All‐Biomass Nanocomposite Films via Facile and Sustainable Design Procedure for Thermal Management and Electromagnetic Interference Shielding

Abstract Emphasizing sustainability and low‐cost flexible films to overcome thermal accumulation and electromagnetic radiation pollution is an urgent need in response to the lightweight and integrated development of electronic devices. Herein, a fully biomass‐derived nanocomposite film is proposed and fabricated by self‐assembling nano carbon spheres (NCSs) and cellulose nanofibers (CNFs) through a simple and scalable vacuum‐assisted filtration method. The results reveal that the development of ordered and graphitized structures of NCSs through high‐temperature pyrolysis facilitates π–π stacking, interfacial adhesion, and the construction ofconductive networks in the NCSs/CNFs films (NCF). Among all the NCF samples, NCF 5:5 achieves a tensile strength of 41.74 MPa, in‐plane thermal conductivity of 2.21 W·m −1 ·K −1 , and EMI shielding of 23.77 dB, representing the most balanced integration of mechanical, thermal, and shielding properties. Simultaneously, it maintains infrared stealth and stable performance over 100 deformation cycles. The synergy of all‐biomass composition, green fabrication, and superior multifunctional properties highlights the potential of the NCF in flexible electronics, wearable devices, and eco‐friendly EMI shielding applications.