Dielectric elastomer transducers consist of thin electrically insulating elastomeric membranes coated on both sides with compliant electrodes. They are a promising electromechanically active polymer technology that may be used for actuators, strain sensors, and electrical generators that harvest mechanical energy. The rapid development of this field calls for the first standards, collecting guidelines on how to assess and compare the performance of materials and devices. This paper addresses this need, presenting standardized methods for material characterisation, device testing and performance measurement. These proposed standards are intended to have a general scope and a broad applicability to different material types and device configurations. Nevertheless, they also intentionally exclude some aspects where knowledge and/or consensus in the literature were deemed to be insufficient. This is a sign of a young and vital field, whose research development is expected to benefit from this effort towards standardisation.

No abstract

The focus of this paper is on the modeling of dielectric elastomer actuators and generators. One of the effects that is rarely considered in modeling of these systems is the influence of the materials' specific resistance on the performance. The non-ideal electrical properties of both elastomer and electrode material will cause undesired parasitic effects. Although for most laboratory scale prototypes these effects are hardly recognizable, they may however play an important role for larger structures and especially for dynamic applications. Therefore, an analytical model is developed and presented in this paper which can give helpful instructions for the design and fabrication process of EAP-systems. It is proven to be valid by means of the finite element method and subsequently extended for more complex systems.

Conventional loudspeakers are often heavy, require substantial design spaces and are hard to integrate into lightweight structures (e.g., panels). To overcome these drawbacks, this paper presents a novel extremely flat loudspeaker which uses dielectric elastomer actuators with natural rubber for the elastomeric layers and metal electrodes as transduction mechanism. To facilitate the deformation of the elastomer, the electrodes are perforated. The microscopic holes lead to a macroscopically compressible stack configuration despite the elastomer incompressibility. The design is developed and the materials are chosen to guarantee low mechanical and electrical losses and a high efficiency in the entire frequency range up to several kilohertz. The loudspeaker was designed, built and afterwards experimentally investigated and characterised. Laser measurements of the surface velocity were performed to find dynamic effects present at the diaphragm. To further characterise the device, a semi anechoic chamber as used. Sound pressure levels emitted by the device were recorded at different bias and alternating voltages to study their influence. The nonlinearity of the loudspeaker, which is inherent for this kind of actuators, was quantified considering the total harmonic distortion. Here, a dependence on the amplitude of the alternating voltage is observed. Further, the distortion decreases rapidly the higher the frequency is, which qualifies the loudspeaker concept to properly work at high frequencies. Transfer functions between supplied voltage and on-axis sound pressure were measured and showed in principle potential for high frequency application. Further, the behaviour of the diaphragm changing from rigid piston to resilient disk with respect to frequency for different configurations was observed. Additionally, the directivity of the loudspeaker was investigated at several frequencies, and was in accordance with previously found research outcomes. The results, especially in the high frequency range, prove the usability of this design concept for practical applications.

Dielectric elastomer (DE) actuators could have great potential for innovative solutions in different applications due to their large deformation capabilities, low cost and lightweight nature. One of the main technical challenges in the development of DE actuators is to realize highly conductive, compliant electrodes that do not constrain the large strain of the elastomer material. Metal electrodes are normally not feasible due to their high stiffness, though their electrical properties are excellent. Therefore mostly powder or grease electrodes have been realized so far, yielding good results in the laboratory. However, for many applications in industrial use, stack actuators with compliant electrodes have some disadvantages regarding processing and durability. Additionally the inhomogeneous strain distribution along the stack due to boundary constraints leads to performance losses, especially for thin actuators. Therefore a new design approach with rigid, perforated metal electrodes is chosen. This stack actuator only contracts in one direction whereas all the other directions remain undeformed. To find an optimal electrode design, a numerical model is set up for a small cut-out element of the actuator and different physical effects are subsequently taken into account to match reality as closely as possible. Finally, a functional demonstrator is built and characterized experimentally. The studies show the great potential for elastomer actuators with perforated, rigid electrodes and also demonstrate the need for a careful design and the advantage of numerical optimization methods.