High sensitive humidity sensor based on PEDOT:PSS/CMC-Na coated polyester fabric with directional moisture transport performance

Flexible humidity sensors with excellent flexibility and sensitivity have been widely used in various fields such as human and plant health monitoring and management, non-contact human-machine interaction, smart e-textiles, and industrial and agricultural production. However, many sensors are limited their application due to the problems of unbreathable and poor wear comfort. Herein, a highly sensitive humidity sensor based on flexible polyester fabric with directional moisture transport is proposed. The facile method of coating is conducted by the preparation of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and sodium carboxymethylcellulose (CMC-Na) paste with adjustable content and applied to the polyester fabric. The difference of hydrophilicity between the two sides of the fabric caused by the coating helps to directional moisture transport, thus giving rapid sensitivity, while using PEDOT: PSS can obtain the changes of electrical conductivity coming from the humidity. and the addition of CMC-Na not only helps the coating, but also provides hydrophilic groups, which is conducive to humidity sensing and directional moisture transport. The combination of this moisture-sensitive coating and directional moisture transport gives the sensor a fast humidity response time of 0.35 s, a wide humidity detection range (0‐100%(0–100% RH) and sensitivity of 4.15. Furthermore, the sensor can maintain the humidity response time in milliseconds even after being subjected to water washing and friction, indicating its excellent durability and stability.