A portable papertronic sensing system for rapid, high-throughput, and visual screening of bacterial electrogenicity

Electrogenic bacteria or exoelectrogens can transfer electrons to extracellular electron acceptors and thus have a wide range of applications to the ever-emerging fields of bioenergy, bioremediation, and biosensing. Standard state-of-the-art techniques for screening of electrogenic bacteria are inefficient, and often prevent rapid, high-throughput analyses. Herein, we created a simple, rapid, and straightforward papertronic 4- and 16-channel sensing platforms that is connected to a visual readout, allowing the naked eye to evaluate and quantify direct bacterial electrogenic capabilities. Our system integrated multiple 2-electrode sensing units into a signal amplifier circuit connected to light-emitting diode (LED) reporting units. The current generated from electrogenic bacteria in the sensing unit was amplified by the transistor and was transduced into LED illumination. The sensing units incorporated on the paper-based printed circuit boards (PCBs) absorbed bacteria-laden suspensions through capillary action, allowing for a rapid assessment (<2 min) of their electrogenic potential. Two well-known exoelectrogens, Shewanella oneidensis MR1 and Pseudomonas aeruginosa PA01, and many other mutants of the latter were selected to demonstrate the practicality of the proposed sensor. The effectiveness for on-site and portable measurements was validated by testing solid wastewater samples randomly obtained from the environment. Thus, the system described in this work highlights a novel form of a scalable, high-throughput sensing array for simple and rapid quantification of bacterial electrogenicity.