Projects

Fabrication of elastomer composites and compounds

Subproject (BMBF) within the scope of CANDELA – Composite-based new dielectric elastomer actuators

Vollpolymerer dielektrischer Polymeraktor für aktorische Charakterisierung
© Fraunhofer IWS Dresden

Vollpolymerer dielektrischer Polymeraktor für aktorische Charakterisierung

Composite-based new dielectric elastomer actuators (CANDELA)

This research project aims at the development of new functional materials for dielectric elastomer actuators. Special nano-composites, based on dielectric elastomers, are to be used, which guarantee the desired characteristics both of the electrodes and the dielectrics while maintaining maximal compatibility of the applied materials.

Task

CANDELA
© Fraunhofer IWS Dresden

CANDELA

Dielectric elastomer actuators are electrically active polymers and are not only used as actuators, but can also function as sensor systems or energy converters. The commercially available dielectric elastomer actuators consist of a polymer dielectric and two electrode coatings that are made either of thin metal films, sprayed-on conductive particles, pastes, varnishes or conductive polymers. These different coatings have various mechanical properties, which affect both actuator performance and life time.

The objective of the research project was to engineer new functional materials for dielectric elastomer actuators. For these materials, in turn, special nano-composites basing on dielectric elastomers, are to be used: they have to safeguard the desired properties both of the electrodes and the dielectric, at simultaneously maximal compatibility of the materials used.

Solution

The solution is based on a fully polymeric monolithic structure of the dielectric elastomer actuators. This is achieved by modifying a basic polymer according to the required coating properties. Consequently, the layer structure created this way predominantly consists of the basic polymer and individual, mechanically aligned coatings.

Results

REM-Aufnahme eines kryogebrochenen vollpolymeren dielektrischen Elastomeraktors
© Fraunhofer IWS Dresden

REM-Aufnahme eines kryogebrochenen vollpolymeren dielektrischen Elastomeraktors

In material and technology development, it was possible to show that a fully polymeric monolithic dielectric actuator can provide promising results. The material parameters of the individual coatings could be set and adjusted deliberately and reproducibly. The manufacturing technology engineered is suitable for widely differing geometric systems; it can also be employed to fabricate thin coatings. These polymer coatings are thicker than those achieved by sputtering, on the one hand. On the other hand, if the mechanical properties are adjusted, then the influence of the coating thickness can be reduced significantly. In the lab test, coating thickness values of about 20 µm were achieved, and these values can be reduced much more by technological optimization.

The fully polymeric dielectric elastomer actuators provided outstanding results in their role as an actuator. The IWS team was able to show that a decrease in both the coating thickness and the Young’s modulus of the dielectric coating positively affects the performance as an actuator, and thus, confirms the theoretical fundamentals of the dielectric elastomer actuators. The dielectric elastomer actuators produced are also characterized by a very low defect density (Figure 2), so that the layer structures are characterized by “high reliability” of more than 1 million cycles without optical or function-relevant impacts.

The “CANDELA“ research project was performed within the scope of the BMBF (Federal Ministry for Research and Technology) under the registration code 13 N 10660.