title: Training effect and fatigue in polypyrrole-based artificial muscles.
abstract: Artificial muscles based on an electrochemomechanical strain (ECMS) in conducting polymers, namely polypyrrole (PPy) film, have been studied from viewpoints of training, fatigue and aging by repeat cycles under tensile loads. ECMS was approximately 2% in a saline solution, resulting from both insertion and exclusion of Na(+) with solvated water molecules as well in the film. Transient responses of ECMS and current induced by voltage stimuli were measured under tensile stresses up to 5 MPa to see the training effect, fatigue and aging of the film. At higher stresses the film showed larger creeping, which resulted from realignment or conformation change, slipping and breaking of polymer chains. After the experience of large stresses, the training effect in ECMS was appreciably observed as an increase of the strain. Without stress the conductivity of the film was stable (no fatigue) upon an electrochemical cycle; however, under high tensile stresses the conductivity decreased remarkably (fatigue and aging). It is to be noted that straightened polymer chains can be easily oxidized and degraded due to lower pi-electron energy. The conversion efficiency from electrical to mechanical energy in this system was found to be less than 0.03%.
authors.affiliation: Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kaneto
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Suematsu
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yamato
mesh_terms: D000818:Animals; D040761:Biomimetic Materials; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D017711:Nonlinear Dynamics; D011108:Polymers / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D011108:Polymers; D011758:Pyrroles; C067635:polypyrrole