Dielectric Elastomers as Electromechanical Transducers docx

[...]... decreased as the thickness decreased and area increased By contrast, in the constant voltage case, as the film decreases in thickness and increases in area, the field pressure increases to reduce the net stiffness of the film in thickness compression As the thickness of the film increases, however, at constant voltage the field decreases Hence, the effects of the field on mechanical stiffness decrease... VHB based elastomers, respectively The continuous power output of dielectric elastomers also matches or exceeds that of our skeletal muscle, with human muscle producing about 50 W/kg, compared to about 400 W/kg in the elastomers In fact the specific power generated by dielectric elastomers is similar to that of highrevving electric motors These figures of merit are compared in Table 2.1 Overall, dielectric. .. along the chain, thereby preventing the formation of extended domains The resulting electromechanical coupling in the defect containing materials, known as relaxor ferroelectrics, is 10–40% [3] This is not quite as high as is achievable in dielectric elastomers, but is in the same range as muscle As in dielectric elastomers, the coupling needs to be divided by two (or more) to obtain the actual amount... such as film stability and leakage, as well as applied to devices such as sensors and variable stiffness devices that transduce mechanical energy both to and from electrical energy The analysis conveniently uses an energy approach because ideal DEs are lossless, but more realistic energy loss mechanisms such as leakage and viscoelasticity are also discussed Keywords: Actuators, dielectric elastomers, electromechanical. .. PROPERTIES OF DIELECTRIC ELASTOMERS Anne Ladegaard Skov1 and Peter Sommer-Larsen2 1 2 Department of Chemical Engineering, The Technical University of Denmark, Lyngby, Denmark Polymer Department, Risø National Laboratory, Roskilde, Denmark Abstract The basic physical and chemical properties of elastomers are essential for their use in dielectric elastomer actuators The elastic modulus, the dielectric constant,... extent the properties of the resulting elastomer In order to design dielectric elastomer actuators it is necessary to keep in mind the possibilities and limitations of the applied elastomeric material Different aspects of the choice of material as well as the preparation procedure are discussed in the present chapter 3.1.1 Elastomers The empirical definition of an elastomer is a macromolecular material... shape shortly after the load has been released A more physical definition is that an elastomer is a crosslinked polymer material above its glass transition temperature Three common types of elastomers are chemically crosslinked (vulcanized) rubbers, physically crosslinked thermoplastic elastomers, and polymers of sufficiently high chain length, where entanglements serve as physical crosslinks A wealth... seconds to days – viscoelastic response observed in most elastomers Chapter 17 illustrates how viscoelasticity affects the dynamic behaviour of acrylate elastomer actuators The dielectric constant is proportional to the density of polarizable groups and decreases with increasing temperature due to thermal expansion The affine model for rubber elasticity (see below) states that the elastic modulus is proportional... the energy density of batteries is at least 20 times lower than that of sugars and fats used by muscle, meaning that to go the same distance with the same efficiency, 20 ϫ more fuel mass must be carried Cycle life in dielectric elastomers is reasonable, but at ϳ106 for moderate to large strains [3] is still much lower than is possible in muscle itself Dielectric elastomers have two advantages relative... recruitment, regeneration and variable stiffness Dielectric elastomers are not the only materials that actuate in response to applied voltage, producing displacements akin to those of muscle A selection of other technologies are now described and compared to dielectric elastomers The aim is to describe advantages and disadvantages of each relative to dielectric elastomers 2.3 RELAXOR FERROELECTRIC POLYMERS . constant charge case, the field and field pressure of the film decreased as the thickness decreased and area increased. By contrast, in the constant voltage case, as the film decreases in thickness. develop improved muscle-like actuators, dielectric elastomers have also been shown to have great potential for applications as generators and sensors. Dielectric elastomers can potentially replace. of dielectric elas- tomers. This section describes how dielectric elastomers work and how they fit into the larger picture of electroactive polymers. The second section looks at dielectric elastomer