Adaptive design and multi–material additive manufacturing of a rigid–flexible lower–limb prosthetic socket featuring shape–performance synergy

The lower–limb prosthetic socket serves as the critical interface connecting the residual limb to the prosthesis for load transfer and mobility restoration. Relying on static geometry and rigid materials, conventional sockets hinder tissue–specific load distribution and cannot accommodate gait–induced mismatches, compromising wearing comfort and functionality. To address these limitations, a quantitative design strategy for rigid–flexible sockets was proposed, leveraging finite element analysis (FEA) to iteratively optimise topology for precise load regulation and soft–tissue accommodation. A multi–material additive manufacturing strategy incorporating continuous fiber reinforcement was tailored to address heterogeneous interface demands and overcome inherent interlayer weakness. Results indicate that the optimised rigid structure effectively redistributed loads toward load–tolerant muscle groups, while the flexible structure mitigated gait–induced pressure peaks by up to 37.1%. The fabrication strategy improved the bonding strength at the heterogeneous interface by 1.5 times and the vertical tensile strength by 8.1 times compared to unreinforced counterparts. Clinical results validated the simulations, showing a 39.7% pressure reduction and superior subjective comfort. Collectively, this study establishes a comprehensive framework for the design, fabrication, and evaluation of rigid–flexible sockets, providing a quantifiable design method for patient–centered rehabilitation devices.