Wood-inspired elastic and conductive cellulose aerogel with anisotropic tubular and multilayered structure for wearable pressure sensors and supercapacitors.

Cellulose nanofiber (CNF) aerogels hold considerable potential in wearable devices as pressure sensors and flexible electrochemical energy storage. However, the undirectional assembly of CNFs results in poor mechanical performance, which limits their application in structural engineering. In this study, we propose an anisotropic aerogel with both elastic and conductive properties inspired by the micro-nanostructure of natural wood. One-dimensional TEMPO cellulose nanofibers (TOCNF) were utilized as structural building blocks, while two-dimensional reduced graphene oxide (rGO) served as the electron transfer platform, owing to their high mechanical strength. The directionally aligned tubular structure composed of multilayered sheets was formed through rapid unidirectional freezing and subsequent steam heating reduction. These structures efficiently transferred stress throughout the porous skeleton, resulting in TOCNF-rGO aerogels with high compressibility and excellent fatigue resistance (2000 cycles at 60 % strain). The aerogel also exhibited high sensitivity, wide detection range, relatively fast response, and excellent compression cycle stability, making it suitable for accurately detecting various human biological and motion signals. Additionally, TOCNF-rGO can be assembled into a flexible all-solid-state symmetric supercapacitor that delivers excellent electrochemical performance. It is expected that this biomass-derived aerogel will be a versatile material for flexible electronic devices for energy conversion and storage.