Attraction between like-charge particles

The existence of long-range electrostatic attraction between particles with like charge is one of the great current controversies of colloidal science. The classical DLVO theory predicts that an isolated pair of like-charged colloidal spheres in electrolyte should experience a purely repulsive Coulombic interaction. Direct measurements of such interactions have shown excellent agreement with DLVO theory. Recent experiments, however, provide evidence that the effective interparticle potential show a long-range attraction under certain conditions. A satisfactory theoretical explanation for this behavior has proven elusive. There are even some doubts about its origin. Further experimental and theoretical investigations of this surprising phenomenon could be very rewarding.