 millionths of a billionth of a second -- melt and vaporize metal atoms near the surface, which then reassemble in minuscule structures including pits, spheres and rods that are a fraction of a millionth of a meter in size.
By changing the length, strength and number of pulses, the researchers found they could vary the resulting color.
In some cases, the change causes the structures to absorb a range of colors so that they cannot be seen. But the colors that are not absorbed are still reflected, and thus visible, resulting in gold aluminum or dark blue tungsten.
That's some clever stuff. Not quite programmable matter, but still pretty cool.
At the very least, there are probably some applications in building surfaces with carefully tuned absorption bands. I'm also wondering if you could build optical metamaterials with similar techniques...
I do have to wonder about its actual long-term durability, however. After ten years of being rubbed, for instance, I wonder if a ring will retain its color.
Or you can just read the press release at http://www.rochester.edu/news/show.php?id=3106