Integrated by Design: A Hybrid Robotic Palm Fusing a Functionally-Dense Compliant Matrix with an Actuated Skeleton

Abstract

Inspired by the human hand, this work presents a hybrid soft-rigid architecture for a robotic palm to enhance dexterity and robustness. While soft-robotic hands often lack the structural integrity to handle heavy objects, classical rigid designs are sensitive to impacts and frequently neglect the palm's functional role. We bridge that gap by combining soft compliance with skeletal elements for robust force transmission. In our design, rigid metacarpal bones house local actuation and transmission units. These units receive torque from forearm-based motors via flexible shafts to drive tendon actuation. We embed these elements in a 3D-printed silicone matrix, which eliminates the design restrictions of traditional moulding. Ball joints for the thumb and little finger enable the formation of three palmar arches. In experiments, the palm achieved active and passive deformations of 74% and 67%, respectively, relative to its neutral width. This shape adaptability offers practical benefits in confined spaces, where internal palm movements enable new grasping and manipulation techniques previously difficult to achieve with traditional designs.