Characterization of Electrically Conductive Polymers Integrated in Additively Manufactured Parts for Sensing

Additive Manufacturing (AM) technologies enable the layer-by-layer fabrication of complex geometries with advantages such as cost-effectiveness, waste reduction, and design flexibility. Among polymer-based AM techniques, fused deposition modeling (FDM) is widely used due to its affordability and ease of use. The demand for high-performance materials has led to the development of polymer matrix composites (PMCs), including conductive polymer composites (CPCs), which integrate electrically conductive fillers within a polymeric matrix. CPCs, particularly those with carbon-based fillers, offer promising applications in sensing devices and 3D-printed electronics. This study investigates commercial CPCs for strain sensing applications, focusing on the impact of sensor track width and temperature on functional performance. Two CPCs are analyzed: a graphite-filled TPU-based CPC (Fili) and a carbon-black-filled TPU-based CPC (FilaFlex Conductive). The materials are co-printed on PLA-based substrates using a dual-extruder FDM process. Tensile tests reveal that graphite-filled CPCs exhibit a strong linear piezoresistive response, while carbon-black-filled CPCs show lower strain sensitivity. Additionally, thermal characterization demonstrates that both CPCs exhibit a positive temperature coefficient (PTC), though matrix-filler interactions influences their response at higher temperatures. The results indicate that graphite-based CPCs are suitable for strain sensing due to their linear piezoresistive behavior, while carbon-black-filled CPCs maintain electrical stability under mechanical deformation. These findings provide valuable insights for selecting CPCs in sensor applications and highlight the need for further studies on repeatability and strain limits.