## 1 Introduction
This sensor had two components: a structural part made of a TPU filament and a sensing part made of a TPU/MWCNT nanocomposite filament with surface piezo-resistivity. These parts were produced simultaneously using 3D printing. This method allowed customization and quick production and was cost-effective, allowing for the direct fabrication of multiaxial sensors without additional assembly or integration. PCMs are widely employed for various applications, especially for enhancing the thermal comfort of buildings, in solar heating systems, in thermal protection systems, air-conditioning, transportation, electronic devices, thermal regulated textiles, etc. Nowadays, PCMs are integrated into fabrics and clothes to regulate skin temperature, thereby increasing thermal comfort and/or alleviating heat strain [26; 27; 28; 29]. These materials can absorb excess body heat generated during physical activity and release it when needed, thus maintaining a stable temperature for the wearer. For instance, PCM-treated active wear is designed to balance the heat produced by the body with the heat released into the environment, which is crucial to prevent thermal stress during intense sports activities [27; 28]. Specific applications include gloves for ice climbing and cycling, wherein PCM's ability to regulate temperature can improve comfort and performance. The incorporation of PCMs into sports textiles not only enhances thermal regulation but also contributes to the overall functionality and comfort of the garments used in various athletic activities [30]. Additionally, mathematical modeling indicated that wearing a PCM cooling vest could substantially decrease body heat load, highlighting the vest's role in enhancing thermal comfort [31]. Furthermore, the effectiveness of PCMs in reducing thermal strain has been corroborated by various studies, which noted that the cooling effect is influenced by factors such as vest design and environmental conditions [32; 33]. In the last few years, our research group focused its attention on the development of multifunctional 3D-printable TPU-based materials with thermal energy storage (TES)capability thanks to the addition of microcapsules filled with paraffin [34; 35]. The encapsulation of Phase-Change Materials (PCMs), able to absorb/release thermal energy as latent heat upon a phase change, has opened a new route for fabricating smart materials with improved multifunctionality [36]. In the previous work performed by our group, we highlighted the possibility of successfully printing TPU blends with 40 wt% PCM through FFF technology, yielding multifunctional materials with good thermal energy storage efficiency and suitable mechanical properties [37]. In this sense, the addition of a conductive nanofiller within the TPU matrix could enhance the thermal and electrical conductivity of the resulting materials, giving rise to novel 3D-printed multifunctional structures that could be applied in smart electronics and sensors or in sport applications. This study introduces, for the first time, the development of 3D-printed TPU/MWCNT nanocomposite materials incorporating PCM for thermal management applications. Utilizing the FFF process, the integration of PCM and CNTs into TPU enhances the material's thermal properties. The 3D-printed samples, with varying quantities of PCM and MWCNTs, were thoroughly characterized to evaluate their morphological, thermal, and mechanical properties, marking a significant advancement in the field of thermal management.