Related Experiment Video
Updated: Feb 21, 2026

Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures
Published on: May 20, 2014
Decoupling of translational and rotational diffusion in quasi-2D colloidal fluids
1Department of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Abstract:
We observe the translational and rotational diffusion of dimer tracer particles in quasi-2D colloidal samples. The dimers are in dense samples of two different sizes of spherical colloidal particles, with the area fraction ϕ of the particles varying from dilute to nearly glassy. At low ϕ, rotational and translational diffusion have a ratio set by the dimer size, as expected. At higher ϕ, dimers become caged by their neighboring particles, and both rotational and translational diffusion become slow. For short dimers, we observe rapid reorientations so that the rotational diffusion is faster than the translational diffusion: the two modes of diffusion are decoupled and have different ϕ dependence. Longer dimers do not exhibit fast rotations, and we find that their translational and rotational diffusion stay coupled for all ϕ. Our results bridge prior results that used spheres (very fast rotation) and long ellipsoids (very slow rotation).
More Related Videos
Related Concept Videos
Colloids and Suspensions
Protein Diffusion in the Membrane
Couette Flow
Colloids
The Fluid Mosaic Model
Colloidal precipitates

