SBIR-STTR Award

Biomimetic Slope Adaptive Foot-Ankle Prosthesis This project will develop an innovative mechanical/hydraulic foot-ankle system that will help lower extremity prosthesis wearers to walk or run in a wider range of environments with close to normal walking biomechanics. The proposed system will have a unique combination of features, all mechanically implemented without electronics or external power: The foot/ankle alignment will adapt the end of ankle motion (i.e., the dorsiflexion stop) to sloped walking surfaces on every step of walking and without delays. A near-normal range of hydraulic ankle motion improves comfort and stability, providing customization of plantar and dorsiflexion resistance. Utilizing well-proven carbon fiber footplates, the foot will provide near-normal energy storage and return during walking. The split-toe feature provides multi-axial compliance, for stability and comfort on non-level ground. A unique toe-lift spring ensures toe clearance during swing phase, for stability and safety. With an integrated and robust design, the foot-ankle system that results from Phase 2 and 3 can be highly water and dirt resistant, allowing use in a very wide range of environments compared with most available feet.

The primary objective is to develop a commercially-viable prototype of the slope adaptive prosthesis design and to iteratively improve the design based on ISO standards testing and rigorous use in human subject field trials. The proposed work will build upon knowledge gained in Phase I of the project, which established feasibility for this design approach in a lightweight, passive hydraulic foot-ankle system. The Biomimetic Slope Adaptive Foot developed in this project seeks to mimic the physiologic ankle by storing energy sooner in the gait cycle, setting the equilibrium point at foot-flat instead of mid-stance, which allows energy to be stored over a larger range of motion and released to the user during unloading. This is expected to provide a greater amount of energy storage and return. Current non-powered (passive) foot-ankle prostheses cannot adapt or change alignment to different terrain during walking. They are less stable than an articulated ankle, which can reach foot-flat very soon after heel strike. The proposed foot will have automatic slope adaptation through hydraulic ankle articulation. The purely mechanical system, without battery pack or electronics, will be inherently more rugged and robust, meeting the needs of active prosthesis wearers, whether service members, veterans or civilians.