A Self-Powered Biosensor System: Integrating Upcycled MFC Transducers With Low-Voltage Interface Circuits

Abstract

autonomous, self-powered instrumentation systems is critical for distributed environmental Internet of Things (E-IoT) wastewater monitoring. This study presents a low-cost, self-powered measurement framework featuring a proton exchange membrane (PEM)-free, single-chamber microbial fuel cell (MFC) as a bioelectrochemical transducer. Utilizing a strain-independent" mixed-culture biofilm within an upcycled polyethylene terephthalate (PET) bottle structure the system converts organic analytes into electrical signals. A five-point calibration demonstrated a linear range of 50-250-mg/L chemical oxygen demand (COD) [R-2 = 0.98 sensitivity = 0.69 mV/(mg/L) limit of detection (LOD) = 35 mg/L]. Under continuous-flow operation a single transducer maintained a stable output of 0.14 V for 21 days [coefficient of variation (CV) = 2.8 %]. The MFC units exhibited a peak power density of 8.6 mW/m2 (interunit CV = 6.8 % n = 12) with a 12-unit array delivering approximately 51 & micro;W of regulated power. A dedicated sensor interface circuit converts the weak similar to 140-mV biosignal into a binary digital alarm output (0/3.3 V) with a total active consumption of only 9.78 & micro;W (interface circuit: 9.24 & micro;W; autonomous reference voltage generation: 0.54 & micro;W). The resulting positive energy margin of 41.22 & micro;W (5.2:1 surplus ratio) validates the thermodynamic feasibility of fully autonomous operation. This work demonstrates a complete "transducer-to-digital" pathway providing an experimentally verified foundation for battery-free water-quality early warning networks."