Role of charge carriers in long-term kinetics of polyurethane electroactuation

Previous work has shown that dielectrophoretic body forces resulting from permittivity and conductivity heterogeneities only partially contribute to the overall electromechanical deformation of segmented polyurethanes (PUs). In this work, we studied the experimental kinetics and electric current of PU thin films over a long time period (1–10⁵ s) for different applied electric fields. Then, we thoroughly analyzed the drift behavior of electric carriers and its macroscopic effect using simple modeling and numerical simulation. The main assumption is that the macroscopic deformation results from the accumulation of electric charges near the electrodes, leading to local stretching. Assuming that the mobilities of negative and positive carriers are different, their migration towards the electrodes will have different kinetics. A preliminary simulation attempt using a single set of parameters, supports these assumptions, and leads to a correct bending amplitude and current evolution according to the applied electric field. Furthermore, the resulting compression is consistent with the observed electrostriction.