Figure 3.

Equivalent circuit of the interface between skin and electrodes in the case of (a) wet electrodes and (b) textile electrodes. The figure was adapted from [27]. E_hc represents the electrode; C_d and R_d represent the impedance due to the sensor-electrolyte interface; C_t (only present in textile electrodes) and R_s represent an impedance due to the electrolyte layer; C_e and R_e represent the middle-layer impedance; C_p and R_p represent the sweat glands; R_a represents the inner-layer impedance, acting as a pure resistance in both cases.