An anti-freezing and anti-drying nanocellulose hydrogel for human motion detection

Abstract

Flexible sensors based on biological hydrogels have gained significant attention in the fields of wearable devices, human-computer interaction robots, and medical monitoring. Nanocellulose, a natural polymer material, offers advantages such as low cost, abundant reserves, green environmental protection, and renewability. However, the high water content of the nanocellulose-based flexible sensor limits its application at low temperatures, making it difficult for the nanocellulose-based hydrogel electronic skin to function properly. To enhance the hydrogel's anti-freezing and anti-drying properties, we introduced glycerol (GL) into the in-situ grown polypyrrole (PPy) hydrogel of 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized cellulose nanofibril (TOCN) and obtained the organic hydrogel TOCN/PPy/GL. The prepared TOCN/PPy/GL organic hydrogel maintains excellent electrical conductivity, mechanical properties, and strain sensing capabilities (strain sensitivity GF=2.41 at −45 ℃, response time 100 ms, recovery time 200 ms). The TOCN/PPy/GL organic hydrogel electronic skin also exhibited exceptional anti-drying property, with a volume retention of 66.75% after 24 h at 100 ℃, which is six times higher than the volume retention of TOCN/PPy hydrogel without GL under the same conditions.