Conducting polymers are active materials that exhibit an interesting bidirectional electromechanical coupling, where an input voltage results in the displacement of the film and a voltage is produced when a displacement is applied to the film. Mechanical deformation of the transducer by external mechanical loads causes movement of ions, and the generation of voltages. In this work, a dual sensing and actuation model for conducting polymer is described. The model comprises an RC lumped circuit, representing the electrochemical model, a mechanical model described by a dynamic Euler – Bernoulli beam theory, and an empirical strain-to-charge ratio. All three submodels are presented in a self-consistent Bond Graph formalism. The predictions of this model are then demonstrated by comparing with the experimental sensing and actuation results of a 17 µm thin poly(3,4-ethylenedioxythiophene) – based trilayer transducer, showing that the complete electromechanical model elucidates an effective approach to describe both sensing and actuation.
Conducting polymer actuators have long been of interest as an alternative to piezoelectric and electrostatic actuators due to their large strains and low operating voltages. Recently, poly (3,4- ethylenedioxythiophene) (PEDOT) – based ionic actuators have been shown to overcome many of the initial obstacles to widespread application in micro-fabricated devices by demonstrating stable operation in air and at high frequencies, along with microfabrication compatible processing using a layer by layer method that does not require any handling. However, there is still a need for characterization, prediction, and control of the actuator behavior. This paper describes the fabrication and characterization of thin trilayers composed of a 7 μm thick solid polymer electrolyte (SPE) sandwiched between two 2.1 μm thick PEDOT-containing layers. Beam properties including capacitance, elastic moduli of the layers, and the extent of charge driven strain, are applied to predict curvature, frequency response and force generation. The actuator is represented by an electrical circuit, a mechanical system described via dynamic beam theory, and a strain-to-charge ratio for the electro-mechanical coupling matrix, which together predict the actuator curvature and the resonant response. The success of this physical model promises to enable design and control of micro-fabricated devices.