Anti-interference monitoring of sweat pH: a new sensing mechanism based on the p–n transition potential of a flexible Bi2O3 photoelectrode

Abstract

The anti-interference capability is vital for flexible wearable sensors, especially for detection during exercise. Herein, we propose a new sensing strategy based on the p–n transition potential (V_p–n) of the Bi₂O₃ photoelectrode. The V_p–n decreases linearly with pH and more importantly it demonstrates strong anti-interference performance against the change in the coverage of sweat on the photoelectrode, the variation in light intensity, and the bend of the photoelectrode. Moreover, the Bi₂O₃ photoelectrode shows good flexibility and biocompatibility, based on which a pH monitor that can interact with a smartphone is developed, enabling convenient and accurate monitoring of sweat pH during practical exercise. The monitor exhibits a benchmark signal-to-noise ratio that is one order of magnitude higher than that of the state of the art pH monitors. The strategy of using the V_p–n signal of a semiconductor for pH sensing is proposed for the first time, which opens a new avenue for designing anti-interference wearable sensors.