Ossicle Reinforced Porous Structure for Variable Stiffness Soft Actuator Inspired From Echinoderms

The variable stiffness capability can broaden the range of applications by providing both the adaptability through conformability inherent in soft robots and the ability to transmit large forces and high payloads in a rigid state. The stiffness modulation ability of compliant-bodied living creatures, according to the tasks, makes them interact efficiently with unstructured surroundings. The design of stiffness–modulation structures and methods, which can be well incorporated with the flexible body of a soft robot, can be informed by animal physiology. This study presents an echinoderm-inspired stiffness-modulation method with a rigid structure reinforced with porous material actuated by vacuum, causing deformation and compressive force. We demonstrate a continuative stiffness change (15-fold increase), and the device is shown to be mechanically programmable. Furthermore, we apply the proposed method to the gripper and robotic paw to demonstrate the advantages of stiffness modulation in the soft robotics. Consequently, it was demonstrated that the stiffness of a soft robot can be increased in situations requiring a higher load-bearing capacity or impact response tuning, while retaining its inherent adaptability.