Ionic liquid-modified dielectric elastomer composite: Achieving large actuation strain and ultrahigh energy density under low electric field

Dielectric elastomer actuators (DEAs) with large actuation strain as well as high energy and power densities are highly desired for application in soft robotics. Meanwhile, the driving electric fields for DEA are in urgent needs to be further reduced for both safety and energy-efficient concerns. In this work, we develop a modified interpenetrated polymer network (IPN) with specifically designed ionic liquid (IL). The acrylic anion of IL ensures its good compatibility with the polyacrylate matrix for achieving both high dielectric constant (11.82@10 Hz) and low stiffness (0.24 MPa); the low ionicity of IL makes it difficult for cations and anions to separate under an external electric field for achieving a desirable breakdown strength (42 V/μm). As a result, the IL-modified IPN composite exhibits a maximum actuation area strain of 180 % under a low driving electric field of 35 V/μm with no aids of rigid frames. This free-standing DE is further patterned into an anisotropic film by a second stripe-crosslinking treatment, and the obtained DEA achieves an ultrahigh energy density of 455 J/kg—at least 8-fold higher than natural muscles, and power density of 3640 W/kg at only 24 V/μm. Soft robot has been verified which achieves a fast running-speed of 7.13 BL/s. These findings provide a new solution to develop high-performance dielectric elastomers that are closer towards practical application in soft robotics.