Healable and Transparent Ionic Conductive Hydrogels Based on PNATF as Multiple-Signal Sensors

In recent years, flexible wearable technology has been extensively utilized in health monitoring due to its capabilities of acquiring multiple signals and transmitting data wirelessly in real time. Ionic conductive hydrogels have already played an important role in the field of flexible wearable devices depending on their excellent biocompatibility, mechanical adaptability, and transparency. In this study, a multiresponsive ionic conductive hydrogel with both superior mechanical properties and self-healing ability was constructed through the interwoven network structure. The basic skeleton is formed by N-isopropylacrylamide and acrylic acid (PNIPAM/PAA) through co-cross-linking. The final interwoven structure is constructed by the network of ethylenediaminetetraacetic acid ferric (III) sodium salt cross-linked with tannic acid (TA) interpenetrating with the basic backbone. The stretchability of up to 2638% can be achieved due to the dynamic hydrogen bonding between the PNIPAM/PAA skeleton and TA. Meanwhile, the abundant catechol groups of TA endow the hydrogel with an adhesion strength of 7.06 kPa, and it can be easily peeled off without any residue when applied to the human skin. The stable mechanical cycling performance, outstanding self-healing ability, electrical conductivity (1.28 S·m–1), and sensitivity (GF = 4.368) of the hydrogel are attributed to the reversible coordination of Fe3+. Based on the above comprehensive performance, the ionic conductive hydrogel designed in this study will have great application potential as a temperature-sensitive sensor in monitoring human movement and environmental temperatures, which also provides a unique perspective for the detection of fever and abnormal thermotherapy.