Actuation of PPy

In a series of experiments, a variety of electrolytes were evaluated. Suitable electrolytes for the actuation of PPy were found to be watery solutions of NaDBS, NaCl, Na2S04, LiCl in the range of concentration from 0.01 to 0.5 M (physiological NaCl solution cotrcsprmds to a concentration of 0.0154 M) and artificial saliva. Solutions of Naltrexone are not suited for 

In each case, the sample was actuated in a three-electrode setup by linearly ramping the potential WE(PPy)-RE(Ag/AgCl) between 0 and — 1 V within 200 s. The potentials that are applied between PPy and CE differ significantly. In the case of a CE fabricated in silver, a full redox cycle could be obtained with WE-CE potentials between —0.5 and —1.2 V (compare the potentials for the oxidation and reduction peaks in current). In this case, the potentials can be kept below the threshold voltage for the occurrence of hydrolysis. Furthermore, the applied voltages do not need to be switched from positive to negative values, which simplifies required control electronics. 

---

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... 

Maw S, Smela E, Yoshida K, Stein RB (2005) Effects of monomer and electrolyte concentrations on actuation of PPy(DBS) bilayers. Synth Met 155 18-26 Melling D, Wilson SA, Beiggren M, Jager EWH (2011) Altering the structure of polypyrrole and the influence on electrodynamic performance. In Proceedings of SPIE - The International Society for Optical Engineering, vol 7976... 

The actuation force or movement generated during redox cycling is directly related to the concomitant changes in mechanical properties. Using a simple linear elastic model of the small-strain mechanical properties of PPy, it has been shown that the actuation strain (eo) at a constant applied stress (a) is accurately predicted from Equation 3.3... 

A composite actuator was constructed using a copolymer of PPy and poly(methoxyaniline) formed in p-phenol sulfonic acid (PPS). Higher actuation deformations were seen at low pH. Pure PPy(PPS) initially showed mixed cation and anion actuation when tested in 1 M NaCl, but the cathodic expansion was removed by the inclusion of 30% poly(methoxyani-line) and the extent of electrochemical creep was also diminished [144]. The inclusion of poly(2-methoxyaniline-5-sulfonate) (PMAS) into PPy(DBS) films improved the cathodic expansion of the films. The presence of the PMAS also led to some anodic film expansion in some electrolytes (e.g. KCl), but exclusively enhanced cation expansion in other electrolytes (TBAPF4) [145]. 

M. Christophersen, B. Shapiro, and E. Smela, Characterization and modeling of PPy bilayer microactuators. Part 1. Curvature, Sens. Actuators, B, B115 (2), 596-609(2006). 

S.Y. Chu, H. Peng, P.A. Kilmartin, G.A. Bowmaker, R.P. Cooney, and J. Travas-Sejdic, Effect of deposition current density on the hnear actuation behaviour of PPy(CF3S03) films, Curr. Appl. Phys., 8 (3 ), 324-327 (2008). 

FIGURE 8.85 Video images of the bending actuation of the doped film with the wrinkled PPy electrode and the conventional gold electrode. The applied voltage was 1000 V (the electric field was 5 MV/m). (From Watanabe, M., Shirai, H., and Hirai, T., /. Appl. Phys., 92, 4631, 2002. With permsission.)... 

Christophersen, M., and E. Smela. (in press). Characterization and modeling of PPy bUayer microactuators. Part 4 Effect of temperature. Sensor Actuator B. 

The trilayer PPy actuator is illustrated in Fig. 5.1. On both sides of the actuator are PPy layers. In the middle is an amorphous, porous pol3cvinyli-dene fluoride (PVDF) layer that serves both as a backing material and a reservoir for the electrolyte, which allows the actuator to work in air for a limited period of time (up to several hours). During the electrochemical deposition of the PPy layers, anions A in the electrolyte are introduced into the polymer matrix, which is a process called doping. When a voltage is ap-... 

We have fabricated the torsional actuator by depositing PPy on a tube substrate with helically wound platinum fibers. While the fabrication process follows closely the work of Ding et al. [Ding et al. (2003)], they adopted the approach for a different purpose and did not examine torsional actuation of such devices. We have conducted experiments on actuators with different dimensions and fiber winding angles, which have not only confirmed torsion and other deformation modes of these actuators but also validated the nonlinear mechanical model. 

---