Sequential reinforcement of intra/interlayer interfaces to design flexible, transparent electromagnetic interference shielding film for “Green Electronics”

Biomass-derived composite films with flexibility, transparence and electromagnetic interference shielding properties are desired for “green” electronics. However, it remains challenging to achieve good compatibility of mechanical, optical, and shielding properties for the films due to weak interface bonding and high contact resistance within/between layers. Here, we propose a sequential reinforcement strategy to address the above issues by enhancing the intra/inter-layer interface bonding of multilayer films. A transparent and flexible cellulose nanofiber/nanoclay (CN) green substrate is first prepared by ion-assisted strengthening the intra-layer bonding of a brick-and-mortar structure. Subsequently, a robust MXene/AgNWs/MXene sandwich network (MAM) with significantly improved intra-layer electron transport and good transparency is constructed, benefitting from the ultra-strong capillary compression generated by the welding of upper and lower MXene layers. Meanwhile, the dual MXene layers can synchronously bridge the substrates through hydrogen bonds, ensuring strong inter-layer bonding. The obtained CN/MAM/CN composite film combines flexibility, high strength (>330 MPa), transparent (>50% transmittance) and high EMI shielding performance (>40 dB, in X band). Moreover, this film can withstand repeated mechanical deformations, low/high temperature thermal shock, and has gas barrier and flame retardancy abilities, which also broadens the application environment and improves the application safety.