In this paper, a model to describe the electrochemomechanical behavior of conducting polymer (CP) based tri-layer transducer is proposed. This model will be used for simulation, control and estimation purposes. Energetic Macroscopic Representation (EMR) has been investigated in order to provide a displacement estimator and an inversion-based control for position feedback of the CP based actuator (CPBA). This work is illustrated with experimental and simulation results.
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.
Modelling trilayer conducting polymer is still challenging as it exhibits interrelated coupled multiscale and non-linear characteristics. Therefore, this work proposes to review the underlying electro-chemo-mechanical principles in ultrathin PEDOT trilayer ionic conducting polymers based upon internal ion charge transport, conduction phenomena, redox process and elastic deformation. Microscale governing equations are first analyzed and the choice of appropriate assumptions depending of the used material is discussed. Since exact analytical solutions can be so far given only for some limited conditions, numerical solutions are developed to solve the problem. Then simulations in both sensing and actuating are successfully compared with experiments.
In this paper, the electrical response of ionic electro-active polymer (IEAP) based tri-layer micro-actuator al- lowing to consider some phenomena which occur in the micro-actuator behavior is presented. A detailed study on the measured currents during charging and discharging process is analyzed. Electrical charges, time con- stants, capacitance and resistance of the simplified equivalent electrical circuit are investigated. The results have shown that, the micro-actuator exhibits a linear behavior for applied voltage lower than 1 V. Beyond that, non- linearities appear and are related to the discharging process, especially the corresponding electrical resistance which increases in a non-linear way. At this stage, accumulated electrical charges which depend on the previously applied voltage are not totally restored during the discharging process. The results of this study are illustrated with experimental and theoretical results.
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