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A Dynamic Electromechanical Model for Electrochemically Driven Conducting Polymer Actuators

Publication Type:

Journal Article

Source:

IEEE-ASME TRANSACTIONS ON MECHATRONICS, Volume 16, Number 1, p.42-49 (2011)

Keywords:

Active catheter; actuator; analytical model; constant phase element; electrochemical double layer capacitor; polypyrrole; transmission line

Abstract:

In this paper, an analytical model is presented to predict the actuation
response of electrochemically driven structures. A 2-D impedance model
is first presented that uses a conducting polymer RC transmission line
equivalent circuit to predict the charge transfer during actuation. The
predicted electrochemical charging is then coupled to a mechanical model
to find the actuation response of a bending structure. The advantage of
this model compared to existing models is that it represents the 2-D
charging of the polymer, namely through the thickness of the polymer
structure and along its length. The model considers both ion
``diffusion'' through the thickness and electronic resistance along
the length. The output of the impedance model is charge density in the
polymer as a function of position and time, which is then used to
estimate free strain via the strain to charge ratio. Given the modulus
of the polymer and of passively deformed structures, time-dependent
deformation is then determined. The complete electromechanical model is
a function of ionic and electronic conductivities, dimensions,
volumetric capacitance, elastic modulus, and strain to charge ratio, all
of which are measured independently. The full electromechanical model is
shown to provide a good description of the response of bending polymer
structures when comparing with experimental results. The model can be
effectively used as a design tool for electrochemically driven devices.