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Combined negative dielectrophoresis and phase separation in nondilute suspensions subject to a high-gradient ac electric field

2004; American Physical Society; Volume: 69; Issue: 2 Linguagem: Inglês

10.1103/physreve.69.021402

1550-2376

Anil Kumar, Zhiyong Qiu, Andreas Acrivos, Boris Khusid, David Jacqmin,

Electrowetting and Microfluidic Technologies

Experiments were conducted on concentrated suspensions of neutrally buoyant particles which exhibit negative dielectrophoresis. We found that, due to interparticle electrical interactions, such suspensions undergo a phase separation when subjected to a high-gradient ac field (approximately kV/mm) and form a propagating distinct front between the regions enriched with and depleted of particles. A generalization of our theory for the thermodynamics of the field-induced phase transitions in suspensions of polarized particles [Phys. Rev. E 52, 1669 (1995); 54, 5428 (1996); 60, 3015 (1999)] is proposed for the front propagation, and its predictions are shown to be consistent with the experiments even though the model contains no fitting parameters. The combination of field-induced dielectrophoresis and phase transition provides a method for strongly concentrating particles in prespecified regions of dielectrophoretic devices.