A metal–organic framework enhanced single network organohydrogel with superior low-temperature adaptability and UV-blocking capability towards human-motion sensing

Abstract

In recent years, hydrogel-based wearable smart electronic devices have attracted much interest. However, it still remains crucial to integrate multiple functions into a single hydrogel in order to further develop such devices. Herein, a highly stretchable and mechanically toughened metal–organic framework (MOF)-based single network organohydrogel with superior low-temperature adaptability and UV-blocking capability is developed by using UiO-66-NH₂ as the reinforced nanofiller in polyacrylic acid networks containing a glycerol/water binary solvent system. UiO-66-NH₂ nanoparticles significantly enhanced the mechanical properties of the as-prepared organohydrogel by forming hydrogen bonds with copolymer chains, and its tensile strength is 2.9 times that of a pure organohydrogel. The incorporation of glycerol serving as an anti-freezing agent effectively impedes the formation of ice crystals, thereby endowing the MOF-based organohydrogel with extraordinary low-temperature tolerant ability as low as −40 °C. Meanwhile, this organohydrogel exhibits excellent strain sensitivity (GF = 2.4), fast strain response (577 ms) and wide strain detection range (0–800%), and can be assembled as a reliable flexible strain sensor to precisely monitor different physical deformations and complex human movements. Impressively, combined with the international universal Morse code, the developed MOF-based organohydrogel sensor also exhibits an attractive feature that can serve as a freezing-tolerant communication device for encrypting and transmitting various messages (e.g., “Safe”, “Dangerous” and “I will arrive on time”) even under extremely cold environments. This work demonstrates the significant potential of metal–organic framework reinforced low-temperature tolerant organohydrogels in flexible electronic devices.