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The authors propose and experimentally demonstrate a conveyor-belt method appropriate for building large-scale microparticle structures by sequentially energizing electrodes to aggregate the particles into predetermined locations and then to translate them collectively to a work area for final assembly. This approach employs collective phenomena in a negatively polarized suspension exposed to a high-gradient strong ac electric field. [ABSTRACT FROM AUTHOR]

Experiments were conducted in microfluidics equipped with dielectrophoretic gates arranged perpendicular to the flow. Under the action of a high-gradient ac field and shear, flowing suspensions were found to undergo a phase separation and to form a distinct front between the regions enriched with and depleted of particles. We demonstrate that this many-body phenomenon, which originates from interparticle electrical interactions, provides a method for concentrating particles in focused regions and for separating biological and nonbiological materials. The evolution of the particle patterns formation is well described by a proposed electrohydrodynamic model. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]