Anisotropic carbon aerogels with XYZ three-direction superelasticity for piezoresistive sensing applications

It is still a challenge to construct XYZ three-direction elastic carbon aerogels with high fatigue resistance and compressive strength based on biomass materials. In this work, directional freezing technology combined with bubble template method was used to construct three-direction compressive elastic carbon aerogles with a unique “tube-bubble” structure using rigid bacterial cellulose (BC) as skeleton and flexible sodium alginate (SA) as adhesive. The honey-comb tube structure derived from direction freezing significantly enhanced the mechanical strength of aerogel and generated transverse direction (x,y) elasticity. The presence of bubble cavity further endowed the aerogel with compressive elasticity in all XYZ directions, especially solving the limitation of longitudinal (z-direction) elasticity. Under 70 % strain, the plastic deformation of carbon aerogel was still less than 0.24 % after 1,000 compression cycles in all three directions. In addition, the pressure sensor assembled based on carbon aerogel exhibited a wide pressure range of 0–5.1 kPa in three directions, a low detection limit of 3 % strain, and a high sensitivity more than 17.8 kPa⁻¹. The biomass-based carbon aerogel with three-direction superelasticity and excellent conductivity is capable of detecting complex human joint movements, wind disturbance and low-frequency multidirection vibrations.