This paper presents a novel conceptional design of a prosthetic finger and its optimization. The finger consists of two phalanges, interconnected by rolling contact joints. A novel conceptual design of the rolling joints is presented that combines the advantages of two previously reported versions, i.e. minor dimensional errors do not result in complete loss of preload and associated backlash, while they guarantee precise positioning as long as the joint load is below the preload. The two phalanges are driven by a single tendon. Consequently, this concept is adaptive, yet underactuated (less degrees of actuation than degrees of freedom). A multibody model of the finger was made, based on a general dynamic model. This paper focusses on the static model that was derived from the general model in order to optimize the dimensional design for uniform force distribution, regardless of size and shape of the object. For the optimization, a genetic algorithm was used. A dimensional design was found that features a standard deviation of the ratio of pinch force to operating force of only 1.2 percent over a range of motion of 60 degrees for each joint.

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