Self-powered wearable plant chlorophyll sensing patch

Monitoring the chlorophyll content of plants can assess crop growth, guide precise fertilization, predict crop yield, etc., which is of great significance for realizing smart agriculture. However, current chlorophyll measurement methods cannot realize this goal. A fast, non-destructive and long-term self-powered chlorophyll monitoring system is proposed. The overall system consists of a miniaturized plant chlorophyll sensing patch (PCSP) and the photovoltaics (PV) -Tribovoltaic nanogenerator for wind energy harvesting (WTVNG)-soil microbial fuel cell (SMFC) triple energy system (PWSS). The PCSP utilizes a reflective optical mode, has a thickness of 4.8 mm and a weight of 2.6 g. It includes a light-emitting diode (LED) and four symmetrical photodetectors (PDs) on a flexible substrate. The whole is wrapped with a light-guiding layer (LGL). The chlorophyll content index (CCI) calculated based on PCSP had a good linear relationship (r² > 0.9) with chlorophyll content. PWSS is self-powered by using solar energy as the core power supply and making full use of wind energy in the environment and chemical energy in the soil. The short-circuit current density of the WTVNG at 180 rpm is approximately 7.21A/m². The power density of the SMFC is 1.18 mW/m³. Combining the measured chlorophyll content with the LSTM algorithm can be used to categorize stress and predict the chlorophyll content of plants under continuous stress. The overall system is suitable for long-term unmanned monitoring of plants, and detects the stress condition of plants earlier than the traditional chlorophyll meter and visual observation, which have promising applications in smart agriculture.