Glass Microfluidic Bioelectrochemical Cell Platform for the Study of Extracellular Electron Uptake in Microbes

Miniaturization of microfluidic measurement systems offers several advantages, including reduced sample and reagent volumes, improved control over experimental conditions, and the ability to multiplex complementary measurement modalities, to enable new experimental approaches in microbial electrochemistry. We present a scalable glass-based microfluidic bioelectrochemical cell (µ-BEC) platform for multiplexed investigations of microbial extracellular electron uptake (EEU). The platform integrates eight independently addressable three-electrode cells in a 2×4 array, with transparent indium tin oxide working electrodes that support simultaneous electrochemical analysis and optical imaging. Systematic electrochemical characterization using the ferri/ferrocyanide redox couple demonstrated diffusion-controlled behavior and stable reference electrode performance, with well-to-well coefficients of variation in peak potentials of 0.6–1.5% and 0.6–1.1% for anodic and cathodic processes and device-to-device coefficients of variation of approximately 1.8% and 1.6%, respectively. Differential pulse voltammetry measurements demonstrated concentration-dependent electrochemical sensing over a three-order-of-magnitude range from 1 µM to 1 mM ferri/ferrocyanide, with peak currents exhibiting linear dependence on concentration for both anodic and cathodic processes across all tested wells. Biological compatibility was validated using the phototrophic bacteria Rhodopseudomonas palustris TIE-1, where reproducible light-dependent EEU was observed following 96 hours of incubation, and a reduction in current response after microfluidic removal of planktonic cells confirmed the contribution of surface attached cells to EEU. Together, these results establish the µ-BEC as a robust and reproducible microfluidic electrochemical platform suitable for parallelized, multimodal studies of microbial and abiotic electrochemical processes.