A battery-free music-driven humidity sensor for intelligent wearable sensing system in smart diaper

A potential intelligent multifunctional diaper with the integration of flexible sensors and data processing ransmitting units may have the functions of monitoring the urination of babies, detecting the physiological parameters and transmitting the information to the mobile terminal of their parents. Here, we present a battery-free music-driven humidity sensor for an intelligent wearable sensing system in a smart diaper. The working mechanism is based on the coupling of the triboelectric effect and the humidity-sensing process. Driven by baby-acceptable musical sound, the two layers of the device vibrate (resonance effect), and the triboelectric effect generates an electrical output. The output decreases with the increasing humidity, acting as both a power source and humidity-sensing signal. The sensor can be embedded in a diaper to monitor the urination of the baby, and a wireless transmitter is integrated in the system to upload the information. The present results can promote the development of the next generation of self-powered active sensors and expand the scope of battery-free sensing systems.