Fiber Bragg Grating Sensors for Mechanical Health Monitoring of a 3D Printed Foot Prostheses

Energy Storage and Return (ESAR) prostheses are widely used for their ability to store and release energy during gait, effectively replicating natural walking dynamics. However, assessing their structural integrity over time remains a challenge. This study introduces a monitoring system based on Fiber Bragg Grating (FBG) sensors integrated into a 3D-printed foot prosthesis to evaluate its mechanical response under cyclic loading. The tests simulated the three main phases of the gait cycle: heel-strike, mid-stance, and toe-off. Strain data from FBG sensors were analyzed to identify key metrics for detecting structural changes. The analysis focused on data from the FBG sensor placed in the heel area, which experienced the greatest impact from cyclic loading. Five strain-based metrics were computed for each cycle, while data from the loading machine were used to determine a parameter accounting for the prosthesis's structural degradation. To assess the reliability of these metrics, correlation and repeatability analyses were conducted between strain measurements and values of the structural degradation parameter. The results were combined into a final score to evaluate each metric's effectiveness in monitoring prosthetic degradation. The findings revealed that some selected metrics demonstrated high correlation and repeatability. These results demonstrate the potential of FBG sensors for real-time monitoring of foot prostheses, providing a valuable tool for predictive maintenance and enhanced patient care.