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.

[1]  S. Nemat-Nasser.  Micromechanics of actuation of ionic polymer-metal composites , 2002 .

[2]  Elisabeth Smela,et al.  Electrochemically driven polypyrrole bilayers for moving and positioning bulk micromachined silicon plates , 1999 .

[3]  D. Rossi,et al.  Characterization and modelling of a conducting polymer muscle-like linear actuator , 1997 .

[4]  Der Ho Wu,et al.  Coupled-field analysis of piezoelectric beam actuator using FEM , 2004 .

[5]  Ingemar Lundström,et al.  Polypyrrole micro actuators , 1999 .

[6]  G. Wallace,et al.  Development of polypyrrole-based electromechanical actuators , 2000 .

[7]  E. Smela,et al.  Fabrication of folding microstructures actuated by polypyrrole/gold bilayer , 2003, TRANSDUCERS '03. 12th International Conference on Solid-State Sensors, Actuators and Microsystems. Digest of Technical Papers (Cat. No.03TH8664).

[8]  H. Elias.  An introduction to plastics , 1993 .

[9]  B. S. Berry,et al.  Bending-cantilever method for the study of moisture swelling in polymers , 1984 .

[10]  G. Wallace,et al.  Strain Response from Polypyrrole Actuators under Load , 2002 .

[11]  R. Baughman.  Conducting polymer artificial muscles , 1996 .

[12]  Jianbin Luo,et al.  Design and evaluation of PZT thin-film micro-actuator for hard disk drives , 2004 .

[13]  I. Hunter,et al.  Fast contracting polypyrrole actuators , 2000 .

[14]  E. Smela.  Conjugated Polymer Actuators for Biomedical Applications , 2003 .

[15]  W.J. Li,et al.  Polymer MEMS actuators for underwater micromanipulation , 2004, IEEE/ASME Transactions on Mechatronics.

[16]  Staffan Greek,et al.  Deflection of surface-micromachined devices due to internal, homogeneous or gradient stresses , 1999 .

[17]  D. De Rossi,et al.  Performance and work capacity of a polypyrrole conducting polymer linear actuator , 1997 .

[18]  Yoseph Bar-Cohen,et al.  Electroactive polymers (EAP) charaterization methods , 2000, Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[19]  Gursel Alici,et al.  A methodology towards geometry optimization of high performance polypyrrole (PPy) actuators , 2006 .

[20]  I. Lundström,et al.  Microrobots for micrometer-size objects in aqueous media: potential tools for single-cell manipulation. , 2000, Science.

[21]  Dezhi Zhou,et al.  Conducting polymers electromechanical actuators and strain sensors , 2003 .

[22]  Binbin Xi,et al.  Enhanced control and stability of polypyrrole electromechanical actuators , 2004 .

[23]  H. Lobo,et al.  Handbook of Plastics Analysis , 2003 .

[24]  Edward L. Wilson,et al.  Numerical methods in finite element analysis , 1976 .

[25]  Q. Pei,et al.  Electrochemical applications of the bending beam method. 1. Mass transport and volume changes in polypyrrole during redox , 1992 .

[26]  Sia Nemat-Nasser,et al.  Electromechanical response of ionic polymer-metal composites , 2000 .