Bioinspired auxetic metamaterial liners and sockets for transtibial prostheses: Energy absorption and stress redistribution

Prosthetic comfort depends on how the residual limb, liner, and socket share load. A crab-inspired auxetic metamaterial is introduced and applied to transtibial liners and sockets, with region-specific and fully auxetic variants benchmarked against conventional interfaces. Patient CT/3D scans guided anatomically targeted components. Auxetic lattices were additively manufactured in TPU (liners) and PA-12 (sockets). Cyclic compression experiments calibrated material models, and finite-element analyses quantified interface stresses and energy metrics. Across four sensitive liner regions, a four-zone auxetic TPU liner cut peak von Mises stresses by up to 60 %, and a fully auxetic liner by up to 65 %, relative to silicone/EL50 baselines. In sockets, a PA-12 design with two auxetic zones reduced peak stresses by ∼40-45 % versus ABS, while a fully auxetic socket achieved ∼80 % reductions with higher specific energy absorption. These findings indicate that bioinspired auxetics, integrated where anatomy needs compliance, improve pressure redistribution and mass-efficient energy management. The workflow from imaging to lattice design, printing, testing, and simulation was validated and is compatible with multi-jet fusion, enabling patient-specific prosthetic interfaces suitable for clinical translation.