Recently, the research article Reusable Self-Powered Electrochromic Sensor Patch Based on Enzymatic Biofuel Cells for On-Site Visualized Monitoring of Lactic Acid was published in Analytical Chemistry. Jiangsu University (JSU) is the first completed institution. Assoc. Prof. Wei Jie and Prof. Wang Kun are the corresponding authors.

Wearable sensors have broad application potential in motion assessment, health monitoring and medical diagnosis. However, most of reported wearable sensors still rely on complex non-mobile devices such as electrochemical workstations for power supply, signal conversion and reading. And these sensors can only convert perceptual information into electrical signal, lacking intuitive visualization functions.

To solve the above problems, in this work, lactic acid (LA) in sweat was used as the model analyte, and an electrochromic sensor patch based on enzymatic biofuel cells was constructed for visual monitoring. During the detection process, hydrophilic agar-hydrogel and hydrophobic SiO₂ film were used to control the collection and elimination of sweat. Lactate oxidase modified on the electrode was used to oxidize LA to pyruvic acid, achieving the conversion of chemical energy to electrical energy. The generated electrons transferred from the external circuit to the cathode, further reduced the Prussian blue (PB, colored state) modified on the cathode surface to Prussian white (PW, faded state). It could achieve semi-quantitative detection by reading color changes with the naked eye, or quantitative detection by output RGB values from smartphone apps. In order to reduce costs, PW was oxidized to PB by applying an external voltage after each detection, and the electrode changed from faded state to original blue colored state again, achieving the reuse of sensor patch. This work provided a new method for monitoring sweat LA and a new strategy for the formation of a general visualized wearable sensors.