Dynamic Self-assembly of Microparticles Electrostatically

Driven in a Poorly Conducting Liquid.*

Maksim V. Sapozhnikov, Yuriy V. Tolmachev, Igor S. Aronson, Wai-Kwong Kwok
Argonne National Laboratory


We performed experimental studies of electrostatically driven granular media (40 and 120 micrometer Bronze particles) immersed in a poorly conducting non-polar liquid (toluene). The conductivity of the liquid was adjusted by adding ethanol (up to 10%). Depending the ethanol concentration and the value of applied DC electric field (up to 20 kV/cm) the microparticles self-assemble into a rich variety of novel phases. These phases include static precipitate (honeycombs and Wigner crystals); and novel dynamic condensate (toroidal vortices and pulsating rings. The discovered asymmetry of the phase diagram with the respect to polarity of the applied voltage is related to the excess of negative ions in the bulk of the liquid when current is present. The observed dynamic phenomena are attributed to interaction between particles and electro-hydrodynamic flows produced by the action of electric field on ionic charges in the bulk of liquid.

* This research is supported by DOE contract #