An ultrafast QCM humidity sensor for respiratory monitoring outside a mask

In this paper, we developed a QCM humidity sensor based on TiO2/Ag composite nanowires. Appropriate amount of Ag nanowires can obviously promote the performances of QCM humidity sensor based on TiO2 nanowires. Apart from high response, the obtained QCM sensor also has ultrashort reaction time (0.4 /0.2 s), which surpasses most QCM humidity sensors. According to DFT calculations, this may be related with the reduction in Gibbs free energy of TiO2 nanowires due to the introduction of Ag nanowires. The sensor with high performances could be used for respiratory monitoring of infectious patients from the outside of a mask so as to reduce respiratory droplets infection to health-care workers, monitoring equipment and medical environment.