Thermoplastic polyamide elastomer based flexible humidity sensor for breath monitoring

Nowadays, there are many researches on flexible humidity sensors based on different composites, such as polymer with graphene oxide, carbon nanotubes as conductive fillers. Herein, a flexible wearable device used for humidity detection and breath monitoring was fabricated based on the molecular designable thermoplastic polyamide elastomer (TPAE). TPAE is block copolymers consisting of the polyamide hard segments and the polyether soft segments. Among them, the hard segments (PA1212 or PA6) form the crosslinking network providing resilience, and the soft segments composed of PPO and PEO endow TPAE with flexibility and solvent-responsiveness. The resistance of TPAE-based humidity sensor decreases with the increase of relative humidity (RH), exhibiting negative humidity sensitivity. Besides, it has a wide humidity monitoring range (11 %RH similar to 91 %RH) and good fitting degree of R-2 > 0.99 which is hardly influenced by bending deformation. When the humidity sensor was exposed to organic vapor (e.g. ethanol), it exhibited a faster response of astonishing 4 s. This novel block copolymer not only shows good humidity sensing performance in many aspects, but also provides a novel strategy and approach for the preparation of the humidity sensing materials afterwards.