Patterned, flexible, self-supporting humidity sensor with core-sheath structure for real-time sensing of human-related humidity

Abstract

Self-supported nanofiber membranes were fabricated by the rhombus-patterned collector in the electrospinning process in this work. The rhombus nanofiber networks were used to retain the mechanical flexibility of the device and stable responses such as bending and winding deformation. A resistive humidity sensor was developed by applying hydrophilic PANI with varying contents onto nanofiber surfaces through in situ polymerization, serving as electrodes. In this context, the self-supported membranes serve dual roles as both the sensing material and the substrate for the sensor. A comprehensive assessment was conducted to analyze how variations in relative humidity affect the sensing characteristics of the acquired sensors. By facilely regulating the ratio of dopant and oxidant concentration to monomer concentration in the polymerization process, the response of the sensors was increased from 49% to 83% with increasing relative humidity from 13 to 93%, good linearity (R2 = 0.97) and a short response/recovery times (33/88s). The prepared sensors exhibited appreciable mechanical properties and showed outstanding stability after 1000 cycles of bending and the resistances only slightly increased by 2.5%. Moreover, the sensor can monitor both human respiration and non-contact skin humidity. Its exceptional performance makes it easily integrable into textiles for the creation of wearable electronics.