Dielectric elastomers actuator parameters

Matysek M, Lotz P, Flittner K, Schlaak HF (2008) High-precision characterization of dielectric elastomer stack actuators and their material parameters. Proc SPIE 6927 692722... 

Koh et al. [6] have rigorously modeled the electromechanics of this interaction for the simplified case of uniform biaxial stretching of an incompressible polymer film including many important effects such as the nonlinear stiffness behavior of the polymer film and the variation in breakdown field with the state of strain. With regard to the latter effect, Pelrine et al. [5] showed the dramatic effect of prestrain on the performance of dielectric elastomers (specifically silicones and acrylics) as actuators. We would expect the same breakdown enhancement effects to be involved with regard to power generation. There are many additional effects that may be important, such as electrical and mechanical loss mechanisms, interaction with the environment or circuits, frequency, and temperature-dependent effects on material parameters. The analysis by Koh provides the state equations... 

In any case, polyurethane dielectric elastomers have continued to be studied in the last decade, particularly with regard to the possibility of increasing their actuation performance. It is well known that both dielectric and mechanical properties are key parameters governing the electromechanical response of any dielectric elastomer, which can be in principle improved by an increase of the dielectric constant and by a decrease of the elastic modulus. In order to increase the dielectric permittivity of a polymer elastomeric matrix, various methods are available (Carpi et al. 2008), such as making composites or blends with highly polarizable phases. Table 1 constitutes a non-exhaustive list of works fi-om the literature, mostly relying on such methods for improving the performance of polyurethane dielectric elastomers. The studies are classified in terms of system complexity and component materials. 

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