Mechanics of dielectric elastomers: materials, structures, and devices

Abstract

Dielectric elastomers (DEs) respond to applied electric voltage with a surprisingly large deformation, showing a promising capability to generate actuation in mimicking natural muscles. A theoretical foundation of the mechanics of DEs is of crucial importance in designing DE-based structures and devices. In this review, we survey some recent theoretical and numerical efforts in exploring several aspects of electroactive materials, with emphases on the governing equations of electromechanical coupling, constitutive laws, viscoelastic behaviors, electromechanical instability as well as actuation applications. An overview of analytical models is provided based on the representative approach of non-equilibrium thermodynamics, with computational analyses being required in more generalized situations such as irregular shape, complex configuration, and time-dependent deformation. Theoretical efforts have been devoted to enhancing the working limits of DE actuators by avoiding electromechanical instability as well as electric breakdown, and pre-strains are shown to effectively avoid the two failure modes. These studies lay a solid foundation to facilitate the use of DE materials, structures, and devices in a wide range of applications such as biomedical devices, adaptive systems, robotics, energy harvesting, etc.

A Portable Real-Time Test Bench for Dielectric Elastomer Actuators

“…Furthermore, viscoelastic effects can be seen in Figure 6, although the compression test was performed with a low deformation rate. These phenomena are consistent with literature information on the deformation of elastomers (compare Figure 3 a) and b)) [11,26]. These results indicate that even in a smaller deformation range, viscoelastic effects should also be considered.…”

“…It should be noted that the deformation described does not happen without dissipation [26]. It leads to time-dependent effects such as hysteresis, creep and relaxation as schematically shown in Figure 3 b)-d) (for c) and d) stimulus in the upper and response in the lower part) [11,26]. Various material models are available to describe the properties of elastomers.…”

“…The change in thickness of the membrane during deformation was not considered. The following models were considered for the passive static description: Hookean, Neo-Hookean [35], Yeoh [36], Gent [37], Ogden [38] and Mooney-Rivlin [11,[39][40][41][42]. For reasons of clarity, the static description does not contain the visualization of the temporal progression.…”

“…The passive part is described using statistical or continuum mechanics. Parameters of the respective structure are determined partly or completely by experiments [8,10,11]. Statistical mechanics are based on Gaussian and non-Gaussian statistics and attempt to explain relationships microscopically [10,12].…”

Self-Healing and Damage Resilience for Soft Robotics: A Review

“…Very high electric potentials (in the range of kV) are often necessary to induce significant shape change, despite the dielectric typically being a thin film (<1 mm). For greater details, the reader is recommended these recent reviews (Wang and Qu, 2016;Zhu et al, 2016;Zhang and Serpe, 2017).…”