3D-printed sodium alginate/carbon nanotube/graphene porous scaffolds crosslinked with Ca2+ for high-performance electromagnetic shielding and Joule heating

High-performance green functional materials have garnered significant interest for electromagnetic interference (EMI) shielding applications, but creating customized, low-density, high-strength and high-efficiency biomass-based shielding materials remains challenging. In this study, lightweight Ca²⁺ doped sodium alginate (SA) porous scaffolds with a carbon nanotube (CNT)/graphene (Gr) hybrid conductive network were fabricated via direct ink writing (DIW) 3D printing. The SA/CNT/Gr inks with unique rheological properties were formulated and architectures with arbitrarily customized structures could be freely constructed based on the printable inks. The incorporation of Ca²⁺ facilitated the construction of hierarchical crosslinking networks, which imparted the SA/CNT/Gr/Ca²⁺ porous scaffolds with improved compressive strength (a 136 % increase), excellent chemical stability (maintaining integrity in both acidic and alkaline environments for up to 30 days) and enhanced electrical conductivity (131.3 S/m). Benefiting from their porous structure and robust conductive network, the porous scaffolds achieved an admirable EMI shielding effectiveness (SE) of 54.8 dB and a high specific shielding effectiveness (SSE) of 322.35 dB·cm³·g⁻¹ in the X-band. Furthermore, the porous scaffolds also exhibited distinctive Joule heating performance, and their surface steady-state temperature reached 124.6 °C under a low applied voltage (≤ 3 V), indicating great potential for thermal management in integrated systems.