A humidity‐sensing composite microfiber based on moisture‐induced swelling of an agarose polymer matrix

Herein, we present a humidity sensing microfiber based on an agarose polymer as a hydrophilic matrix and carbon nanotubes (CNT) as conducting fillers. The humidity‐dependent resistance is the key property of the composite microfiber as a humidity sensor. The composite microfiber composed of the agarose matrix swells or contracts depending on environmental humidity, leading to changes in junction density between the carbon nanotube conducting fillers inside the fiber. Moreover, adsorption of water molecules on the CNT filler could further increase the resistance of the microfiber sensor. The real‐time resistance monitoring of the microfiber shows reliable and reversible response to the repetitive changes in relative humidity with reasonable response rate. The tensile strength test confirms the mechanical robustness of the composite microfiber. The fabrication process is facile and presumably scalable. Such a practical fiber sensor could be readily used as a humidity‐sensing component in smart textile and wearable devices. POLYM. COMPOS., 40:3582–3587, 2019. © 2019 Society of Plastics Engineers