Variation: Material

Theoretically every soft, stretchable, insulating elastomer membrane can be used in dielectric elastomer actuators. However, the actuation performance is strongly influenced by the properties of the material. Materials with low stiffness and large fracture stretch often show larger actuation strains than stiff materials. The electric constant of the material determines the size of the Maxwell stress (see Modeling section) and therefore the amount of deformation the actuator undergoes. Materials with large dielectric breakdown strength allow the application of larger voltages and therefore larger actuation strains. On the other hand, viscoelasticity reduces the response time and efficiency of the actuators and these parameters are interconnected in many materials, so a compromise between these parameters has to be found.

The most studied classes of materials for dielectric elastomer actuators are acrylates, silicones and polyurethanes. The properties of exemplary materials are shown in the table below. Acrylic elastomers often have a high dielectric constants and dielectric breakdown strengths, but can have a pronounced viscoelastic behavior that limits the speed of actuation. Silicones usually have lower dielectric constants, but are also less viscous. Polyurethanes are a large class of materials and can have, depending on the formulation, very different properties. By changing the building blocks of the material, the properties of polyurethanes can be tailored to specific applications.

Bibliography

Keplinger et al. (2012) Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation.

Keplinger et al. (2013) Stretchable, transparent, ionic conductors.

Koh et al. (2009) Maximal energy that can be converted by a dielectric elastomer generator.

Wissler and Mazza (2007) Mechanical behavior of an acrylic elastomer used in dielectric elastomer actuators.

Pelrine et al. (2001) Dielectric elastomers: generator mode fundamentals and applications.

Pelrine et al. (2000) High-Speed Electrically Actuated Elastomers with Strain Greater Than 100%.

Röntgen WC. (1880) Ueber die durch Electricität bewirkten Form—und Volumenänderungen von dielectrischen Körpern.

Suo, Zhigang (2010) Theory of dielectric elastomers.

Contributors

Philipp Rothemund