Bio-Inspired Soft Variable-Stiffness Prehensile Tail Enabling Versatile Grasping and Enhancing Dynamic Mobility

In nature, prehensile tails serve as versatile and essential appendages for animals, facilitating both grasping and enhanced mobility. Although existing robotic tails effectively contribute to mobility across a range of behaviors, they lack versatile object-grasping capabilities. Inspired by these biological capabilities, a soft robotic prehensile tail is presented that uniquely integrates object manipulation with dynamic mobility enhancement for quadrupedal robots. This robotic tail offers a threefold stiffness variation and achieves large-angle bending (${\sim} 636^{\circ }$) at the tail tip, thereby enabling secure and adaptable grasping. By adjusting its stiffness, the tail can conform to various shapes in a soft state and lift objects of different weights in a stiff state, demonstrating versatile grasping. The stiffened tail reliably supports the robot's body load (e.g., when hanging on a rod) and facilitates rapid, precise dynamic adjustments. Moreover, a novel synergy is revealed whereby grasped objects increase the tail's inertial effects, thereby enhancing the robot's dynamic capabilities during rapid maneuvers—a unique feature that transforms manipulation tasks into mobility advantages.