Electric field induced pattern formation in interfacial metal colloid films

First results on electric field induced aggregation in a novel colloidal film are presented. The aggregate appears as a dark structure on the shiny background of the metallic colloidal film that forms at the interface between two immiscible liquids. A variety of shapes are observed, ranging from compact circular, to highly ramified dendritic ones, depending on control parameters such as voltage and chemical composition. The aggregation process was investigated for a wide range of parameters by video photography and subsequent pattern analysis, as well as by Auger spectroscopic measurements of dried samples. A new type of mechanism-a combination of electroaggregation of the colloid particles and electrodeposition of metal ions-is proposed to account for the observations.