Simultaneous detection of ultraviolet irradiation and vitamin C using an all-carbon-based integrated wearable system...

Ultraviolet (UV) radiation is a harmful exogenous factor for human skin. Wearable UV photodetectors can monitor UV exposure in the surroundings, and wearable vitamin C (V_C) sensors tracking the levels in the human body present the potential ability to defend the UV radiation. Herein, we reported on the fabrication of an all-in-one wearable system with a UV photodetector and V_C sensor powered by a micro-supercapacitor. Based on direct laser writing carbonization of polyimide sheets, the patterned electrodes and interconnects of the circuit were fabricated by a facile one-step operation, obtaining an all-carbon-based integrated system. Such a system exhibited outstanding energy storage ability (56.2 μWh cm^-2 at 4.17 mW cm^-2), high areal capacitance (1.06 mF cm^-2 at 5 mV s^-1), satisfying capacitive stability, and good mechanical flexibility. The UV photodetector and the V_C sensor were powered to obtain a linear range of UV intensity from 11 to 44 μW cm^-2 (equivalent to Ultraviolet Index 4.4 to 17.6), and V_C levels of 1.0-200 μM with a low limit of detection of 0.83 μM. Furthermore, the integrated system was successfully applied to the determination of V_C in commercial beverage and human sweat samples. This work provided a simple and promising method to fabricate integrated wearable systems for on-site providing information on the UV intensity of the external environment and the V_C level of the human body simultaneously.