Memory effect and dynamics in PEDOT:PSS-based actuators under DC voltage

摘要

Conducting polymers have interested many research groups as they exhibit a large strain in response to electrical stimulation, which is promising for materials used in MEMS. To date, these micro-actuators have very often been characterized by applying an AC voltage to extract the produced strains and forces. However, many applications require subjecting the actuators to an electrical voltage threshold for about 10 seconds or until several minutes. A micro-camera tracking the displacements of an object, the actuation of a cochlear implant during surgery, or the closing of micro-tweezers for manipulation objects are potential applications for which actuation is achieved by applying a DC voltage. In this way, the kinetics to reach the maximum strain are identified and compared. The application of a DC voltage to the conducting polymer-based micro-actuator for an extended period of time results in the emergence of a "memory effect". In particular, the actuator does not return to its initial position promptly after a short-circuit. In addition, the electromechanical measurements conducted show that the deformation obtained depends on the DC voltage used for the previous actuation. The memory effect is directly related to the intrinsic operation of micro-actuator trilayers where the separator (NBR/PEO) is filled with an ionic liquid electrolyte that is involved during oxidation and reduction of the conductive polymer electrodes (PEDOT:PSS/PEO). An explanation of the physico-chemical phenomena involved will be proposed. These results are needful for the modeling and future control of these conjugated polymer micro-actuators integrated into microsystems devices for real-life applications.