The optical assembly of nanoparticles

Individual stable atoms and molecules are seldom found far apart unless they are gases. Most matter exists in a condensed phase whose cohesion and integrity are due to fundamental interactions among the particles. The balance between dispersion forces of attraction and short-range electron-cloud repulsions—as in the Lennard-Jones potential—supports the formation of stable equilibrium structures. Remarkably, off-resonant laser radiation can induce additional, optomechanical forces between particles. A publication by Michael Burns and his team1 verified this effect experimentally for a simple system of two identical, spherical particles.