Exploiting structural (Maxwell-Wagner) polarization effects for the AC-electrokinetic manipulation of objects and media in cell chips

摘要

AC fields induce polarization charges at the structural interfaces inside inhomogeneous media. In suspensions or emulsions of micro and nano objects these structures are introduced by phase boundaries such as biological membranes. Nevertheless, local heating may also introduce "smeared interfaces" into homogeneous electrolytes. Subsequently, the interaction of the polarization charges with the inducing field generates AC-electrokinetic forces. The effects observed depend on the temporal and spatial field properties and the frequency dependence of the dipole moment induced in the objects or volumes. For objects, electroorientation (EO), electrodeformation (ED), dielectrophoresis (DP), electrorotation (ER), field-trapping and travelling wave (TW) DP are well investigated. Heated micro and nano volumes of the medium experience analogous forces which can be used for pumping and mixing, for example. TW pumps and electro-thermal micro-pumps (ETuPs) are well characterized.