| 초록 |
Wearable devices have attracted attention as a technology that detects human body signals in real-time. Among various biosignals, sensing of respiration and body temperature, which are important physiological signals of humans, is essential. To measure the biosignals directly and quickly, research on wearable and attachable sensors is necessary. Herein, we report humidity and temperature sensors based on a graphene oxide material, whose electrical characteristics are tailored by controlling the degree of reduction depending on the exposure time to hydroiodic acid (HI) vapor. The microstructure and chemical state of the graphene oxide materials, as well as their optical and electrical properties, demonstrate their suitability as temperature and humidity sensors. Especially, through XPS/FT-IR analysis, the epoxy functional group is a decisive role in the sensitivity of the humidity sensor as a water molecule adsorption site, and it can explain the sensitivity of the temperature sensor according to the defect states related to the degree of reduction by photoluminescence spectroscopy (PL) analysis results. The graphene-oxide-based humidity sensor exhibits a superior sensitivity (2.71 %∙%RH-1) and good response and recovery properties compared to the commercial sensor. It is confirmed that respiration and apnea can be detected and distinguished separately. On the other hand, the partially reduced graphene-based temperature sensor showed high performance, in particular, high sensitivity (0.964 %∙˚C-1), excellent linearity (R2 = 0.999), and good repeatability. The direct/indirect measurement of body temperature, water droplet, and touch test are conducted. Finally, a mask-type wearable device based on a wireless platform is implemented through coating onto flexible substrates, confirming that the real-time monitoring related human health, such as respiration, is possible. The fabricated sensor has various potential applications related to realistic scenarios within our daily lives. |
