Combining fiber-reinforced DEAs with buckling beam system for a soft robotic fish

Soft robotics provides a promising approach for underwater exploration by enabling devices that replicate the fluid movements of aquatic life. Dielectric Elastomer Actuators (DEAs) are well-suited for this application due to their high energy density, fast strain rate and silent operation. However, the integration of these typically planar actuators into complex, three dimensional shapes, e.g., for biomimetic robots, remains challenging. This work proposes a robotic fish design that utilizes fiber-reinforced uniaxial DEAs coupled with a pre-compressed buckling beam. The fiber reinforcement allows actuators to be fabricated with curved cross-sections, enabling their direct integration as the robot's outer skin. Additionally, this reinforcement leads to higher electroactive forces compared to isotropic DEAs. To counteract the additional stiffness from the fibers, a negative-stiffness buckling beam is used to mimic the fish’s flexible spine. This design results in a highly compliant robot capable of large-amplitude fin displacements, demonstrating a practical pathway for creating three-dimensional soft robotic fishes.