Advances in E-Plant Sensors: Material Design, Signal Transduction, and Self-Powered Intelligent Systems

Electronic plant (E-Plant) sensors are emerging as an important platform for next-generation smart farming because they can monitor plant growth, water status, microclimate, nutrient ions, metabolites, and stress responses in real time. By directly interfacing plants or their growth media, these sensors provide closer insight into plant physiological changes than conventional environmental monitoring systems. Therefore, E-Plant sensors must combine high sensitivity with mechanical flexibility, conformability, long-term stability, biocompatibility, and environmental sustainability without disturbing plant growth. This review summarizes recent advances in E-Plant sensors from the perspectives of material design and signal transduction. Representative examples include conductive-network-based mechanical and moisture sensors, semiconducting and surface-reactive sensors for environmental and stress monitoring, ion-conductive and electrochemical sensors for soil and metabolites, and flexible, low-interference plant-attached sensors. Self-powered wireless systems, multifunctional sensor arrays, and machine-learning-assisted diagnosis are also discussed. Finally, key challenges and future opportunities for intelligent farming systems are outlined.