Highly compressible lamellar graphene/cellulose/sodium alginate aerogel via bidirectional freeze-drying for flexible pressure sensor.

Graphene exhibits exceptional electrical properties, and aerogels made from it demonstrate high sensitivity when used in sensors. However, traditional graphene aerogels have poor biocompatibility and sustainability, posing potential environmental and health risks. Moreover, the stacking of their internal structures results in low compressive strength and fatigue resistance, which limits their further applications. In this study, green and sustainable cellulose nanofibers/sodium alginate/reduced graphene oxide aerogels (BCSRA) were synthesized, featuring a well-defined lamellar structure and a fiber cross-linked network, employing techniques such as bidirectional freeze-drying, ionic cross-linking, and thermal annealing. The unique internal architecture of BCSRA results in a compressive strength of up to 64.55 kPa at 70 % compression deformation and an extremely low density of merely 7.21 mg/cm. Furthermore, BCSRA displays outstanding fatigue resistance, maintaining 82.17 % of its stress after 100 compression cycles at 70 % compressive strain and 86.99 % after 1000 cycles at 50 % compressive strain. Remarkably, when utilized as a flexible pressure sensor, BCSRA achieves a sensitivity of 5.71 kPa and endures over 2200 cycles at 40 % compression, all while ensuring consistent electrical signal output. These properties underscore its significant potential for application in wearable flexible pressure sensors, capable of detecting various human movements.