Superior actuation performance and healability achieved in a transparent, highly stretchable dielectric elastomer film

Abstract

Dielectric elastomers widely used for actuation applications (e.g., soft robots, tunable optics) are vulnerable to mechanical damage, so healability is crucial and is associated with the reliability and service lifetime of dielectric elastomer actuators (DEAs). For DEAs, other than healability, simultaneously possessing a superior actuation performance remains a huge challenge. Herein, a highly transparent, extremely stretchable and healable material was developed based on a fluorine-rich poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) elastomer, where a polar dibutyl phthalate (DBP) was used as the plasticizer so that the healing and electromechanical properties were effectively improved and significantly surpassed those of the polymer matrix. After serious mechanical damage, the composite elastomer quickly healed in less than 24 h at room temperature and returned to almost the same state prior to damage due to the strong dipole–dipole interactions and enhanced chain mobility induced by the polar CF₃ groups and plasticizing effect, respectively. Moreover, P(VDF-HFP) with 10% DBP exhibited an extreme stretchability (strain as high as 2000%), high dielectric properties ( = 10.9 at 10³ Hz) and low Young's modulus (0.93 MPa). When used as the dielectric elastomer of a bending actuator, it could provide a bending angle of 24.8° at a given electric field of 25 MV m⁻¹, which is superior to that of the pure matrix (17.7° at 25 MV m⁻¹). Such an outstanding comprehensive performance can potentially address the current challenge of self-healing dielectric elastomers and enable the composite to be used for soft robot, tunable optic and other actuation applications. Moreover, our work provides a promising strategy for fabricating multifunctional soft materials that are tolerant to various operating environments, e.g., those requiring a large deformation, or prone to suffering damage from puncturing, scratching and cutting.