With ecological environment deterioration, water pollution, energy crisis and global warming, renewable energy sources have become crucial for frontier environmental protection and energy alternatives. Bio-electrochemical system (BES) as a dynamic system enables to in situ convert organic contaminants in wastewater to electricity through the metabolism of electroactive microorganisms. However, a complete picture of physiochemical and electrochemical reactions is still unlocked in the “black box” of BES systems. Traditional water quality analytical methods (e.g., colorimetric, chromatographic, biometric, and electrochemical sensors) are usually performed in passive monitoring modes, requiring samples to be taken to specific instrument for analyses, which are complicated, tedious, time-delayed, and energy consumption. To attain longterm “maintenance-free” monitoring in BES systems, uninterrupted sensor reading transmission could be a solution. Nevertheless, frequent data transmission (e.g., once per second, once per minute) requires external energy source, which could incur uncertainty under power outage condition. To address this long-standing challenge, an integrated power entity consisting of a miniature microbial fuel cell and a triggered power management system was developed to power the potentiometric millimeter-sized solid-state membrane (S-ISM) water sensors (e.g., ammonium, nitrate, lead, etc.) for real-time in situ monitoring and uninterrupted transmission of sensor readings under diverse contaminant shocks in wastewater. In this study, the potentiometric sensors’ real-time and long-tern continuous monitoring capability are enormously enhanced by modifying their ion selective membrane materials (e.g., PTFE-loaded membrane) and solid contact layer materials (e.g., PEDOT layer), and membrane deposition approach. This “maintenance-free” monitoring will decode wastewater characteristics under various operational parameters, and thus greatly enhance the understanding of complex microbials structure and considerable metabolism reactions occurring in BES systems. In addition, accurate and continuous monitoring of soil nitrogen is also critical for determining its fate and providing early warning for swift soil nutrient management. However, the accuracy of existing electrochemical sensors is hurdled by the immobility of targeted ions, ion adsorption to soil particles, and sensor reading noise and drifting over time. Thus, the novel S-ISM water sensors were expanded into the soil environment by coating a hydrogel layer onto the surface of S-ISM to absorb water contained in soil and, consequently, enhance the accuracy and stability of these sensors monitoring nitrogen in soil. This pioneering study establishes a framework capable of real-time in situ, long-term continuous soil monitoring, a crucial technology with profound impacts on soil system resilience, nutrient management, contaminant removal, and energy-saving practices.
