Electromechanical actuators applications

Conducting polymers have found applications in a wide variety of areas,44 45 and many more have been proposed. From an electrochemical perspective, the most important applications46 appear to be in batteries and supercapacitors 47,48 electroanalysis and sensors49-51 electrocatalysis,12,1, 52 display and electrochromic devices,46 and electromechanical actuators.53... 

One of the more fascinating applications is the electromechanical actuation with CPs, leading to artificial muscles, wings, and propellers. The basis behind such actuation is that CPs swell on doping, with an increase... 

Many electrochemically dopant-induced structure-property changes in conducting polymers have been described for use in, for example, electrochromic windows and displays, electrochemically controlled chemical separation and delivery systems, redox capacitors, electromechanical actuators, etc.,32. Some of these are apparently close to commercial application. Polypyrrole capacitors are already in conunercial production,27. 

Relaxor-type electrostrictive materials, such as those from the lead magnesium niobate-lead titanate, Pb(Mgp 3Nb2/3)03-PbTi03 (or PMN-PT), solid solution are highly suitable for actuator applications. This relaxor ferroelectric also exhibits an induced piezoelectric effect. That is, the electromechanical coupling factor kt varies with the applied DC bias field. As the DC bias field increases, the coupling increases and saturates. Since this behavior is reproducible, these materials can be applied as ultrasonic transducers which are tunable by the bias field [12]. 

IPMCs are smart materials that exhibit electromechanical (actuator) and mechanoelectrical (sensor) applications. Table 9.1 shows performance properties of state-of-the art IPMCs [5]. They bend quickly under a low voltage, as first reported by Oguro and his co-workers [6]. Later, Abe et al. introduced the important role of existent counter ions and their influence during the bending [7]. Asaka and Oguro introduced a theory of the actuation mechanisms [8] Shahinpoor and Kim demonstrated that the ionic polymer actuator performance depends on the type of cation [9] and further developed a two-step fabrication method [10] in accordance with their findings. In addition, other groups tried to incorporate various metals as electrode materials to articulate physical properties or electrical responses [11-14]. 

For electromechanical and actuation applications, the following parameters are critical maximum electric-induced strain response (Xm), block force (Fb) and elastic energy density, including the volumetric elastic energy density (Wy) and gravimetric elastic... 

The first item restricts the exploitation of the analogy to the case of actuator applications and thus excludes sensor applications. Although the second item is not reflected in the constitutive relation, the usual treatment of the temperature in finite element codes confines such a simulation of electromechanical coupfings to the static case. By virtue of the third item, it is dealt with a different nmnber and arrangement of constitutive coefficients, but this fact does not cause any restrictions and can be handled by the subsequently described substitution. The mechanical constitutive relation of the general anisotropic case, given by Eq. (4.1), can be extended to thermal influences with the aid of the vector of thermal expansion and shear coefficients a and the thermal gradient AT ... 

Cameron CG, Underhill RS, Rawji M et al (2004) Conduetive filler - elastomer composite for Maxwell stress aetuator applications. Proc SPIE 5385 51-59 Carpi F, De Rossi D (2005) Improvement of electromechanical actuating performances of a silicone dielectric elastomer by dispersion of titaniirm dioxide powder. IEEE Trans Dielectr Electr Insul 12 835-843... 

CNTs are also widely used in actuators [168-171], The addition of CNTs to PANI fibers increased the electromechanical actuation because the CNTs improved the mechanical, electronic and electrochemical properties of the PANI fibers [172-174], Composites based on CNTs are studied for a variety of sensor applications [175-177], For example, polypyrrole or PANI deposited on single-walled CNT networks that can be used as solid state pH sensors [178], A DNA sensor was created fi om a composite of polypyrrole and CNTs fimctionalized with carboxylic groups to covalently immobilize DNA onto CNTs [179], In general, the presence of CNTs tends to increase the overall and selectivity of biosensors, The thermal transport properties of polymer composites can be improved with the addition of CNTs due to the excellent thermal conductivity of CNTs, Such composite are quite attractive for usages as printed circuit boards, connectors, thermal interface materials, heat sinks, lids, housings, etc, [92,180],... 

Indeed, the titles and subjects in the PART II APPLICATIONS section of this book -Batteries, Light Emitting Diodes, Sensors, E/0 Dences, Microwave Attenuation, Electrochromics, Anti-Corrosion, Electromechanical Actuators, lithography. Catalysis, Drug Delivery, Membranes- speak for themselves in this respect. They show the astoundingly wide applications of these unique polymers. 

More futuristic applications for conducting polymers that are receiving considerable attention include electromechanical actuators (artificial muscles). Allied Signal (now Honeywell International) is interested in the development of lower power/voltage moving parfs for micromachined optical devices. NASA has also been involved in the development of low-power lightweight actuators for the window wiper on the Mars Explorer. 

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