Morphology-dependent electrical response of CO2-foamed conductive TPU filaments fabricated by foam additive manufacturing

The integration of lightweight, conductive, and mechanically compliant materials is essential for the development of next-generation wearable and flexible electronic systems. Conductive foamed polymers, in particular, offer a promising route to combine low density with tailored electrical functionality, yet process control remains challenging. This work demonstrates a practical and scalable route to fabricate electrically conductive thermoplastic polyurethane (TPU) foams by Foam Additive Manufacturing (FAM) which combines the process of CO2 absorption with fused-filament foam printing (FFF). The present study systematically explores how processing parameters govern filament expansion, cell structure, and porosity, and how these morphological features influence electrical and mechanical behavior. The approach yields well-defined microcellular architectures with morphology-driven modulation of electrical conductivity, while preserving ohmic response across all conditions. Normalizing the resistivity enables the demonstration of a direct correlation between the foam structural features and charge transport behavior. This approach offers a reproducible framework for tailoring conductive performance through a controlled foaming process. The resulting filaments demonstrate a balanced combination of elasticity and electrical functionality, offering interesting perspectives for the development of wearable smart devices.