A Prestretch-Free Dielectric Elastomer with Record-High Energy and Power Density via Synergistic Polarization Enhancement and Strain Stiffening

Dielectric elastomer actuators with high energy and power output, combined without pre-stretching treatment to simplify device fabrication, are highly desirable for soft robotics. Here, different from most studies that focus on modifying elastomers such as polyacrylates and silicones, the study designs a prestretch-free dielectric elastomer based on hydrogenated carboxylated nitrile butadiene rubber to reach a record-high energy density (564 J kg −1 ) and power density (5641 W kg −1 ), ≈15 times greater than natural muscle and three times greater than the state-of-the-art dielectric elastomers. This excellent performance arises from the synergistic polarization enhancement and strain stiffening overcoming the inherent trade-offs between electrical and mechanical properties, simultaneously endowing the elastomer with an extremely high dielectric constant ( ɛ r = 17, 100 Hz), ultralow mechanical loss (tan δ m = 0.04@1 Hz), and large electrical breakdown strength (105 V µm −1 ). The assembled 40-µm-thick actuator lifts a 200-g load with over 20% strain and maintains a stable power density of 4780 W kg −1 for 50 000 cycles. Furthermore, the actuators demonstrate diverse applications, including serving as biceps artificial muscles to achieve a 90° rotation angle at a speed of 360°/s and actuating a soft robot carrying a load 20 times its weight. These findings provide a different approach for developing high-performance dielectric elastomers to broaden their application in soft robotics.