WHEN LIKE CHARGES ATTRACT - THE EFFECTS OF GEOMETRICAL CONFINEMENT ONLONG-RANGE COLLOIDAL INTERACTIONS

High-resolution measurements of the interaction potential between pair s of charged colloidal microspheres suspended in water provide stringe nt tests for theories of colloidal interactions, The screened Coulomb repulsions we observe for isolated spheres agree quantitatively with p redictions of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Conf ining the same spheres between charged glass walls, however, induces a strong long-range attractive interaction which is not accounted for b y the DLVO theory.