Macroscopic conductivity of tissues from microscopic electrolyte confinement.

A basic model for the electrical properties of biological tissues is to consider them as a collection of cells or other units which, in turn, are composed of electrolyte solutions surrounded by dielectric walls. This presentation discusses the frequency dependence of impedance, conductivity, and permittivity of an aggregate of confined electrolytes as a model for tissues. The model recovers the experimentally observed Debye-type behavior of the permittivity, with peaks at a set of characteristic frequencies. At the microscopic level the electrolyte confinement leads to the appearance of dynamical double layers when subject to oscillating external electric fields. These layers play an important role in the description of the macroscopic properties of tissues at low frequencies.