Impedance based methods for cell characterization and modeling

Common impedance methods in tissues or cell suspensions as well as dielectric particle spectroscopy by ACelectrokinetics are based on the impedance properties of the different constituents of tissue, particles or cells and the suspensionmedia.Whereas impedancemethods detect the frequency dependence of the direct electric response of a suspension, electrokinetic methods investigate the frequency dependence of orientation, deformation, movement, aggregation or rotation of single objects. The latter effects arise from the interaction of the induced polarization of the objects with the inducing external field. Unlike impedance, AC-electrokinetics requires a sufficiently high field strength (>1000 V/m) and the (microscopic) observability of the induced movements. Their advantage is the higher parameter resolution and the discrimination against electrode property effects. Whereas impedance methods are integrative, AC-electrokinetic methods are differential, i.e. impedance determines the integral polarizability of external medium and the objects, while AC-electrokinetics is based on the difference in the polarizabilities. Nevertheless, in both approaches analytical descriptions are based on the same structured geometrical models, e.g. multi-shell ellipsoidal cell models.