Dielectrophoretic interaction of two spherical particles calculated by equivalent multipole-moment method

A generalized equivalent multipole-moment theory is developed for the analysis of the interaction between two spherical dielectric particles in an external field. The method is based on the re-expansion technique: the potential distortion caused by the existence of a dielectric sphere is first expressed as a series of spherical harmonics with r^-n-1 dependence. This potential, having no singularity except at the center of the sphere, is then re-expanded around the center of another sphere as a series of spherical harmonics with rⁿ dependence. Once this re-expansion is done, the effect of neighboring spheres can be incorporated as an externally applied potential, and the field problem can be solved. In this paper, the authors present the principle of the method, together with calculated results for the case of two spherical particles in a uniform external field