2-D assembly of colloidal particles on a planar electrode

Electrical voltage externally applied between parallel-plate electrodes can cause colloidal particles located near one of the electrodes to aggregate; thus monodisperse particles can be driven to form hexagonally close-packed arrays which can be useful in the fabrication of photonic materials. The mechanism for lateral motion of particles on the electrode surface is electroosmotic flow driven by the action of the applied electric field acting either on the equilibrium charges in the diffuse layer of the particles (ECEO) or on charge induced by the electric field on the surface of the electrode (ICEO). For steady currents, ECEO dominates whereas ICEO dominates for high-frequency alternating current. For intermediate frequencies (10 Hz to 1 kHz) both mechanisms are active. This critical review attempts to integrate concepts from electrochemistry and colloid chemistry to understand this electrokinetic phenomenon.