Authors: J. Gimsa, M. Stubbe
Affilation: University of Rostock, Germany
Pages: 293 - 296
Keywords: AC-electrokinetics, Maxwell-Wagner polarization, combined effects
AC fields induce polarization charges at the structural interfaces inside inhomogeneous media (Maxwell-Wagner polarization). In suspensions or emulsions of micro and nano objects such as particles, oil droplets, air bubbles and biological cells, these structures are introduced by the boundaries of media like biological membranes. Nevertheless, local heating may introduce “smeared interfaces” also into homogeneous bulk media, e.g. aqueous electrolytes. In all these cases, the interaction of the polarization charges with the inducing field generates forces which are the basis for AC-electrokinetic effects. The observed effect depends on the temporal and spatial field properties. The frequency dependence of the dipole moment induced in the objects or volumes generates particular frequency spectra. For objects, electroorientation (EO), electrodeformation (ED), dielectrophoresis (DP), electrorotation (ER), field-trapping/caging and travelling wave (TW) DP are well investigated. Nevertheless, heated micro and nano volumes of the medium experience analogous forces which can be used e.g. for pumping and mixing. TW pumps and electro-thermal micro-pumps (ETµPs) are well characterized.