Using optical tweezers, we measure the anisotropic hydrodynamic mobility of a colloidal particle by tracking its thermal motion in an optical trap located near fluid-fluid interfaces, namely, liquid-vapor and liquid-liquid interfaces. The method requires no controlled fluid flow, is independent of conservative interactions between particle and interface, and resolves distance dependent friction to within a fraction of the particle radius. Near the liquid-vapor interface, the friction decreases below that in the bulk, corresponding to predictions of a “perfect-slip” surface.
Wednesday, December 9, 2009
Hydrodynamic Mobility of an Optically Trapped Colloidal Particle near Fluid-Fluid Interfaces
G. M. Wang, R. Prabhakar, and E. M. Sevick
Using optical tweezers, we measure the anisotropic hydrodynamic mobility of a colloidal particle by tracking its thermal motion in an optical trap located near fluid-fluid interfaces, namely, liquid-vapor and liquid-liquid interfaces. The method requires no controlled fluid flow, is independent of conservative interactions between particle and interface, and resolves distance dependent friction to within a fraction of the particle radius. Near the liquid-vapor interface, the friction decreases below that in the bulk, corresponding to predictions of a “perfect-slip” surface.
Using optical tweezers, we measure the anisotropic hydrodynamic mobility of a colloidal particle by tracking its thermal motion in an optical trap located near fluid-fluid interfaces, namely, liquid-vapor and liquid-liquid interfaces. The method requires no controlled fluid flow, is independent of conservative interactions between particle and interface, and resolves distance dependent friction to within a fraction of the particle radius. Near the liquid-vapor interface, the friction decreases below that in the bulk, corresponding to predictions of a “perfect-slip” surface.
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