Several types of prosthetics, such as the M finger and the X finger seen below, currently exist to assist finger amputees regain normal function in their lives. These utilize robot mechanisms such as four bar linkages to achieve the motion of normal fingers and can be passive or active.
Figure 1: M finger design (left) and X finger design (right)
The most common finger prosthetics are meant for those who have an amputation just below the proximal interphalangeal (PIP) joint (anatomy seen below). However, just as there are several types of finger prosthetics, there are different varieties of finger amputations, and some are not suitable for the current devices on the market. By collaborating with the Rewire Laboratory (Rehabilitation with Insight from Robotics and Engineering), we have been put in contact with a patient whose amputation is exactly at the PIP joint of his ring finger. This gives rise to the need for a more specialized type of prosthetic finger and is the motivation behind this project. The patient has asked for a finger device that can help him type; therefore this is the primary function of the device we have developed. As a secondary goal, we also included a robustness to the mechanism by giving it a gripping strength.
Figure 2: Anatomy of the hand