Colloidal hydrodynamic coupling in concentric optical vorticesK. Ladavac1 and D. G. Grier2
1 James Franck Institute and Department of Physics, The University of Chicago Chicago, IL 60637, USA
2 Department of Physics and Center for Soft Matter Research, New York University New York, NY 10003, USA
received 15 February 2005; accepted 31 March 2005
published online 22 April 2005
Optical vortex traps created from helical modes of light can drive fluid-borne colloidal particles in circular trajectories. Concentric circulating rings of particles formed by coaxial optical vortices form a microscopic Couette cell, in which the amount of hydrodynamic drag experienced by the spheres depends on the relative sense of the rings' circulation. Tracking the particles' motions makes possible measurements of the hydrodynamic coupling between the circular particle trains and addresses recently proposed hydrodynamic instabilities for collective colloidal motions on optical vortices.
82.70.Dd - Colloids.
87.80.Cc - Optical trapping.
83.80.Hj - Rheology: Suspensions, dispersions, pastes, slurries, colloids.
© EDP Sciences 2005