A novel flexible humidity switch material based on multi-walled carbon nanotube/polyvinyl alcohol composite yarn

• A flexible humidity switch material with adjusted switch point from 75% to 85% RH is fabricated by dipping the MWCNT yarn in various PVA solutions.
• The sensitivity of the composite yarn can reach up to 1.89 at 100% RH, much higher than 0.3 reported in literature.
• The humidity sensing material demonstrates excellent repeatability and stability, acceptable hysteresis and response time.

A yarn-like switch-type humidity sensing material is fabricated by infiltrating hydrophilic water-swellable polyvinyl alcohol (PVA) into a multi-walled carbon nanotube (MWCNT) yarn. The electrical resistance of the virgin humidity sensing material remains almost constant at low relative humidity (RH), and then increases sharply as the RH increases above 75%, showing a good humidity switch characteristic. The sensitivity of the sensing material can reach up to 1.89 at 100% RH. The flexible humidity sensing material shows an adjustable switch point (between 75% and 84% RH), excellent reproducibility, moderate hysteresis, and sufficiently high residual sensitivity (0.63) for repeated use. The promising multi-functional material may be used for real-time RH switch monitoring in flexible electronic devices, such as in intelligent textiles and other industrial applications.