Masaki Fuchiwaki

Cyclic step-voltammetric analysis of cation-driven and anion-driven actuation in polypyrrole films

Cation-driven and anion-driven electrochemomechanical deformations (ECMD) in electrodeposited polypyrrole (PPy) films have been investigated by means of cyclic voltammetry and cyclic step-voltammetry (CSV). The film deposited from hydrochloric acid (PPyCl) expanded upon anodic reaction (anodic expansion) while that deposited from dodecyl-benzene sulfonic acid (PPyDBS) exhibited cathodic expansion. In the case of the film deposited from p-phenol sulfonic acid (PPyPPS), it was found to show the anodic expansion at 600 mV (vs Ag wire as a reference electrode) along with the cathodic contraction at -800 mV in CSV. The film obtained from the same lot, however, showed cathodic contraction and anodic expansion only by changing the oxidative potential from 600 mV to -100 mV. This phase inversion indicates that not only the polymerization electrolyte but also the redox potential determines the (de)insertion of ions in the PPyPPS film. Contractive electrochemical creeping was only observed in PPyPPS film in chloride salt electrolytes, indicating that the cation insertion induces the deinsertion of initial-dopant anion from the film.

Structural Electrochemistry from Freestanding Polypyrrole Films: Full Hydrogen Inhibition from Aqueous Solutions

Free-standing polypyrrole fi lms, being the metal‐polymer contact located several millimeters outside the electrolyte, give stationary closed coulovoltammetric (charge/potential) loop responses to consecutive potential sweeps from ‐2.50 V to 0.65 V in aqueous solutions. The continuous and closed charge evolution corroborates the presence of reversible fi lm reactions (electroactivity), together high electronic and ionic conductivities in the full potential range. The closed charge loop demonstrates that the irreversible hydrogen evolution is fully inhibited from aqueous solutions of different salts up to ‐2.5 V vs Ag/AgCl. The morphology of the closed charge loops shows abrupt slope changes corresponding to the four basic components of the structural electrochemistry for a 3D electroactive gel: reduction-shrinking, reduction-compaction, oxidation-relaxation, and oxidation-swelling. Freestanding fi lms of conducting polymers behave as 3D gel electrodes (reactors) at the chain level, where reversible electrochemical reactions drive structural conformational and macroscopic (volume variation) changes. Very slow hydrogen evolution is revealed by coulovoltammetric responses at more cathodic potentials than ‐1.1 V from strong acid solutions, or in neutral salts self-supported blend fi lms of polypyrrole with large organic acids. Conducting polymers overcome graphite, mercury, lead, diamond, or carbon electrodes as hydrogen inhibitors, and can compete with them for some electro-analytical and electrochemical applications in aqueous solutions.

Polypyrrole–para-phenolsulfonic acid/tape artificial muscle as a tool to clarify biomimetic driven reactions and ionic exchanges

Thick films of the polypyrrole-para-phenolsulfonic acid (PPy-HpPS) blend were electrogenerated on stainless steel plates. The self-supported films, once peeled off from the metal, were electrochemically characterized in aqueous solutions of NaCl and NaPF6. The Na, Cl, P, S and F content of films, after attaining a different oxidation state, were determined by EDX. The bending movements of the bilayer (PPy-HpPS)/tape artificial muscle were video recorded during potential sweeps in both solutions allowing the translation of the prevalent ionic exchanges driven by the biomimetic reactions into macroscopic movements. Ionic exchanges between the film and the solution, biomimetic structural processes in the film, driving prevalent electrochemical reactions and film compositions related to each of the different structural potential domains defined by coulovoltammetric results were clarified. In NaPF6 solutions a prevalent exchange of anions exists: the film swells by oxidation and shrinks by reduction. In NaCl solutions prevailing exchange of cations or anions occurs in different potential ranges. Reactions related to the HpPS content play important roles at the more cathodic and more anodic overpotentials. The described methodology could be translated to biological reactions including reactive biopolymers.

Effect of film morphology on the actuation behaviour in polypyrrole films

Polypyrrole (PPy) has been electrochemically synthesized on different substrates using aqueous solution of β-Naphthalene sulphonic acid (β-NSA). Scanning electron microscopy revealed different film morphology of PPy electrodeposited on different substrates. A direct measurement of electrochemomechanical deformation (ECMD) characteristics is discussed in films of PPy doped with β-NSA having different film morphologies. An attempt is being made to delineate the role of morphology on the ECMD in the freestanding films of PPy.

Comparative Study of Electrochemomechanical Deformations of Poly(3-alkylthiophene)s, Polyanilines and Polypyrrole Films

Expansion and contraction in regioregular and regiorandom poly(3-alkylthiophene), PAT films (alkyl=hexyl and dodecyl) upon electrochemical oxidation and reduction in organic electrolyte solvents are studied. It is found that the deformed films consist of two components, which respond to electrochemical cycle and creeping. The PAT films with short alkyl chain length show relatively large deformation by the electrochemical cycle, because of the higher density of electroactive π-electron components. The expansion/contraction ratio of PAT films is discussed taking the morphology into consideration and comparing it with the results for the other conducting polymers of polyaniline and polypyrrole films.

Soft Actuators Based on Poly(3-alkyl thiophene) Films Upon Electrochemical Oxidation and Reduction

Expansion and contraction in poly(3-alkylthiophene), with alkyl = hexyl and dodecyl, films upon electrochemical oxidation and reduction are measured. The expansion of films is found to consist of two components, which are responding to electrochemical cycle and creeping. The expansion ratio and the creeping are discussed taking the morphology of films into consideration, and compared with the case of polyaniline and polypyrrole.

Proposal of Novel Actuators Using Conducting Polymer Laminates

Three kinds of novel actuators based on conducting polymer laminates, polypyrrol, have been proposed and these actuation have been observed in 1.0 M sodium chloride / aqueous solution. It was confirmed that the stick type actuator performed bending actuation with large amplitude, high durability and response. Moreover, in the ring type and lip type actuators, their shapes changed largely. Especially, the lip type actuator closed completely in the reduction state, and it spread largely in the oxidation state.

Characteristics of Butterfly Wing Motions and Their Application to Micro Flight Robot

Many researchers have attempted to develop MAV and micro-flight robot with various actuators and devices so far however their studies have not led to practical applications yet. One of the reasons is that flying mechanism of birds and insects has not been clarified sufficiently. In this study, we evaluate dynamic behaviors of a wing observed from the butterflys viewpoint in its flight. The authors conduct a flight observation experiment of Cynthia cardui performing a free flight and fixed flight and an image analysis and calculate flapping angles, lead-lag angle and feathering angles of the butterfly performing flapping flight to clarify the relation between them. Furthermore, we aim at developing the micro flight robot like the butterfly using these results. The micro flapping robot flied stably for 12 minutes, which was the batterys duration.

Performance of a Micro Pump Driven by Conducting Polymer Soft Actuator Based on Polypyrrole

Micro pumps are essential components of micro-fluidic systems and bio-sensing systems. In particular, the micro pump used for -TAS transports fluids at a micro flow rate with high precision. This micro pump is also used to transport high-viscosity fluids because there are various types of drugs to be transported. We developed a micro pump driven by a conducting polymer soft actuator that opens and closes. Although the developed micro pump contains no valve, the micro pump can transport fluids in one direction without backflow. A newly developed micro pump driven by a conducting polymer soft actuator can transport fluids in one direction without backflow by the opening and closing of two soft actuators.

Wake Structure of Heaving Elastic Airfoils and Their Dynamic Thrust

An unsteady flow in a low Reynolds number region attracts attention in recent years. The authors measured vortex flow in the wake of the rigid flat plate, rigid NACA0010, elastic flat plate and elastic NACA0010 with heaving motions and evaluated accelerating flows induced by the vortex flow patterns and vortex flows in the wake of the airfoils. Furthermore, we measured dynamic thrusts acting on these airfoils with heaving motions and clarified their relations with vortex flows. The clear thrust producing vortex street is formed in the wake of the elastic airfoils even at a comparatively low Strouhal number. The clear accelerating flow is formed in the wake of the elastic airfoils. The dynamic thrusts that act on the rigid NACA0010, elastic flat plate and elastic NACA0010 are strongly dependent on the Strouhal number based on the trailing edge amplitude regardless of heaving amplitudes, heaving frequencies, airfoil shapes and elastic deformations.Copyright