title: Asymmetric Bilayer Muscles: Cooperative Actuation, Dynamic Hysteresis, and Creeping in NaPF6 Aqueous Solutions.
abstract: Three bilayer muscles [polypyrrole-paraphenolsulfonic acid/polypyrrole-dodecylbenzensulfonic acid (PPy-HpPS/PPy-DBS) asymmetric bilayer, PPy-HpPS/tape, and PPy-DBS/tape] were characterized during potential cycling in NaPF6 aqueous solutions. In parallel, the angular displacement of the muscle was video-recorded. The dynamo-voltammetric (angle-potential) and coulo-dynamic (charge-potential) results give the reaction-driven ionic exchanges in each PPy film. Electrochemical reactions drive the exchange of anions from the PPy-HpPS layer and cations from the PPy-DBS layer. This means that both layers from the asymmetric bilayer follow complementary volume changes (swelling/shrinking or shrinking/swelling), owing to complementary ionic exchanges (entrance/expulsion) driven by the bilayer oxidation or reduction. The result is a cooperative actuation; the bending amplitude described by the asymmetric bilayer muscle is one order of magnitude larger than those attained from each of the conducting polymer/tape muscles. The cooperative actuation almost eliminates creeping effects. A large dynamical hysteresis persists, which can be attributed to an irreversible reaction of the organic acid components at high overpotentials.
authors.affiliation: Department of Mechanical Information Science and Technology Kyushu Institute of Technology 680-4 Kawazu Iizuka Fukuoka 820-8502 Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Fuchiwaki
authors.affiliation: Center for Electrochemistry and Intelligent Materials Universidad Politécnica de Cartagena Aulario II, C/Carlos III, s/n 30203 Cartagena Spain.
authors.forename: Jose G
authors.identifier: 0000-0002-6490-8603
authors.initials: JG
authors.lastname: Martinez
authors.affiliation: Center for Electrochemistry and Intelligent Materials Universidad Politécnica de Cartagena Aulario II, C/Carlos III, s/n 30203 Cartagena Spain.
authors.forename: Toribio
authors.identifier: 0000-0002-8517-1428
authors.initials: T
authors.lastname: Fernandez Otero
keywords: asymmetric bilayer muscles; conducting polymers; cooperative actuation; creeping; hysteresis