Multifunctional Wearable Sensing Devices Based on Functionalized Graphene Films for Simultaneous Monitoring of Physiological Signals and Volatile Organic Compound Biomarkers

In this study, a multifunctional wearable sensing device based on two different graphene films is fabricated and can achieve the simultaneous detection of physiological signals and volatile organic compound (VOC) biomarkers without mutual signal interference. The wearable device was designed with two sensing components: on the upper layer of the device, four kinds of porphyrin-modified reduced graphene oxide (rGO) films were prepared and used for a sensor array that could sufficiently react with VOC vapors to achieve highly sensitive detection. A porous rGO film was designed on the underlayer of the device and used as a strain-sensing matrix, which could be closely attached to the skin to achieve a highly sensitive detection of the physiological signal. A polyimide film between the two sensing components was used not only as a flexible substrate, but also as a protective layer to avoid the porous rGO film's response to VOC molecules. Investigation of the detection ability showed that the porous rGO strain-sensing matrix can achieve a higher gauge factor (282.28) than the unstructured rGO counterpart (8.96) and is more desirable for the detection of physiological motion. In contrast, the porphyrin-modified rGO sensor array displayed a superior response to VOC vapors, and eight different VOC biomarkers could be detected and discriminated using the as-prepared sensor array together with a pattern recognition approach. The multifunctional sensing devices displayed excellent ability for the detection of a variety of human physiological signals, such as pulse and respiration rates. Simultaneous analysis of simulated diabetic breath samples, simulated nephrotic breath samples, and breath samples exhaled by healthy individuals using our wearable device exhibited clear identification and discrimination. Our study provides new insights into fabrication and design of multifunctional sensing devices without signal interference, and the application of the proposed devices are promising in preventive medicine and health care.