Advanced robotic hand prostheses are praised for their impressive robust and fine grasping capabilities generated from intricate systems. Nevertheless, a high demand remains for grasping mechanisms that are mechanically simple, lightweight, and cheap to produce, easy to assemble and low in maintenance costs. This paper presents the design of a partially compliant underactuated finger to demonstrate the feasibility of achieving these rigorous requirements. The conceptual topology of the three phalanx finger is selected based on competitive analysis. Employing Pseudo-Rigid Body Model and Finite Element Analysis, a genetic optimization problem is formulated to minimize bending stresses within compliant flexures. The result is a fully functional demonstrator capable of flexing 180° in finger rotation. The prototype is fabricated from flexible high strength nylon and requires no assembly steps beyond 3D printing. Experimental testing verifies the design method with an acceptable error of < 5%.

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