Light can be used to manipulate and move particles. To the right is a picture of a single layer of micron sized plastic spheres trapped between two closely spaced optical flats. The particles are further confined to horizontal rows of an intensity fringe pattern, produced by crossing two laser beams in the sample. The charge interaction between particles produces an inter-row ordering. In this way a two dimensional crystal structure results (by stimulating the formation of one mode of the crystal with light).
Light Manipulation of Colloidal Particles