Electric field driven aggregation of negatively and positively polarized particles in dilute suspensions*

We will present data on the electric field driven particle aggregation in dilute suspensions of nearly neutrally-buoyant negatively and positively polarized particles. Following the application of a sufficiently strong high-frequency AC field to both suspensions, particles aggregated head-to-tail into chains that bridged the gap between two electrodes. Once a weak DC field was added, negatively polarized particles formed a cellular pattern, in which large-scale particle-free domains were enclosed by particle-rich thin walls. The appearance of such patterns in suspensions of negatively polarized particles in a strong AC field was observed by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. However, formation of cellular structures is not predicted by current theories for the field induced particle aggregation in polarized suspensions.