Wood-Inspired Anisotropic Cellulose Nanofibril Composite Sponges for Multifunctional Applications

Nanocellulose-based porous materials have been recently considered as ideal candidates in various applications. However, challenges on performances remain owing to the disorderly structure and the limited transport specificity. Herein, wood-inspired composite sponges consisting of cellulose nanofibrils (CNFs) and high-aspect-ratio silver nanowires (AgNWs) were generated with anisotropic properties by the directional freeze-drying. The obtained composite sponges exhibited attractive features, such as an excellent compressive stress of 24.5 kPa, low percolation threshold of 0.1 vol % AgNWs, and high electrical conductivity of 1.52 S/cm. Furthermore, the self-assembled ordered structure in the longitudinal direction and synergistic effect between CNFs and AgNWs benefited the sponge interesting anisotropic electrical conductivity, thermal diffusivity, ultrafast electrically induced heating (<5 s), sensitive pressure sensing (errors <0.26%), and electromagnetic interference (EMI) shielding for special practical demands. This multifunctional material inspired by natural woods is expected to broaden new applications as electronic devices for an intelligent switch or EMI shielding.