Hydrotalcite-Reinforced Triple-Network Multifunctional Hydrogels via Dynamic Imine/Borate Bonds: Wearable Sensing and Selective VOC Adsorption

Polymer hydrogels have attracted significant attention for flexible wearable devices due to their facile fabrication and excellent environmental compatibility. However, conventional hydrogels often suffer from insufficient mechanical strength and comprehensive performance. To meet practical requirements for hydrogel strain sensors, achieving simultaneous high conductivity, frost resistance, and proper adhesion remains a critical challenge. Based on the fact that inorganic compounds can enhance mechanical strength, the inorganic hydrotalcite (HT) has been incorporated in this study to improve the mechanical properties of hydrogel through multiple, multilevel and strong interfacial interactions. The addition of lithium chloride (LiCl) and dimethyl sulfoxide (DMSO) imparts exceptional frost resistance, while LiCl simultaneously enhances electrical conductivity. By integrating N-(2-hydroxyethyl)acrylamide (HEAA), sodium alginate (SA), polyethylenimine-4-acetophenylboric acid (PEI-APBS), and tannic acid (TA), a hydrotalcite-based organic–inorganic triple network (HOITN) hydrogel was successfully fabricated via a one-pot method. As a wearable strain sensor, it showed high sensitivity (GF = 1.0–2.4) over a broad strain range (0–900%) with fast response/recovery times (93/102 ms), enabling reliable monitoring of both large joint movements and subtle physiological signals. Furthermore, the hydrogel exhibited selective adsorption of volatile organic compounds (VOCs), with adsorption capacities of 1.4 g/g for acetone, 2.0 g/g for methanol, and 1.2 g/g for ethanol. This multifunctional hydrogel presents great potential for applications in flexible electronics, low-temperature sensors, and environmental remediation.