A CNFs/MWCNTs aerogel film-based humidity sensor with directionally aligned porous structure for substantially enhancing both sensitivity and response speed

Abstract

In response to the growing demand for wearable devices and environmental monitoring, this study presents a novel fabrication method for directionally aligned CNFs/MWCNTs aerogel film (AGF), thereby achieving high-performance, flexible humidity sensors with rapid response and excellent mechanical properties. By combining freeze-drying and directional freezing techniques, an ordered porous structure within the AGF was created to promote efficient water molecule exchange and optimized conductivity. The sensor sensitivity was fine-tuned by adjusting the MWCNTs content, reaching a peak response of 71.5% (ΔI/I0) at 75% RH, with response and recovery times of 18 s and 47 s, respectively. This surpasses the performance of traditional sensors based on CNFs/MWCNTs. Upon evaluating the mechanical properties of AGF, it was found that they possessed outstanding flexibility and bending resistance, making them highly suitable for wearable electronic applications. The versatility of AGF sensors was demonstrated in various humidity monitoring scenarios, such as close-range positioning of moist objects and real-time human breathing monitoring. To showcase practical applicability, an STM32-based smart wireless humidity monitoring system suitable for real-time data collection, remote monitoring, and flexible installation was developed. Moreover, this fabrication method holds vast potential in various application fields, including wearable devices, environmental monitoring, and electronic skin.