title: Redox-induced surface stress of polypyrrole-based actuators.
abstract: We measure the surface stress induced by electrochemical transformations of a thin conducting polymer film. One side of a micromechanical cantilever-based sensor is covered with an electropolymerized dodecyl benzenesulfonate-doped polypyrrole (PPyDBS) film. The microcantilever serves as both the working electrode (in a conventional three-electrode cell configuration) and as the mechanical transducer for simultaneous, in situ, and real-time measurements of the current and interfacial stress changes. A compressive change in surface stress of about -2 N/m is observed when the conducting polymer is electrochemically switched between its oxidized (PPy+) and neutral (PPy0) state by cyclic voltammetry. The surface stress sensor's response during the anomalous first reductive scan is examined. The effect of long-term cycling on the mechanical transformation ability of PPy(DBS) films in both surfactant and halide-based electrolytes is also discussed. We have identified two main competing origins of surface stress acting on the PPy(DBS)/ gold-coated microcantilever: one purely mechanical due to the volume change of the conducting polymer, and a second charge-induced, owing to the interaction of anions of the supporting electrolyte with the gold surface.
authors.affiliation: Physics Department, McGill University, Montréal, Québec, Canada. vtbar@physics.mcgill.ca
authors.forename: Vincent
authors.initials: V
authors.lastname: Tabard-Cossa
authors.forename: Michel
authors.initials: M
authors.lastname: Godin
authors.forename: Peter
authors.initials: P
authors.lastname: Grütter
authors.forename: Ian
authors.initials: I
authors.lastname: Burgess
authors.forename: R B
authors.initials: RB
authors.lastname: Lennox
mesh_terms: D000465:Algorithms; D001557:Benzenesulfonates / Q000737:chemistry; D001966:Bromine / Q000737:chemistry; D004563:Electrochemistry; D006046:Gold; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D011758:Pyrroles / Q000737:chemistry*; D012965:Sodium Chloride; D013314:Stress, Mechanical; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D001557:Benzenesulfonates; D011758:Pyrroles; D013501:Surface-Active Agents; D012965:Sodium Chloride; C001114:dodecylbenzenesulfonic acid; D006046:Gold; D001966:Bromine