Electrospun nanofiber-based humidity sensors: materials, devices, and emerging applications

Humidity sensors, serving as essential electronic components for monitoring humidity levels, show widespread applications in environmental and human body related humidity detection. The development of nanomaterials has provided numerous opportunities in many fields, including humidity sensors. Electrospinning, as a simple technique for fabricating nanofibers, has garnered increasing attention in the field of electronics. Among them, electrospun nanofibers have shown promising prospects in high-performance humidity sensors due to their large specific surface area and high porosity. After years of development, although significant achievements have been made in electrospun nanofiber-based humidity (ENH) sensors, many challenges still exist in this field. This review article aims to systematically discuss the latest developments in ENH sensors. Firstly, we provide a comprehensive overview of the fundamentals of the electrospinning technique and humidity sensors. Secondly, the research progress of ENH sensors based on different materials (polymer nanofibers, oxide nanofibers, and composite nanofibers) and device types/working mechanisms (resistance, capacitance, impedance, frequency, and voltage/power generation) is reviewed and discussed. Thirdly, the emerging applications of ENH sensors in human body related humidity detection are discussed. Finally, the challenges and future development trends of ENH sensors are analyzed from different aspects. We hope that this review will offer valuable insights and guidance for future research on ENH sensors.