Characterization of a non linear fractional model of electrode-tissue impedance for neuronal stimulation

The design of neuro-stimulators must include a realistic model of electrode-tissue interface. Complex electrochemical phenomena associated to high levels of stimulation current give fractional and non linear behavior to this interface that simple linearized models fail to fit. This paper describes both a measurement protocol based on biphasic current-controlled solicitations and a modeling procedure relying on an original approach of multi-model, taking into account the non-linear and fractional effects. This model fits correctly the measurement results with current levels varying from 50μA to 1mA. Furthermore the whole characterization protocol can be safely transposed to in vivo measurements.