Evaluation of Reproducibility in 3D-Printed Strain Sensors Manufactured by Fused Deposition Modeling

Fused deposition modeling (FDM) 3D printing has gained significant attention due to its advantages, such as rapid prototyping, customization, low cost, and the ability to produce flexible sensors with complex geometries. In this context, sensors reproducibility emerges as a key requirement, since only sensors that consistently exhibit comparable performance can ensure accurate and reliable measurements. This aspect is particularly crucial in biomedical and industrial applications, where the lack of reproducibility may compromise data comparability, hinder calibration procedures, and ultimately limit the translation of 3D-printed sensors from laboratory prototypes to real-world deployment. Despite its importance, reproducibility has received limited attention in the literature, leaving a significant gap that must be addressed to fully exploit the potential of FDM technology. This study presents the design, fabrication and metrological characterization of single-layer bare strain sensors (BS), investigating FDM-printed strain sensors made of thermoplastic polyurethane (TPU) loaded with conductive carbon black (CB). Three configurations were tested as bare (BS), tape-integrated (TS), and silicone-integrated (SS), with three samples each. Metrological characterization included quasi-static tensile and cyclic tests at different frequencies. Calibration curves showed very low standard deviations (