A finite element model for bending behaviour of conducting polymer electromechanical actuators

Emerging conducting polymer electromechanical actuators (CPEA) have many potential applications ranging from biomedical to micro/nano manipulation systems. In order to make use of their potential, it is needed to establish a valid mathematical model to provide enhanced degrees of understanding, predictability, control and efficiency in performance. Although it is known that the mechanism behind their operation is quite straightforward; establishing a mathematical model to predict their behaviours and quantify their performance is hampered by many mechanical, electrical and chemical parameters. With this in mind, the aim of this study is to establish and experimentally validate a lumped-parameter model of bending-type polypyrrole (PPy) actuators for use in improving their displacement and force outputs. With reference to their operation principle, we draw an analogy between the thermal strain and the real strain in the PPy actuators due to the volume change to set up the mathematical model, which is a coupled structural/thermal model. The finite element method (FEM) is used to solve the model. The effect of propagation of the ion migration into the PPy layers is mimicked with a temperature distribution model. Theoretical and experimental results demonstrate that the model is practical and effective enough in predicting the bending angle and bending moment outputs of the PPy actuators quite well for a range of input voltages, and the PPy layer thicknesses.