A dual-beam dynamic light-scattering arrangement is devised to measure the time-dependent mean squared relative displacement of a pair of tracer particles with a small separation of micrometers. The technique is tested by the measurement of the relative diffusion of polymer latex spheres suspended in a simple viscous fluid. The experiment verifies the theory and demonstrates its applications. The dual-beam dynamic light-scattering technique, when combined with an optical microscope, provides a powerful tool for the study of two-particle microrheology of soft materials. The advantages of the new technique are its high statistical accuracy, faster temporal response, and ease of use.
© 2004 Optical Society of America
Xin-Liang Qiu, Penger Tong, and Bruce J. Ackerson, "Proposal and Testing of Dual-Beam Dynamic Light Scattering for Two-Particle Microrheology," Appl. Opt. 43, 3382-3390 (2004)