Bioinspired Soft Actuators for High Bending Stiffness and Flexible Spatial Locomotion

Soft pneumatic actuators often struggle to achieve both a high degree of freedom and high bending stiffness simultaneously. In this study, we present a bionic soft pneumatic actuator inspired by the intricate musculature of the elephant trunk, which employs a dual actuation mode of transverse-longitudinal muscles to enable flexible spatial motion. By synergistically combining three different elastic materials, the bionic soft pneumatic actuator achieves a unique structure and control method, enabling unparalleled spatial locomotion with bending motion in eight different directions. Theoretical analyses and experimental results demonstrate that the folded structure with square spaced surfaces, in conjunction with pneumatic artificial muscles (PAMs), exhibits superior performance. It achieves a deformation stiffness of 500 mN/mm while maintaining a bending angle of 40°, which is more than twice that of conventional actuators. With the flexible spatial movement ability, it can be applied to flexible manipulators, adapting to the gripping of objects of different shapes and qualities, and realizing the gripping of objects with a maximum weight of more than 1000 g. This flexible actuator integrated with material, structure, actuation, and control provides a new direction for the application of bionic soft robots.