Design of 3D printable prosthetic foot to implement nonlinear stiffness behavior of human toe joint based on finite element analysis

Abstract

Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function.

Biomechanical Impacts of Toe Joint With Transfemoral Amputee Using a Powered Knee-Ankle Prosthesis

“…Human toe joint stiffness is shown as a nonlinear trend during walking. Studies such as Um et al ( 2021 ) have proposed using toe-joints with nonlinear stiffness. Future efforts will be directed at studying the performance of transfemoral prostheses with nonlinear stiffness toe-joints.…”

Revolutionizing Prosthetic Design with Auxetic Metamaterials and Structures: A Review of Mechanical Properties and Limitations

“…Later on, the same authors conducted another research work focused on providing an additional mechanism to the lower-limb prosthetic [ 33 ]. This innovation is located in the toe part of the prosthetic to provide a unique nonlinear stiffness behaviour for the prosthetic.…”

“…The ankle part remains constrained in place. A total of 1000 N of force is applied in the direction normal to the inclined part to simulate the weight of an average human male with 100 kg of weight [ 33 ]. The results of the proposed design were then compared with the toe-torque of humans during toe-off.…”

“…Each study has been generally described in the reference provided in Section 2 regarding the state-of-the-art methods for auxetic implementation in a prosthetic. This section will cover more detail regarding the limitation and comparison of the described research [ 9 , 26 , 32 , 33 , 39 ]. The auxetic single-layer liner studied by Brown et al was mainly conducted using the FEA method.…”

“…For validation, this optimized design was then compared to the human gait data. From the graph shown ( G ), it is concluded that the optimized design shows a good agreement in mimicking the behaviour of the natural human toe [ 33 ].…”