Electrically active polymer materials actuation

There is another type of electrically active polymer that is known as the electroconductive polymer, in which polymer chains contain long conjugated double bonds, and this chemical structure adds electroconductive properties to the polymers. In these cases, the electrically induced deformation is considered to have originated from the electrochemical reactions such as the oxidation and reduction of the polymer chain. For the deformation, some additives such as dopants have been known to be necessary for effective actuation. Therefore, the electrical actuation of these materials has been... 

Today the number of electroactive polymers has grown substantially. There currently exists a wide variety of such materials, ranging from rigid carbon-nanotubes to soft dielectric elastomers. A number of reviews and overviews have been prepared on these and other materials for use as artificial muscles and other applications [1, 2, 7, 10, 11, 13-28]. The next section will provide a survey of the most common electrically activated EAP technologies and provide some pertinent performance values. The remainder of the paper will focus specifically on dielectric elastomers. Several actuation properties for these materials are summarized in Table 1.1 along with other actuation technologies including mammalian muscle. It is important to note that data was recorded for different materials under different conditions so the information provided in the table should only be used as a qualitative comparison tool. 

The overall electroactivity of carbon-based actuators, including CNTs, CDCs, or activated carbons, predicates on two main actuation mechanisms. The first principle is based on the electronic (metallic) conductivity of carbon material. Actuators of such type need high electrical potential (field) for actuation. Actuation occurs due to carbon-carbon interaction change due to high electrical field and increased temperature (electrothermal effect) (Liu et al. 2014 Zhang et al. 2014). Another principle is diffusion of ions and ion pairs induced by applied low potential as shown in Fig. 1. These transducers usually combine carbon materials with polymer matrix and some ionic conducting media. They seem to have much more possible applications in the near future (Asaka et al. 2013). 

In recent several years, super-capacitors are attracting more and more attention because of their high capacitance and potential applications in electronic devices. The performance of super-capacitors with MWCNTs deposited with conducting polymers as active materials is greatly enhanced compared to electric double-layer super-capacitors with CNTs due to the Faraday effect of the conducting polymer as shown in Fig. 9.18 (Valter et al., 2002). Besides those mentioned above, polymer/ CNT nanocomposites own many potential applications (Breuer and Sundararaj, 2004) in electrochemical actuation, wave absorption, electronic packaging, selfregulating heater, and PTC resistors, etc. The conductivity results for polymer/CNT composites are summarized in Table 9.1 (Biercuk et al., 2002). 

In this chapter, recent developments in electrode materials and ionic polymer membranes used for manufacturing IPMCs were reviewed. Although noble metals such as platinum and gold are commonly used for electrodes in water-based systems and applications for their excellent electrochemical properties, also various nonmetallic conductive carbon derivatives are considered as promising alternatives for fabricating dry-type IPMC actuators. These carbon derivatives include nanotubes and nanoporous-activated and carbide-derived carbons. While tiieir electric conductivity... 

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