A bimodal-network dielectric elastomer enabling large and stable deformation under low electric fields for soft grippers

Dielectric elastomer actuators (DEAs) have great potential in the field of soft robotics due to their exceptional energy conversion capabilities. However, current dielectric elastomers (DEs) only achieve substantial deformation under high electric fields or near breakdown conditions, severely limiting their practical applications. Here, we propose a novel approach by copolymerizing a self-made small-molecular crosslinking agent (HI₂) with the monomer lauryl acrylate (LA) and the macromolecular crosslinking agent (CN9021NS) to form a bimodal network elastomer. This strategy enables the synthesis of an easily processable dielectric elastomer which has large and stable actuation strain under low electric fields. The incorporation of HI₂ not only reduces the activation electric field of the elastomer but also exhibits an approximately linear relationship between actuation strain and electric field during voltage application. Research indicates that the elastomer CLH-2 exhibits optimal comprehensive properties at 4% HI₂ content, with an “activation deformation” of 5% at 7.95 kV·mm⁻¹ and a maximum actuation strain of 40.96% at 22.36 kV·mm⁻¹. Furthermore, a soft gripper based on the CLH-2 elastomer achieves a large bending angle of 90° at an ultra-low electric field of 9 kV·mm⁻¹. When integrated with a robotic arm, it enables effortless grasping and transfer of objects of varying sizes and weights.