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/transmitting 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.