Microfabricated PEDOT trilayer actuators: synthesis, characterization, and modeling

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.