Matter can be held together by intense light, providing a potentially useful way to craft novel materials, researchers said.
The scientists found they could organize randomly arranged microscopic beads into new structures that lasted as long as they were bathed in the intense light.The practical applications of this observation are still unclear, although experts said it could play a role in devising new methods of optical communications or in arranging molecules to make drugs and other products.
The study was carried out on tiny plastic beads just 1.43 microns, or 0.000057 inch, in diameter. Under the light, they moved toward each other in hops of 0.387 micron, or 0.000015 inch.
"The spheres act like miniature antennas that pick up and then re-radiate light," said Harvard physicist Jene Golovchenko. "This scattered light combines with that coming directly from the laser, giving rise to force fields that bound the small spheres together in space. The length and strength of the bonding are controlled by the intensity and wave length of the laser light."
Golovchenko conducted the research with Michael Burns and Jean-Marc Fournier of the Rowland Institute in Cambridge. It was published recently in Physical Review Letters.
The researchers said that until now, the only known way to bind matter was by atoms exchanging electrons.
The light-assembled structures fall apart as soon as the laser is switched off. However, Golovchenko said that light might be used to align molecules in novel ways, and then they could be made permanent by freezing or chemical processes.
The researchers observed the interaction by putting water-soaked beads between plates of glass and then shining a laser on them.
"The spheres did a kind of dance, hopping between bound states," said Golovchenko, producing an interaction that he believed no one had witnessed before.