Two-dimensional electrohydrodynamically induced colloidal phases

Over the past decade, experiments have shown that applied electric fields can be used to assemble colloids at electrode surfaces via an apparently electrohydrodynamic attractive interaction. Recently however, it has been seen that confinement strongly influences this process, simultaneously suppressing the apparent attractions while increasing the relative importance of field-induced dipole-dipole repulsions. By varying the degree of confinement and the strength of the applied field, one can alter the relative magnitude of these competing effects. We show here that one can take advantage of this interplay for the construction of novel two-dimensional colloidal phases.