Hybrid silver nanoparticle–boron nitride fillers enabling high thermal conductivity in 3D-printed PDMS composites

Thermal management remains a major challenge for miniaturized and flexible electronics, where polymer composites often trade thermal conductivity for compliance and processability. Here, we present 3D-printable thermal management materials (TMMs) based on polydimethylsiloxane (PDMS) incorporating hybrid silver nanoparticle–boron nitride (AgNP–BN) fillers. Two AgNP decoration strategies were compared: a conventional route using N,N-dimethylformamide (DMF) and a greener isopropanol/water co-solvent with trisodium citrate as reducing agent. Structural analyses revealed that the DMF process induced secondary AgCN phases, whereas the citrate route yielded AgNP deposition without byproducts. Hybrid fillers were formulated into shear-thinning inks suitable for direct ink writing (DIW), which enabled anisotropic filler alignment during printing. The composites achieved thermal conductivities up to 1.40 W m⁻ 1 K⁻ 1 , representing a nearly 9-fold enhancement over neat PDMS and a 79 % improvement compared to BN-only systems, without increased filler loading. This work demonstrates the synergistic benefits of filler hybridization and extrusion-based additive manufacturing, establishing a sustainable pathway for lightweight, flexible, and high-performance TMMs for wearable devices, conformal electronics, and advanced packaging.