Fig. 3

Four- (a) and two- (b) electrode systems illustrated with two possible cell models (b). a The model of the impedance measurement system with four electrodes (E1, E2, E3, and E4). b An adherent cell partially on top of E2 and a non-adherent cell between E2 and E3. In two-electrode system simulations (b), E2 and E3 were the current feeding and counter electrode, respectively. In four-electrode system simulations (a), E1 and E4 were the current feeding and counter electrode, respectively, and E2 and E3 were the recording electrodes. The coordinate system used in the paper is shown in a