Negative Poisson's Ratio in Cellulose Nanocrystal Aerogels for Enhanced Sports Piezoelectric Sensing

Abstract Cellulose nanocrystal (CNC)‐based aerogels hold promise as materials for piezoelectric sensors, given their biodegradability, cost‐effectiveness, and adaptable mechanical properties. However, cellulose‐based mechanoelectrical sensors often suffer from limited performance due to poor sensitivity and output, arising from inadequate stress transfer and mechanoelectrical coupling. In this study, a novel metastructure with a negative Poisson's ratio (NPR) is introduced to boost the piezoelectric performance of cellulose‐based aerogel sensors. To activate crystal‐based piezoelectricity and maintain the aerogel's flexibility, CNC crosslinked with flexible polyethylene glycol (PEG) is utilized. A biaxial compression method is employed to create anisotropic NPR structures, which achieve self‐polarization of this piezoelectric device. The results show that the NPR structure, which presents asymmetric auxetic properties, amplifies the piezoelectric output voltage by 25.7‐fold. Moreover, the piezoelectric output voltage density and the piezoelectric constant reach impressive values of and 5.33 pC , respectively. The NPR aerogel‐based piezoelectric device, with a series‐parallel connection, exhibits high output stability and has potential applications in monitoring various human sports activities.