Dielectric elastomer generators (DEGs), as a recent transduction technology, harvest electrical energy by scavenging mechanical energy from diverse sources. Their performance is affected by various material properties and failure modes of the dielectric elastomers. This work presents a theoretical analysis on the performance of a dielectric elastomer membrane generator under equi-biaxial loading conditions. By comparing our simulation results with the experimental observations existing in the literature, this work considers the fatigue life of DE-based devices under cyclic loading for the first time. From the simulation results, it is concluded that the efficiency of the DEG can be improved by raising the deforming rate and the prescribed maximum stretch ratio, and applying an appropriate bias voltage. However, the fatigue life expectancy compromises the efficiency improvement of the DEG. With the consideration of the fatigue life, applying an appropriate bias voltage appears to be a more desirable way to improve the DEG performance. The general framework developed in this work is expected to provide an increased understanding on the energy harvesting mechanisms of the DEGs and benefit their optimal design.

As a recent application of dielectric elastomers (DEs), DE resonators have become an alternative to conventional silicon-based resonators used in MEMS and have attracted much interest from the research community. However, most existing modeling works for the DE resonators ignore the intrinsic viscoelastic effect of the material that may strongly influence their dynamic performance. Based on the finite-deformation viscoelasticity theory for dielectrics, this paper theoretically examines the in-plane oscillation of a DE membrane resonator to demonstrate how the material viscoelasticity affects the actuation and frequency tuning processes of the resonator. From the simulation results, it is concluded that not only the applied voltage can change the natural frequency of the resonator, but also the inelastic deformation contributes to frequency tuning. Due to the viscoelasticity of the material, the electrical loading rate influences the actuation process of the DE resonator, while it has little effect on the final steady frequency tuned by the prescribed voltage within the safety range. With the consideration of the typical failure modes of the resonator and the evolution process of the material, the tunable frequency range and the safe range of the applied voltage of the DE membrane resonator with different dimension parameters are determined in this work, which are found to be dependent on the electrical loading rate. This work is expected to provide a better understanding on the frequency tuning of viscoelastic DE membrane resonators and a guideline for the design of DE devices.

As a category of soft electroactive materials, dielectric elastomers (DEs) show great potential for the development of tunable oscillators and resonators for actuating and sensing purposes. However, the dynamic performance of these DE-based vibration devices could be very susceptible to external environment (external loads and excitations) and material viscoelasticity of the DEs. Based on the finite-deformation viscoelasticity theory, this work first investigates the frequency tuning process of a viscoelastic DE membrane oscillator. A comparison of the frequency tuning process and the tunable frequency range between a viscoelastic and a purely elastic DE oscillator is presented. Moreover, particular considerations have been given to the nonlinear response of the oscillator to external harmonic excitation. It is found that the displacement transmissibility of the oscillator can also be actively tuned by changing the static voltage applied to the DE membrane. Under harmonic excitation, various vibration patterns of the oscillator could be actively achieved with the application of both static and alternating electric voltage. Simulation results in this work demonstrate that the material viscoelasticity has a significant effect on the electromechanical coupling and the dynamic performance of the DE-based vibration devices.

As a new transduction technology, dielectric elastomer generators (DEGs) are capable of converting mechanical energy from diverse sources into electrical energy. However, their energy harvesting performance is strongly affected by the material viscoelasticity. Based on the finite-deformation viscoelasticity theory and the nonlinear coupled field theory for dielectric elastomers, this work presents a theoretical framework to model the performance of DEGs. Motivated by the recent experiments of DEGs with a triangular harvesting scheme, we propose a method to optimize the harvesting cycle, which could significantly improve the conversion efficiency of viscoelastic DEGs. From our simulation results, choosing a higher voltage power source appears to be an effective way to improve the performance of DEGs. In addition, optimizing the period of the discharging process of DEG can markedly increase its efficiency. Also, we have uncovered that the triangular harvesting scheme for DEGs, which is expected to harvest energy close to the maximum achievable energy, could be actually realized by choosing dielectric elastomers with a higher fraction of time-independent polymer networks. The theoretical framework and simulation results presented in this work are expected to benefit the optimal design of DEGs for different applications.