Electric-field-induced polarization and interactions of uncharged colloids in salt solutions.

The electric-field-induced charge distribution and potential around a colloidal sphere and rod in salt solutions are analyzed. The resulting field-induced colloid-colloid interactions are calculated for specific orientations. The colloids are assumed to be uncharged (or very weakly charged), such that the deflection of ion fluxes by the cores of the colloids is the dominant polarization mechanism (which is referred to as volume-polarization). Explicit expressions are derived for the frequency-dependent charge distribution and the potential in case of a symmetric electrolyte. It is shown that colloid-colloid interactions due to the induced charge distributions can be much larger than the thermal energy, and are therefore sufficiently strong to give rise to electric-field-induced phase transitions. The present study is a first step towards a quantitative description of field-induced transitions for systems where volume-polarization is the dominant polarization mechanism.