A Gradient‐Structured Nanofiber Sensor Integrating Moisture‐Induced Voltage Generation and Resistive Humidity Sensing for Plant Transpiration Monitoring

Recently, plant species decline, reduced crop productivity, and declining efficacy of Chinese herbs have raised growing concern, largely due to environmental change and biotic stress. Intelligent plant health monitoring systems enabling early detection and dynamic tracking are therefore essential. Although flexible wearable sensors offer good biocompatibility, the requirement for external power remains an important challenge for long‐term field deployment. Here, we developed a plant‐transpiration‐responsive sensor based on gradient‐structured cellulose acetate (CA) nanofiber membranes and MXene nanosheets. An asymmetric gradient was constructed by tuning the doping ratio of poly(4‐styrenesulfonic acid) (PSSA) through electrospinning, enabling moisture‐induced voltage generation under a humidity gradient. This structure promotes directional moisture transport and ionic migration, allowing a single device (1.5 × 1.5 cm 2 ) to produce an open‐circuit voltage of ∼1187 mV at 75% relative humidity (RH). Owing to the high conductivity and humidity sensitivity of MXene, the same device integrates moisture‐induced voltage generation with resistive humidity sensing for real‐time transpiration monitoring. This study offers a sustainable, non‐invasive strategy for plant health monitoring and early stress warning and supports the integration of smart agriculture and green energy.