Exact treatment of the electrostatic interactions and surface effects in electrorheological fluids

We present exact results for the electrostatic interaction energy and forces in a heterogeneous system containing particles of arbitrary structures placed between two parallel electrode plates at a potential difference. All multipole moments and all multipole images of the particles are included. Our calculations for arrays of coated spherical particles in contact show overwhelming contributions of the multipoles and the image multipoles (dipole approximations may only account for a few percent of the exact forces). The interactions are also greatly affected by small variations in the dielectric constant of the coating.