Physical Interpretation of the Warburg Impedance

Effect of thermal treatment and applied potential on the electrochemical behaviour of CoCrMo biomedical alloy

“…7b and the electrical parameters are shown in Table 4. The elements of the equivalent circuit proposed are R s (solution resistance), CPE out (constant phase element of the double layer), R out (charge transfer resistance of the outer layer) and W-R (Warburg element) related to mass transport limitation by diffusion [31,36,37]. The high frequencies loop can be attributed to the charge transfer which takes place at the interface.…”

On the cause and control of residual voltage generated by electrical stimulation of neural tissue

“…However there exists a net residual voltage at the end of the anodic pulse, even if the biphasic stimulus is completely charge balanced [7]. The residual voltage is due to the Faradaic impedance [6] as well as mismatch errors in the transistors used to make the stimulator. The presence of a residual voltage may lead to irreversible chemical reactions at the electrode-tissue interface and cause tissue damage [8].…”

“…2(b). An insight into the physical interpretation of the Warburg impedance can be found in [6]. However, for the purposes of this design, the parallel Faradaic impedance has been modeled here as a linear resistor.…”

“…The output voltage at the end of the anodic pulse was sampled and sent to a proportional feedback controller, implemented in software by the microcontroller. The calculated width of the instantaneous anodic pulse is, (6) where k is the proportional feedback parameter. The set point voltage (V SP ) was 0 V and the value of k was selected to be high enough to provide feedback and not induce oscillations in the system.…”

“…Oxidation-reduction reactions at the electrode/electrolyte interface give rise to current flow that is modeled by a charge-transfer resistance R ct . The mass transport limitations of ions in the electrolyte is modeled by the Warburg impedance [6]. Together, the charge-transfer resistance and Warburg impedance can be lumped as a Faradaic impedance [3].…”