Design, Development and Characterization of a Single-Layer 3D-Printed Strain CB-TPU Sensor

• Published in: Proceedings (IEEE International Workshop on Metrology for Industry 4.0 and IoT. Online) pp. 265 - 270
• Main Authors: Saroli, Vincenzo, Pinnelli, Mariangela, Romano, Chiara, Silvestri, Sergio, Schena, Emiliano, Massaroni, Carlo
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.07.2025
• Subjects: 3D Printing; Additive Manufacturing; Biomedical monitoring; Capacitive sensors; Conductive Filament; Load modeling; Monitoring; Piezoresistance; Production; Sensor phenomena and characterization; Strain; Strain Sensor; Three-dimensional printing; Wearable Sensor; Wearable sensors
• ISSN: 2837-0872
• DOI: 10.1109/MetroInd4.0IoT66048.2025.11121943

Among the various physiological parameters, respiratory rate is undoubtedly one of the most relevant, as it provides valuable information about an individual's physiological state. Despite the wide availability of sensors for measuring this parameter, these solutions are often expensive and complex. Such limitations can be overcome through additive manufacturing techniques, such as 3D printing, which are increasingly being adopted across various fields. Among these, fused deposition modeling (FDM) enables the production of objects with highly complex geometries while reducing costs and allowing for various filament types, each with specific mechanical and electrical properties. The present study aims to design and develop a single-layer 3D-printed strain sensor (with a thickness of 0.15 mm) made of thermoplastic polyurethane loaded with conductive carbon black particles. For electromechanical characterization, quasistatic and cyclic tensile tests were conducted up to a strain of 5%. Achieving this strain requires a tensile force of only 2.4 N, highlighting the sensor's excellent mechanical properties. The relationship between resistance variation and applied strain is nonlinear, with a maximum resistance change of 38% and a gauge factor of -12.4 at 1.5% strain. Regarding cyclic loading/unloading tests, the sensor's output varies consistently with the input even at high frequencies (up to 90 cycles / \mathrm{min}), and the hysteresis error remains remarkably (\lt)5 \% despite the sensor's piezoresistive nature. Finally, a pilot test was conducted on a single subject to assess the feasibility of using the sensor for respiratory monitoring.