Self-powered round-the-clock spectral sensing towards in-situ evaluation of fruit quality

This work demonstrates a round-the-clock self-powered flexible spectral sensing device(FSSD) enabling in-situ fruit quality monitoring by resolving orchard energy supply limitations through synergistic photovoltaic power and moist-electric generation. This system integrates flexible solar patch (FSP) and flexible moisture-electric generator (FMEG) for hybrid energy harvesting, ensuring continuous operation through the compensation of photovoltaic power by moist-electric generation. The FMEG fabricated using the LiCl concentration-gradient design strategy to construct an ionic hydrogel film in a sandwich configuration which delivers the short-circuit current (Isc) of 0.73 V and short-circuit current density of 67.89 mA cm −2 at 80 % relative humidity. The FSP demonstrates excellent linear current response to illumination intensity from 5 k to 30 k lux, with short-circuit current (Isc) increasing from 12.81 mA to 115.21 mA, while delivering a stabilized Voc of 1.75 V at 30 k lux. The FSSD, which integrates spectral sensors and low-power control chip via flexible electronics technology and is powered by the hybrid energy supply, enables in-situ collection and wireless transmission of spectral data. Furthermore, through embedded partial least squares regression (PLSR) and support vector machine (SVM) machine learning models, it can realize real-time and continuous prediction of fruit quality parameters and evaluation of their ripeness levels. This easily manufacturable, scalable, and cost-effective system integrates autonomous energy harvesting with quality monitoring to construct a closed-loop digital decision-making framework for preharvest monitoring and post-harvest grading, which enables precision harvesting, reduces post-harvest losses, and advances technologies for precision agriculture and agricultural product traceability.