Fused Deposition Modeling (FDM) has promised to revolutionize the fabrication of strain sensors, offering design flexibility and cost-effectiveness. However, printing flexible thermoplastic elastomers with conductive nanomaterials presents challenges, such as nozzle blockages and inconsistent feeding due to high melt viscosity and filler agglomeration. In this study, hybrid thermoplastic polyurethane (TPU) nanocomposites filaments containing carbon nanotubes (CNT), graphene nanoplatelets (GNP), and boron nitride (BN), were developed. The hybrid fillers reduced the filament extrusion force and improved the printability compared to CNT-only composites, while maintaining high electrical conductivity and strain-sensing capabilities. A novel extrusion force testing method was implemented to measure the printability of the nanocomposite filaments. The printed sensors, prepared via FDM, demonstrated an enhanced strain-sensing range and mechanical durability, with TPU-CNT-BN composites achieving sensing up to 250% strain. These findings highlight the potential of hybrid nanocomposites for reliable and scalable production of flexible strain sensors using FDM, offering applications in wearable electronics and structural health monitoring.
Soul et al. (Mon,) studied this question.