Search

Real‐time monitoring of respiration plays a very important role in human health assessment, especially in monitoring and analyzing respiration during exercise and sleep. However, traditional humidity sensors still have problems in flexibility, sensitivity, and durability, so there is an urgent need to develop humidity sensors with high sensitivity, stretchability, and environmental resistance as respiratory monitoring applications. Here, based on the double network hydrogel structure of polyvinyl alcohol and polyacrylamide, a highly sensitive, highly stretchable, and environmentally stable organic hydrogel humidity sensor has been manufactured by using the synergistic effect of lithium chloride and MXene. The hydrogel humidity sensor shows rapid response in the humidity range of 40–85% RH, and has a high sensitivity of −103.4%/% RH. In addition, it exhibits more than 3000% mechanical strain and excellent environmental resistance, which is attributed to the chemical cross‐linking in the hydrogel network and the synergistic effect of multiple hydroxyl groups in glycerol forming rich hydrogen bonds with water and polymer chains. The hydrogel humidity sensor is used for real‐time monitoring of breathing and sleep processes. This work provides a new strategy for preparing high‐performance, extensibility, and environmental stability hydrogel‐based sensors for respiratory monitoring. [ABSTRACT FROM AUTHOR]

A simple and mildly rapid preparation strategy is developed to accelerate polymerization by UV-induced excitation of ferric phytate ligands and generation of free radicals by electron transfer. The introduction of phytic acid provides a synergy between excellent electrical conductivity and anti-freezing the hydrogel through ionization and hydrogen bonding, which enables hydrogel-based strain sensors to show great potential for stable detection of physiological activities in low-temperature environments. [Display omitted] • Anti-freezing, ion-conducting and stretchable hydrogels are developed. • A rapid gelation process in 90s with UV induced iron phytate. • The hydrogel shows good sensing properties at −30℃ with 97% gauge factor retention. • A novel hydrogel-based temperature control switch is demonstrated. Conductive hydrogels have great potential in flexible electronics due to their flexibility, excellent biocompatibility and diverse functionalities. However, most rapid-gelation hydrogels tend to manifest weak and fragile due to vigorous reaction process and poor adaptability in cryogenic environment, which severely impede their practical applications. Herein, a facile and mild strategy for rapid gelation is proposed that accelerates polymerization by generating reactive oxygen radicals via electron transfer based on the excitation of ferric phytate ligands under UV irradiation, which takes only 17 s to initiate. Interestingly, the introduced phytic acid imparts the hydrogel excellent electrical conductivity (12 ms/cm), frost resistance (−31℃) and improves tensile properties (elongation at break 1299 %). The hydrogel that combines the above merits inspires the construction of strain sensor for monitoring physiological activity of low-temperature environments. This study provides a simple and universal approach for the rapid preparation of antifreeze hydrogels and reinforces the focus on sustainable and high-value utilization of phytic acid in advanced applications. [ABSTRACT FROM AUTHOR]