Self-powered, flexible and remote-controlled breath monitor based on TiO2 nanowire networks

Smart breath monitor devices with high stretchability, fast response/recovery times and self-powered characteristic are essential in the wearable medical and life science applications. In this work, we report on the development of a versatile high-performance humidity sensor based on TiO₂ nanowire networks for self-powered sensing application of human breath monitoring. These sensors, with typical response times of ∼3.6 s and recovery times of ∼14 s, exhibit high sensitivity to water vapor and can yield an output voltage that is directly proportional to the humidity level of ambient environment. The structure of nanowire networks is highly flexible and maintains the output voltage even after 10 000 times bending. By combining this type of sensor with a commercial signal transmission and processing system, it shows the good basis for real-time/remote-controlled monitoring and analysis of human breath under a variety of respiratory conditions. Our results suggest a new class of humidity sensing for self-powered biomedical devices and open to new technologies in energy, electronics, and sensor applications.