Additive manufacturing of multifunctional <scp>PEEK</scp>‐carbon fiber‐<scp>CNT</scp> lattices composites for tunable temperature and force sensing

Abstract This study details the exploration of a novel PolyEtherEtherKetone (PEEK) ‐ Carbon Fiber (CF)/Carbon Nanotubes (CNT) filament designed for additive manufacturing of lattice structures with controlled thermo‐piezoresistive properties. PEEK, a semi‐crystalline thermoplastic material with excellent strength and thermal stability, exhibits enhanced electrical conductivity when paired with CNTs. The combined presence of CNT and CF allows for improved structural integrity and reliable signal responsiveness, making the PEEK‐CF/CNT composite ideal to use in additive manufacturing of high‐performance sensors. Moreover, the printing of structures with stress plateau regions such as Auxetic 3D and Truncated Octahedron lattices enables controlled temperature or force sensing. Plateau stress present at 5%–15% strain allows for the decoupling of piezoresistive and thermoresistive responses within the lattice structures with a 99.7% repeatability up to 100°C. This mechanism is crucial for applications requiring differentiated responses to mechanical and thermal stimuli, allowing the composite to selectively respond to changes in force or temperature without interference from the other variable, essential for accurate and reliable sensing in complex environments. This advancement in using PEEK‐CF/CNT composites marks a significant contribution to additive manufacturing of multifunctional composites with embedded sensing. Highlights Developed PEEK‐CF‐CNT filament for FFF additive manufacturing. Identified optimal CNT content for enhanced conductivity and strength. Tuned lattice structures for selective force and temperature sensing. Achieved 99.7% repeatability in thermo‐piezoresistive response. Enabled decoupling of mechanical and thermal sensing in lattices.