Illustration: Alan Stonebraker

Figure 1: The cartoon at left shows how the motion of particles can become arrested in a colloidal dispersion. The caging mechanism occurs in concentrated dispersions: a reference particle (red) is hindered from moving by excluded volume interactions with its neighbors (blue), that are in turn are hindered by their neighbors (grey). Caging effects can make the response of the colloidal dispersion to a time varying shear force ($γ·$) highly nonlinear. The image on the right shows a simulation of how the microstructure is distorted in the plane of shear for a concentrated hard sphere dispersion under shear flow at a relatively moderate shear rate (see [11]) [Courtesy of J. F. Brady, CalTech]