  We study the effective interaction between a planar array of uniformly
negatively charged, stiff rods parallel to a negatively charged planar
substrate in the absence of salt in a continuous, isotropic dielectric medium.
Using Brownian dynamics simulations, we examine the general effects of
counterion valence, rod spacing, macroion charge densities, and the rod size on
the attractive rod-surface interaction force. At room temperature divalent as
well as monovalent counterions mediate an interaction that can be repulsive or
attractive upon adjusting either the macroion charge densities or the rod
radius. Finally, we examine the effects of discretizing the surface charge as
laterally mobile monovalent anions and of electrostatic images in the
substrate.
