Stiffness enhanced reconfigurable soft hand for versatile stable grasps and in-hand manipulation

Traditional soft robotic grippers often lack the structural rigidity required to maintain stable poses under external forces, as well as the fine control and precision offered by rigid grippers or conventional robotic hands. These limitations are particularly significant in tasks requiring dexterous manipulation, such as in-hand manipulating objects. This paper proposes a bio-inspired spine mechanism capable of self-adapting to the variable length of the finger, thus increasing strength and stiffness without compromising the intrinsic compliance of soft fingers. A passive inflatable soft fingertip design is further introduced to enhance grasp stability. The performance of the proposed soft fingers mounted on a reconfigurable palm is evaluated through stiffness characterization, grasping tests, and in-hand manipulation demonstrations. Experiments show that the spine substantially increases both front and side stiffness and improves grasp stability under dynamic conditions. With the combined advantages of reconfigurable palm mechanism and the adaptive soft fingers, the proposed Soft Reconfigurable Hand achieves robust grasping and stable in-hand manipulations across diverse tasks.