Highly transparent, ultra-tough, and environmentally adaptive cellulose-based double-network eutectogel for flexible strain sensor

To address the problems of poor mechanical properties and strong hygroscopicity of the existing eutectogels, this study presents a novel eutectogel containing carboxymethyl cellulose (CMC) designed for wearable strain-sensing applications. The gel was synthesized via a rapid photopolymerization strategy using a choline chloride-urea deep eutectic solvent to dissolve CMC, combined with hydroxyethyl acrylamide as the monomer and phytic acid as a multifunctional crosslinker. The optimized eutectogel exhibited exceptional high stretchability (1189% strain), tensile strength (1166 kPa), and toughness (6.1 MJ/m 3 ), alongside remarkable optical transparency (91% transmittance). The incorporation of phytic acid enhanced hydrogen-bonded crosslinking, enabling self-healing within 3.2 s. The dual ionic/protonic conductive network endowed the gel with high strain sensitivity (gauge factor: 8.81 at 150–300% strain) and temperature resilience, maintaining stability across a wide temperature range (−20 to 60 °C). Unlike conventional hydrogels, this eutectogel demonstrated superior environmental stability, with minimal weight fluctuation (±4%) after 7 days under ambient conditions. This eutectogel-based flexible sensor can monitor both large joint movements (e.g., knee bending) and subtle muscle activities (e.g., facial expressions). This work provides a construction strategy of eutectogel by integrating green chemistry, multifunctional performance, and scalable fabrication, offering a promising platform for durable, high-sensitivity wearable electronics.