A Multi-Material, Anthropomorphic Metacarpophalangeal Joint With Abduction and Adduction Actuated by Soft Artificial Muscles

In recent years, the field of hand prosthetic research has seen anthropomorphic designs that make use of hybrid soft-rigid materials, combining the load-bearing capability of rigid skeletons with the robustness and mobility of soft materials. This approach generates potential for more advanced prosthetics, yet there are unexplored opportunities for leveraging soft actuation and joint interfaces towards creating more versatile joints. In this work, we present a multi-material metacarpophalangeal (MCP) joint that uses a rigid skeleton and soft ligaments, with the addition of novel soft actuators for active ab/adduction and soft cartilage-lubricant for smoother motion. To support the joint’s potential applications in more dexterous prosthetics, we perform experiments to demonstrate its (1) near linearity in positional control (2) positional repeatability (3) and force output repeatability. We also find that the addition of the novel cartilage-lubricant combination improves the joint’s dynamic response.