Embodied manipulation with past and future morphologies through an open parametric hand design

A human-shaped robotic hand offers unparalleled versatility and fine motor skills, enabling it to perform a broad spectrum of tasks with precision, power, and robustness. Across the paleontological record and animal kingdom, we see a wide range of alternative hand and actuation designs. Understanding the morphological design space and the resulting emergent behaviors can not only aid our understanding of dexterous manipulation and its evolution but also assist with design optimization, achieving and ultimately surpassing human capabilities. Exploration of hand embodiment has, to date, been limited by challenges of accessibility in customizable hands in the real world and by the reality gap in simulation of complex interactions. We introduce an open parametric design that integrates techniques for simplified customization, fabrication, and control with design features to maximize behavioral diversity. Nonlinear rolling joints, anatomical tendon routing, and a low-degree-of-freedom modulating actuation system enable rapid production of single-piece 3D-printable hands without compromising dexterous behaviors. To demonstrate this, we evaluated the low-level behavior range and stability of the design, showing variable stiffness over two orders of magnitude. In addition, we fabricated three hand designs: human, mirrored human with two thumbs, and aye-aye hands. Manipulation tests evaluated the variation in each hand's proficiency at handling diverse objects and demonstrated emergent behaviors unique to each design. Overall, we introduce diverse designs for robotic hands, provide a design space to compare and contrast different hand morphologies and structural configurations, and share a practical and open-source design for investigating embodied manipulation.