A Body-Powered Wrist-Driven Supernumerary Robotic Finger

Individuals with grasping impairments face significant challenges in performing daily tasks due to reduced hand function. Existing supernumerary robotic fingers (SRFs) often rely on electronic components that limit their usability through added weight and power constraints. This work introduces the first body-powered wrist-driven SRF (bpSRF), a design that addresses these limitations by removing all electronic components. The proposed bpSRF weighs 52 g and is mostly made of 3D printed parts. Using body-powered actuation principles, the extra finger is driven by wrist movements, offering a practical, affordable, and lightweight solution for hand augmentation. The bpSRF has two degrees of freedom, enabling users to perform enhanced grasping techniques with minimal learning curve. Experimental validation with five healthy participants showed high success rates and rapid learning of novel grasping patterns for tasks involving large or multiple objects that typically require two hands. The design offers a workspace volume approximately three times larger than a human thumb, potentially expanding users' manipulation capabilities. This research contributes to a new paradigm in assistive technology, presenting a lightweight, cost-effective, and open source SRF that can enhance grasping abilities for individuals with motor impairments while also offering augmentation possibilities for healthy users.