Enhancing Grasping Capabilities in Stroke Patients Through a Novel Mechanical Design of the Robotic SixthFinger

The Robotic Sixth Finger has been design almost a decade ago aimed at compensating hand grasping abilities in chronic stroke patients. The proposed prototype was designed to be worn on the paretic forearm forming a cooperative grip with the patient's impaired hand. The modular articulated device adapted its structure to the shape of the grasped object. In this paper, we detail the advancements made to the mechanical design of the Robotic Sixth Finger thanks to the experience gained from end-user tests. Main novelties include modifications to the module design, to the tendon routing, and the pulley system. A noteworthy addition is a flexible plastic appendage addressing challenges in the manipulation of cylindrical objects like bottles and jars. Three experiments were conducted to evaluate the updated prototype, focusing on grasp resilience, force distribution analysis, and real-use scenarios. Results indicate a significant improvement in force distribution, eliminating issues of object roll-off during grasping. Additionally, the updated Robotic Sixth Finger enables confident mid-air power grasp operations.