Electric field driven phase transition in a confined suspension of negatively polarized particles*

We study the effect of a combination of a strong AC field and a weak DC field on the formation of cellular patterns in suspensions of neutrally-buoyant negatively polarized particles. An unexpected appearance of cellular patterns in such suspensions was observed by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. Following the application of a sufficiently strong AC field, particles aggregated head-to-tail into chains that bridged the gap between two electrodes and then formed a cellular pattern, in which large-scale particle-free domains were enclosed by particle-rich thin walls. These cellular structures were not observed in numerous experiments and MD simulations of field induced phase transitions in polarized suspensions. We will present data on the phase diagram and formation kinetics of cellular patterns by single-particle and multi-particle chains. Depending on applied fields, cellular patterns can be formed in two steps: 2D-> 3D and 3D-> 3D. We also will discuss the design of experiments to study phase transitions in suspensions of non-buoyancy-matched polarized particles in microgravity on the International Space Station.