Effect of electrode geometry on the impedance evaluation of tissue and cell culture

This paper explores the effect of electrode geometry on bio-impedance measurements of a simple binary electrolyte (KCl), conductive gel used in electrocardiography (ECG), human umbilical vein endothelial cell (HUVEC) culture and excised human skin tissue. The aim of this paper is (a) to understand the effect of electrode area on the impedance characteristics of various biologically relevant materials and (b) to determine the optimum microelectrode geometry for effective characterization of the electrical properties of these materials, namely, complex conductivity and permittivity. Impedance measurements were performed on four different electrode geometries in the frequency range of 100 Hz to 100 MHz. Four different materials listed above were evaluated on identical sets of electrodes. Results indicate a material-dependent lower limit of 100-50 mu m electrode diameter beyond which non-uniform current distribution effects are noticeable. The skin tissue does not lend itself well to characterization using microelectrodes less than 250 mu m, due to its high degree of heterogeneity. (c) 2007 Elsevier B.V. All rights reserved.