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Proceedings Paper

Polypyrrole actuators: modeling and performance
Author(s): John David Madden; Peter Geoffrey Madden; Ian Warwick Hunter
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Paper Abstract

Conducting polymer actuators generate forces that exceed those of mammalian skeletal muscle by up to two orders of magnitude for a given cross-sectional area, require only a few volts to operate, and are low in cost. However application of conducting polymer actuators is hampered by the lack of a full description of the relationship between load, displacement, voltage and current. In an effort to provide such a model, system identification techniques are employed. Stress-strain tests are performed at constant applied potential to determine polypyrrole stiffness. The admittance transfer function of polypyrrole and the associated electrolyte is measured over the potential range in which polypyrrole is highly conductive. The admittance is well described by treating the polymer as a volumetric capacitance of 8*107 F*m3 whose charging rate is limited by the electrolyte resistance and by diffusion within polypyrrole. The relationship between strain and charge is investigated, showing that strain is directly proportional to charge via the strain to charge density ratio, (alpha) = 1*10+-10 m3*C-1, at loads of up to 4 MPa. Beyond 4 MPa the strain to charge ratio is time dependent. The admittance models, stress/strain relation and strain to charge relationship are combined to form a full description of polypyrrole electromechanical response. This description predicts that large increases in strain rate and power are obtained through miniaturization, yielding bandwidths in excess of 10 kHz. The model also enables motor designers to optimize polypyrrole actuator geometries for their applications.

Paper Details

Date Published: 16 July 2001
PDF: 12 pages
Proc. SPIE 4329, Smart Structures and Materials 2001: Electroactive Polymer Actuators and Devices, (16 July 2001); doi: 10.1117/12.432688
Show Author Affiliations
John David Madden, Massachusetts Institute of Technology (United States)
Peter Geoffrey Madden, Massachusetts Institute of Technology (United States)
Ian Warwick Hunter, Massachusetts Institute of Technology (United States)

Published in SPIE Proceedings Vol. 4329:
Smart Structures and Materials 2001: Electroactive Polymer Actuators and Devices
Yoseph Bar-Cohen, Editor(s)

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