Compressible dielectric elastomer actuators in high hydrostatic pressures: Models and experiments

Dielectric elastomer actuators (DEAs) are an emerging type of soft actuators based on intelligent electroactive polymers. Compared with conventional rigid actuators, DEAs can adapt to extreme hydrostatic pressures without any bulky protective vessels and, therefore, have demonstrated great promises in high-hydrostatic pressure applications such as deep-sea explorations. However, the effects of the enormous hydrostatic compressions on the mechanical and electromechanical coupling properties and electrical breakdown strengths of DEAs remain unclear due to the restrictions in the existing theoretical models and limitations in the experimental techniques developed for DEAs. To bridge these gaps, this paper develops a hydrostatic pressure-coupled DEA model and introduces a series of experimental characterization techniques for accurately quantifying such effects introduced by the hydrostatic pressures. A wide range of hydrostatic pressures up to 105 MPa (close to the hydrostatic pressure in Mariana Trench) are investigated and its effects on the stiffening of the elastomer, reduction of the actuation strain, and increase of the breakdown electric field of the DEAs are reported in both experiments and models. The contributions of this paper can offer guidelines for characterizing the performances of DEAs under high-hydrostatic compressions and for designing the next-generation soft robotic systems for deep-sea applications.