Abstract

A laser trapping technique is a powerful tool for manipulating single or plural particle(s). Bums et al. recently demonstrated that lattice structures of latex particles could be created on interference patterns of several laser beams.¹ Also, we showed that particles were aligned in concentric circles or a line image of a single trapping beam, and demonstrated size-selective trapping of particles.² The spatial patterning by these methods is, however, essentially based on the interference, so that there are severe limitations in forming arbitrary patterns. In this paper, we propose a laser scanning micromanipulation technique to produce any spatial patterns of fine particles. The principal key to the technique is repetitive scanning of a focused laser beam by computer-controlled galvano mirrors. If the repetition rate is faster than the time-scale of the Brownian motion, plural particles are trapped along a locus of the scanning spot. In addition to the pattern formation, the trapped particles can be moved continuously along the formed patterns, and the flow velocity is controlled by scanning speed and laser power.

© 1991 Optical Society of America