Actuation cation-driven

Trilayer PPy actuators have also been constructed in which PPy is electrodeposited on either side of a gold electrode using the large DBS ion on one side (cation-driven PPy) and a smaller benzenesulfonate on the other (anion-driven PPy), which bent quickly in a cooperative manner as the trilayer was oxidized or reduced in 1 M LiC104 [26]. A problem with any design in which the conducting-polymer remains attached to an inert metal... 

The out-of-plane actuator of PPy doped with polystyrene sulfonate (cation-driven) was also studied in a systematic manner using AFM [50]. Larger strains of up to 12.3% were obtained for thinner films (97 nm), which decreased as the PPy thickness was increased (to 5.5% strain for a 3.17 pm thick film). The strain with thicker films was also more dependent upon voltammetric scan rate, ascribed to a large increase in diffusion... 

In addition to nanostructural properties of the conducting polymer, considerable influence on actuation behavior has been demonstrated due to the choice of electrolyte. This has included properties of the solvent employed, and crucially the size of doping ions and their interaction with the conducting polymer. As mentioned above, PPy films doped with moderately small anions (e.g. CP) lead to actuation driven by anion movement. By contrast, it is generally found that the inclusion of a large dopant anion (e.g. DBS) within PPy leads to cation-driven actuation, typically when a smaller cation is employed (e.g. Na ). However, it is not always a simple matter of predicting which movement, anion or cation, will predominate for a particular electrolyte system, and for a particular type of... 

R. Kiefer, G.A. Bowmaker, R.P. Cooney, P.A. Kilmartin, and J. Travas-Sejdic, Cation driven actuation for free standing PEDOT films prepared from propylene carbonate electrolytes containing TBACF3SO3, Electrochim. Acta, 53 (5), 2593-2599 (2008). 

Fig. 9 (a) Schematic stmcture of a tri-layer conducting polymer actuator and (b) schematic representation of the bending principle. This actuator is anion driven the anions in the salt move into the positively charged electrode to cause a volmne expansion. If it is cation driven, the cations in the salt move into the negatively charged electrode to cause volume expansion hence, the bending direction will be from the negative electrode to the positive electrode - the opposite of what is shown (Alici 2009)... 

IPMC actuators exhibit a typical strain of 0.5 %, strain rate of 3 %/s and a typical stress of 3 MPa. They are actuated at potentials of <10 V [42]. The performance of these actuators has been improved by using various combinations of cations [23-25] and different types of electrodes, such as platinum-copper [26]. In this chapter a brief overview of different designs and test procedures using this type of actuators is presented, as similar approaches could also be employed in conjugated polymer driven devices. IPMC based steerable catheters are further described in another chapter of this book. 

This suggests that the initial curvature is driven by the pressure gradient caused in the ion gel by the electroosmosis flow. Hence, the initial curvature is a function of the ionic charge, Q, and the water transference coefficient, Xla, which describes the number of water molecules transferred per counter cation transferred. The experimentally determined initial curvature of an IPMC actuator (Naflon 117/Au) having various ionic forms could be reproduced with fidelity using the theoretical curves described by Eqs. 17, 18, and 20 (Yamaue et al. 2005). 

Macroanions are present in blends of conducting polymers. The macroanion remains trapped in the material during oxidation/reduction forcing the exchange of cations (C ) for charge balance and solvent for osmotic balance. The actuation-driven reaction can be summarized as... 

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