Bioinspired Soft Tube-Foot Array With Variable Stiffness: Design, Characterization, and Application

Soft array structure has the advantages of super redundancy, high fault-tolerance, high adaptability, and high reliability, and has a promising application in soft grasping, soft locomotion, and interface science. However, the variable stiffness of soft array structures has always been challenging. Inspired by the biological tube foot and water vascular system of starfish, we propose a fiber-reinforced soft fluidic tube-foot array with variable stiffness. The soft tube-foot array can be assembled on various shapes of surfaces and can be modularized, enabling the functions of self-adapting, cushioning, variable damping, and obstacle surmounting. Furthermore, we build a peak stiffness model for the bioinspired tube foot, and the theoretical and experimental comparison results show that the mean absolute percent error is ≤9.3%. Finally, we apply the soft tube-foot array to the soft grasping and amphibious wheels. The contribution of this work is to propose a novel soft array structure and a simple and universal method to control the stiffness of fluid-actuated soft array structures.