Tannic Acid‐Modified Cellulose Nanofiber Reinforced Polymerizable Eutectogels for High‐Performance Stretchable Strain Sensors

Eutectogels derived from deep eutectic solvents (DESs) integrate the advantages of hydrogels and ionogels and have emerged as promising materials for flexible electronics. However, achieving high mechanical robustness, environmental adaptability, and multifunctionality within a single eutectogel system remains challenging. Herein, we report a polymerizable DES platform (CA‐DES) constructed from a citric acid quaternary ammonium salt derivative (CACl) and acrylic acid, which serve as hydrogen‐bonding components, while acrylic acid further acts as the polymerizable monomer. To reinforce the network architecture, tannic acid‐modified carboxylated cellulose nanofibers are introduced, enabling interpenetrating structures through physical and chemical crosslinking. The resulting CAT eutectogel series exhibits mechanical and functional properties, including ultrahigh stretchability (up to 2483%), wide temperature tolerance (−32.7 –80°C), high ionic conductivity (up to 3.13 ± 0.02 mS cm −1 ), strong adhesion (≈ 236.9 N m −1 ), rapid self‐healing (up to 99.6%), and antibacterial and biocompatible characteristics. The optimized CA5T10 eutectogel enables a wearable strain sensor with a broad sensing range (∼1000% strain), high sensitivity (gauge factor = 7.82), fast response (170 ms), and robust performance under torsional deformation and puncture damage. This work establishes a multifunctional polymerizable eutectogel platform and provides a versatile design strategy for next‐generation strain sensors and wearable electronics.