Combined negative dielectrophoresis and phase separation in nondilute suspensions subject to a high-gradient ac electric field.
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.
The Levich Institute, The City College of New York, 140th Street & Convent Avenue, New York, New York 10031, USA. anil@levdec.engr.ccny.cuny.edu
Anil
A
Kumar
Zhiyong
Z
Qiu
Andreas
A
Acrivos
Boris
B
Khusid
David
D
Jacqmin