Flexible wearable humidity sensor based on cerium oxide/graphitic carbon nitride nanocomposite self-powered by motion-driven alternator and its application for human physiological detection

Abstract

This paper presents a flexible wearable humidity sensor based on a cerium oxide/graphitic carbon nitride (CeO₂/g-C₃N₄) nanocomposite, which is self-powered by a motion-driven alternator. The self-powered CeO₂/g-C₃N₄ sensor demonstrated multifunctional application for human respiratory and skin dryness monitoring, indicating that it is a great prospect in the field of flexible and wearable electronics. The composition, morphology and structure of the CeO₂/g-C₃N₄ compounds are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The output electrical properties of the motion-driven alternator are investigated by rotating speed and external load. The energy acquisition circuit based on electromagnetic generator is designed. The capacitance of the CeO₂/g-C₃N₄ sensor is highly sensitive to changes in humidity. The humidity-capacitance measurement and display system is designed to be portable and compatible with a mobile smart phone and wireless communication technologies. Compared to pristine g-C₃N₄ or CeO₂ materials, the CeO₂/g-C₃N₄ sensor has a wider monitoring range as well as a faster and reversible response to humidity sensing at room temperature. The response value of the sensor reaches 6573 when the relative humidity (RH) increases from 0% to 97%. Compared with traditional humidity sensors, the CeO₂/g-C₃N₄ nanocomposite sensor has obvious advantages in terms of sensitivity (959.5 pF/% RH), responsiveness, stability, and recovery time. It can be applied to the detection of human physiological information.