Design of Compliant Components in Linkage-Driven Prosthetic Fingers: A Multi-Material Printing-Based Method

The ability to effectively grasp and hold objects with different shapes is enabled by the hand's capacity to preshape its fingers and adapt them to the object's shape (i.e. preshaping and shape-adaptive behaviour). This work analyzes the 3D-printed prosthetic hand models developed so far and aims to advance the design for additive manufacturing of linkage-driven prosthetic fingers provided with both preshaping and shape-adaptivity. After reviewing the main possibilities enabled by additive manufacturing, the work proposes a method based on multi-material printing to develop mechanically compliant elements that can be effectively exploited in linkage-driven prosthetic hands with preshaping and shape-adaptive behaviour. The proposed method is tested on a specific link and validated using an Instron Universal Testing machine to experimentally identify the best manufacturing parameters. The results achieved, although specific to a particular link, support the feasibility of the proposed approach. This paved the way for the development of reliable and affordable 3D-printed linkage-driven prosthetic hands provided with preshaping and shape-adaptive behaviour.