Optical rotational self-assembly at air-water surface by a single vortex beam

Abstract

Self-assembly and relevant quantitative measurements of 4 um polystyrene microspheres at air-water surface were realized by utilizing optical tweezers with a low-numerical-aperture (NA) and long-working-distance (WD) microscope objective. It showed that the rotation velocity of a single microsphere varies with a nearly linear dependence on incident laser power with the existence of surface tension at air-water interface. The self-assembly experiments show that the rotation velocity of the bridging particle chain increases clearly as the particle number increases. This work would contribute to the related researches of micro granular structure fabrication and bio-printing of cell tissues. Keywords: Optical rotation dynamics, Optical tweezers, Self-assembly, Orbital angular momentum