Abstract
This study presents a biomechanics-driven approach to develop two-phalanx prosthetic fingers replicating essential human finger motions. A detailed biomechanical analysis of joint trajectories, anatomical constraints, and functional coordination for tasks like grasping identifies key motion features to guide design. Two underactuated prosthetic finger mechanisms are proposed, balancing anatomical realism with structural simplicity. Each employs mechanical couplings and passive elements to achieve coordinated phalanx flexion and extension using minimal actuation, enhancing manufacturability and integration into upper limb prostheses. Kinematic modelling using Denavit–Hartenberg parameters in MATLAB generates motion trajectories and assesses fingertip path accuracy under various actuation conditions. Integrated biomechanical constraints ensure realistic motion ranges and joint coordination. Comparison with natural finger behaviour shows both mechanisms closely approximate intended motion patterns, delivering satisfactory trajectory fidelity, smoothness, repeatability, and reproducibility. These results demonstrate the effectiveness of biomechanics-informed design and hybrid kinematic modelling for practical, anatomically relevant prosthetic fingers and potential for customization of prosthetics.