The rapid progress of advanced technologies relying on wireless telecommunications systems, such as 5G and 6G networks, the Internet of Things (IoT), and artificial intelligence (AI), has driven the demand for sustainable materials with dynamically adjustable properties. This study introduces composite films of cellulose nanofibers (CNF) and VO₂ nanoparticles with mixed and sandwiched hybrid structures. Leveraging the insulator-to-metal transition (IMT) of VO₂, these films exhibit reversible changes in GHz permittivity under thermal stimuli, enabling dynamic control of their electrical performance. 
The hybrid film with a mixed structure was demonstrated as a reconfigurable intelligent surface (RIS), enabling the manipulation of incident electromagnetic waves, making it suitable for 5G/6G wireless signal applications. Additionally, the sandwich-structured film serves as a switchable electromagnetic interference (EMI) shield, showing significant differences in shielding efficiency between its hot and cold states. This dual functionality underscores the potential of CNF/VO₂ composite films as versatile, adaptable platforms for intelligent electronics. By using deep eutectic solvent (DES) treated cationic cellulose, the transparency of substrate cellulose also leaves an opening for optoelectronic applications for the material.
By addressing the need for materials that can dynamically respond to external stimuli, this study gives insight on sustainability-focused material development in signal propagation control, EMI shielding, and optoelectronic applications. The use of cellulose nanofibers and simple manufacturing methods further emphasizes the environmental benefits, aligning with the growing demand for green electronics.