Dielectric elastomer actuators (DEAs) are a class of electrostatic actuators that have promising applications in fields like sensors, soft-robotics, microfluidics, and energy harvesting. The crucial points in the working principle of DEA are the application of high electric field and the use of compliant electrodes. These electrodes are typically composed of a mixture of a soft polymer base filled with highly conductive particles. In this work, we show that the charged impurities, possibly present in the electrodes composite, in combination with a high electric field can cause the formation of polarization interface layers between the electrodes and the inner dielectric. These layers can, in the long term, diminish the actuation performance of the DEA.

Dielectric elastomers (DE) have lately drawn attention for their use in soft actuators and electromechanical energy harvester. Excellent dielectric properties and high mechanical deforming capability are key requirements of DEs. Given that the output strain of DE system is proportional to the applied electric field squared (and vice versa), - high electric field is needed to generate large displacement. Similarly to any other insulation exposed to high electric field, DEs undergo electrical ageing. Furthermore, DEs undergo continuous mechanical deformation during its lifetime. Therefore, the lifetime of DE system can be shortened by the simultaneous action of electric and dynamical mechanical stress. This can lead to a faster overall ageing of DE system with respect to other common HV devices, that usually are mechanically-static. To extend the useful life of the system it is firstly important to know how fast the electromechanical degradation process is and what is the contribution of electrical and mechanical stresses. Secondly, assess its ageing stage and adjust its output accordingly, albeit with a lower effectiveness. Partial discharge testing has been used to assess the health of a silicon polymer elastomer typically used in dielectric elastomer generator. The mechanical ageing of a DE system has been qualitatively evaluated by monitor PD activity over different cycles of usage and reported in this paper.