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Organic electrochemical transistors (OECTs) are thin-film devices operated in aqueous and biological environments for sensing chemicals and biomolecules. However, most sensor configurations involve introducing the target biomolecule directly in the OECT device. This has drawbacks because it may not be possible to have an electrolyte compatible with the target biomolecule or an environment optimal for the OECT. Here, we demonstrate a general and modular approach to building electrochemical sensors by coupling OECTs electronically with either an enzymatic fuel cell (EFC) or microbial fuel cell (MFC). We demonstrate that this modular approach can amplify currents by three orders of magnitude and enhance the signal-to-noise ratio. We also show that the power generated by the fuel cell can help tune the sensor’s response for different applications. This work demonstrates a simple and versatile approach for amplifying currents from MFCs and EFCs useful for the development of bioelectronic sensors. 

In a world confronting pollution across diverse environments, fast, sensitive and cost-efficient methods are required to monitor complex chemicals. In particular, microbial bioelectronic sensors can report on the presence of chemicals through electrical signals enabled by biological processes. For example, microbial bioelectronic sensors have been developed for the rapid detection of riverine toxins within minutes of contact, for selective sensing of redox-active pharmaceuticals, and for monitoring of pesticide degradation. However, transferring these laboratory-tested technologies into field-deployable products poses several challenges: sensor sensitivity, specificity, longevity and robustness need to be improved. In this Review, we discuss the design of field-deployable microbial bioelectronic sensors, including chassis selection, approaches for rewiring electron transfer, strategies to establish the cell–electrode interface and fabrication methods. Importantly, we outline key challenges and possible solutions for the application of such sensors in the real world.