Bioderived Cellulose Aerogel Fibers with Hierarchical Porosity for Millisecond Hydrovoltaic Sensing.

Real-time moisture sensing is crucial for environmental monitoring and food safety. However, conventional humidity sensors relying on moisture-induced changes in conductivity or capacitance are often constrained by sluggish water adsorption-desorption kinetics and inefficient ion transport through disordered nanochannels. Here, we develop cellulose aerogel fibers derived from natural rattan, featuring hierarchical and interconnected porosity, to enable ultrafast hydrovoltaic moisture sensing. The tailored pore network expedites the diffusion of trace moisture and substantially amplifies the solid-liquid interfacial area within the fiber, thereby boosting the formation of electric double layers and enhancing water-ion coupling. Consequently, the self-powered sensor delivers a detectable voltage response within 70 ms upon exposure to only 10 μl of water microdroplets, achieving both rapid detection and high sensitivity. Moreover, the device exhibits versatile responsiveness to multiple environmental parameters, and its sensing behavior can be readily tuned by manipulating the fiber configuration (linear, helical, and branched). All 3 configurations achieve a fast response to approximately 0.1 V within 70 to 310 ms, followed by a voltage increase to 0.49 to 0.63 V within 3 to 5 s. This work highlights the critical role of porosity engineering in cellulose aerogel fibers and provides a new strategy for developing high-performance biomass-based hydrovoltaic sensing systems.