When like charges attract: interactions and dynamics in charge-stabilized colloidal suspensions

Measured pair interactions among highly charged colloidal spheres dispersed in simple electrolytes yield several surprises. Isolated pairs of like-cha rged spheres are found to repel each other, much as predicted by convention al theory. The same spheres, however, can develop a strong and long-ranged attraction for each other when confined either by charged glass walls, or b y neighbouring spheres. Such like-charge attractions are inconsistent with the mean-field theory for macroionic interactions. These and other experime ntal observations further constrain recently proposed extensions to the mea n-field theory.