Abstract
We study theoretically and numerically the electrokinetic behavior of metal microparticles immersed in aqueous electrolytes. We consider small particles subjected to non-homogeneous ac electric fields and we describe their motion as arising from the combination of electrical forces (dielectrophoresis) and the electroosmotic flows on the particle surface (induced-charge electrophoresis). The net particle motion is known as dipolophoresis. We also study the particle motion induced by travelling electric fields. We find analytical expressions for the dielectrophoresis and induced-charge electrophoresis of metal spheres and we compare them with numerical solutions. This validates our numerical method, which we also use to study the dipolophoresis of metal cylinders.
Highlights
The precise control of small particles in liquid suspension is possible by application of AC electric fields [1,2]
Most theoretical works identify two distinct mechanisms that can lead to motion of a metal particle [27]: (i) the electrical force acting on the induced charges, and the motion induced by this mechanism is known as dielectrophoresis (DEP); and (ii) the particle displacement generated by the induced-charge electroosmostic (ICEO) flows on its surface, which we refer to as induced-charge electrophoresis (ICEP) [38]
The dipolophoretic motion of metal particles subjected to ac fields is described as the combination of two distinct contributions: dielectrophoresis and induced-charge electrophoresis
Summary
The precise control of small particles in liquid suspension is possible by application of AC electric fields [1,2]. The electrokinetics of insulating particles is mainly determined by the intrinsic surface charge that naturally appears at solid-electrolyte interfaces [30] This charge is only slightly perturbed by applied electric fields. The particle displacement when a metal sphere is subjected to a non-homogeneous DC field was first studied by Shilov and Simonova [37] and they coined the term dipolophoresis (DIP) to refer to this phenomenon. Miloh extended this term to the more general case of AC electric fields [25,26]. DIP can be described as the combined effect of DEP and ICEP
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