Layer-by-layer assembly of boron arsenide and copper nanoflake-based aramid nanofibers for thermoconductive electromagnetic interference shielding materials with superior mechanical flexibility and flame retardancy

Flexible and wearable electronics represent an emerging frontier, but realizing their potential requires addressing challenges like electromagnetic interference (EMI) shielding, electrical insulating thermal management, and mechanical flexibility. Layer-by-layer structure with alternating conductive and insulating layers offers a promising solution. In this work, we fabricated layer-by-layer structured papers combining boron arsenide (BA) as insulating layers and two-dimensional copper nanoflake (CuF) as conductive layers based on aramid nanofiber (ANF) film via alternating vacuum filtration. The resultant paper (BA4/CuF3) consists of 3 layers of CuF (50 wt%) based ANF (CuF@ANF) conductive layers sandwiched between 4 layers of BA (50 wt%) based ANF (BA/ANF) insulating layers providing exceptional EMI shielding effectiveness (SE) up to 52 dB in the X-band frequency, and in-plane thermal conductivity up to 32.8 W/mK. Meanwhile, the composite papers also demonstrate excellent mechanical flexibility, with the BA4/CuF3 papers exhibiting a tensile strength of 92.38 MPa and EMI SE above 50 dB. Moreover, the composites impart thermal stability up to 500 °C and reduce flammability. The concurrent enhancement of EMI shielding, thermal conductivity, and mechanical properties confirms the potential of layer-by-layer BA/CuF papers for next-generation flexible electronics demanding electromagnetic protection and thermal management.