Chain Structures of Microparticles Induced by Focusing a Laser Beam near the Liquid‐Air Interface of a Droplet

We investigate optically induced dynamics of micron‐sized particles by focusing a laser beam near the liquid‐air interface of a suspension droplet. We find three distinct regimes in behaviors of particles depending on the contact angle of the droplet: convection, linear flow and formation of a closed‐packed array. These behaviors are governed by the most dominant of effects arising from a focused laser beam, such as local heating and radiation pressure. We find that micron‐sized polystyrene beads can be assembled into a chain structure by taking advantage of linear flows. This novel method is applicable to the formation of a chain of carbon nanotubes, non‐transparent objects which are difficult to trap.