Lanthanide‐Coordinated Multifunctional Hydrogel for Detecting Human Motion and Encrypting Information

Abstract Smart hydrogels with multi‐fluorescent properties hold great promise for information encryption. However, conventional fluorescent hydrogels often lack adequate mechanical properties and multiple responsiveness, limiting their range of applications. In this study, a multifunctional hydrogel featuring an interpenetrating polymer network (IPN) composed of poly(vinyl alcohol) (PVA) and poly(acrylic amide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) P(AM/AMPS) chemical cross‐linking networks is designed. Through the coordination of lanthanide ions (Eu ³⁺ , Tb ³⁺ ) and glycine, the hydrogel achieves exceptional stretchability (over 900%) and adjustable photoluminescence properties. Due to the sulfonic acid groups on 2‐acrylamide‐2‐methylpropanesulfonic acid (AMPS), which support various noncovalent interactions, the PVA‐P(AM/AMPS)‐Gly‐Ln ³⁺ hydrogel displays strong and reversible adhesive properties on diverse substrates. Ultimately, the hydrogel is assembled into a multifunctional, flexible sensor, boasting satisfactory sensitivity (GF = 5.3), rapid response rate (100 ms), and outstanding photoluminescence characteristics, highlighting its potential for applications in human motion detection and information encryption.