Measurement of Strain on 3D-Printed Foot Prosthesis Using Fiber Bragg Grating Sensors

High-performance foot prostheses are requested to ensure optimal performance and longevity of the device during its use. Monitoring the mechanical performances of a foot prosthesis is important to early identify possible changes that could affect patient health over time. This work aims to evaluate the feasibility of implementing such monitoring using Fiber Bragg Gratings (FBG) based sensing system. The foot prosthesis has been fabricated using the Additive Manufacturing technique based on continuous fiber 3D printing, which allows to product a prosthesis with custom features. This technology relies on the incorporation of continuous carbon fiber into a thermoplastic matrix to produce high-performance products. A single optical fiber equipped with 5 FBGs was glued on a 3D-printed foot prosthesis. The design of the prosthesis and the location of FBG sensors were optimized through Finite Element Simulations. The instrumented prosthesis was tested following ISO standards designed to access its mechanical parameters. Quasi-static tests simulating different gait phases were carried out to estimate the relationship between applied force and strain; cyclic tests were performed to evaluate any potential damage condition. The proposed sensing system based on FBGs was able to detect the material's plastic deformation and the prosthesis's plasticization condition. These results further corroborate the importance of equipping a prosthetic foot with a dedicated monitoring system.