Design and 3D Printing of Soft Bending Sensors with TPMS Structures

Wearable sensors for health monitoring have gained significant attention, driving demand for innovative designs and fabrication methods. Recent advancements in flexible piezoresistive conductors have opened up possibilities for more effective wearable technology, enhancing both the precision and comfort of body movement monitoring. Incorporating cellular designs with adjustable and controllable porosity, including triply periodic minimal surface (TPMS) structures, into soft piezoresistive sensors shows great promise. These designs provide controllable deformation mechanisms and improved flexibility, enabling mechanical properties to be tailored for different types of body movements. This study presents TPMS-based soft sensor structures engineered for body bending monitoring, utilizing a cost-effective fabrication approach. Soft sensors were fabricated through fused deposition modeling (FDM) 3D printing, utilizing conductive thermoplastic polyurethane with hyperelastic properties. Two unique TPMS porous structures, I-WP and Gyroid, were incorporated in the design. A finite element simulation according to a hyperelastic model was conducted to simulate the mechanical behavior of these structures, and the findings were compared with experimental results. Furthermore, piezoresistive testing under various bending experiments was conducted. The results demonstrated consistent performance and stability under cyclic loading, establishing these cellular TPMS soft sensors as promising candidates for monitoring body bending movements.