On the aggregation kinetics of two particles trapped in an optical tweezers

Two suspended particles trapped in an optical tweezers will collide with each other in a confined volume. This characteristic has been successfully used to study the stability of a dispersion at the individual particle level. In this paper, we present a phenomenological theory to describe the aggregation kinetics of the two trapped particles. The experimental results are analyzed applying the theory. The analysis shows that the statuses of two particles undergo two stages, "compact status" and "relaxed status", after they are trapped into the optical tweezers. The time in the compact status is very short and the two particles collide once in the compact status. Then the status of two particles transforms to the relaxed status, in which the two particles collide with each other at a constant and low frequency. It gives a clear understanding of the aggregation kinetics of two particles trapped in optical tweezers. Based on the formulation, different approximate formulas have been deduced to get the stability ratio from the microscopic experimental results. (c) 2005 Elsevier B.V. All rights reserved.