Redox level-dependent impedance model for conjugated polymer actuators

The reduction-oxidation (redox) level of a conjugated polymer has significant impact on its electro-chemo-mechanical properties, such as conductivity, impedance, and Young's modulus. A redox level-dependent impedance model is developed in this paper by including the dynamics of ion diffusion, ion migration, and redox reactions. The model, in the form of a transfer function, is derived through perturbation analysis around a given redox level. Experimental measurements conducted under different redox conditions correlate well with the model prediction and thus validate the proposed model. This work, for the first time, incorporates the effect of redox level into the dynamics of conjugated polymers, and facilitates the future use of nonlinear control methods for the effective control of these materials.