A superstretchable and ultratough hierarchical fluorescent hydrogel with antioxidant and antimicrobial activity for...

Product counterfeiting and Food spoilage present severe challenges to global supply chains, necessitating advanced packaging that ensures both safety and authenticity. Herein, we report a highly robust, multi-functional double-network hydrogel for advanced information encryption and real-time freshness monitoring. The hierarchical matrix integrates a covalent poly(acrylamide-co-gelatin methacrylate) network with an ionic calcium alginate network, critically reinforced by tannic acid (TA) acting as a molecular glue. This architecture endows the hydrogel with an extraordinary breaking elongation of ∼4250%, an exceptional toughness of ∼154 MJ/m³, and a high tearing energy of ∼1.7 kJ/m². Furthermore, the controlled release of TA provides reliable, broad-spectrum tissue-level adhesiveness, alongside potent antioxidant and antimicrobial activities (near 100% bactericidal rate within 24 h). By embedding NH₃-responsive carbon dots, the hydrogel exhibits distinct, reversible fluorescence shifts, enabling sophisticated, multi-tiered anticounterfeiting applications including erasable Morse code, mathematical matrices, and dynamic QR codes. Meanwhile, the fluorescent hydrogel sensor accurately mapped the real-time spoilage of tilefish at both 25 °C and 4 °C, demonstrating a near-perfect correlation (R² ≥ 0.995) between Total Volatile Basic Nitrogen (TVB-N) accumulation and colorimetric variance (ΔE). This dual-functional hydrogel offers a highly promising platform for next-generation intelligent and active food packaging.