A Portable and Visual Electrobiochemical Sensor for Lactate Monitoring in Sweat

We report a novel paper-based sensing strategy based on microbial electrochemical activities, in which a reusable voltage meter integrated with a read-out LED display monitors a self-powered transducing signal from a disposable paper-based sensing strip for lactate monitoring in sweat. This sensor strip self-produced an electrochemical potential difference when electricity-producing bacterial cells (or exoelectrogens) oxidized the biodegradable organic substrate, lactate, and transferred electrons to an electrode. Because the harvested electrons were based on their electrochemical energy conversion and were proportional to the lactate concentration, the voltage output through an external resistor could be used as a transducing signal for lactate monitoring in sweat. The output signal was easily readable with an inexpensive digital multimeter, which could be repeatedly connected to the disposable sensing strip. The LED display showed a linear range of output voltage at 0.0 40.0 mM lactate concentration (R2 =0.977) with a 1001:51 resistor. Thus, our new sensing system holds great promise in designing portable and low-cost sensors for point-of-care and daily applications.