A Manually Actuated Robotic Supernumerary Finger To Recover Grasping Capabilities

The Robotic Sixth Finger is a wearable aid that has been developed to recover grasping capabilities in patients with a reduced mobility of the hand, usually after a stroke. The finger and the paretic arm act as the two jaws of a gripper to restrain the motion of an object. In this work, we present a novel version of the Sixth Finger that is completely free of any electronic component and that can be manually actuated. This solution reduces drastically the cost of production while increasing the intuitiveness of the control and use. The prototype includes an a 3D-printed strong and compact ratchet mechanism. We also explore the possibility of using the Sixth Finger to assist not only stroke patients but, more in general, everyone that have lost grasping capability to one hand, such as amputees or spinal cord injury patients. We propose this simple and low cost prototype as an alternative to prosthesis or as an aid for activities of daily living in developing countries and in world zones where classical prosthesis or rehab facilities are rarely accessible. To demonstrate the usability of the device, ten subjects simulating an amputation or a deficit in hand motion tried the supernumerary finger by completing a modified version of the box-and-block test.