In-situ synthesis of biomimetic eutectogel sensors exhibiting softness, strain-stiffening, and anti-fatigue properties via a hierarchical bonding strategy

Balancing softness with mechanical robustness remains a critical challenge in synthetic electronic sensors, restricting their practical utility. Herein, we propose a strain-stiffening eutectogel fabrication strategy featuring a biomimetic hierarchical bonding design inspired by mammalian skin. This system (DES-PAA@Al, deep eutectic solvent-polyacrylic gel) integrates weak intermolecular interactions for compliance ( E 1  = 2.9 × 10 −4  MPa/%) and robust Al 3+ -carboxyl coordination bonds within the PAA network to ensure structural integrity under extreme deformation. The optimized eutectogel achieves ultrafast gelation (<20 s) and a sevenfold modulus enhancement ( E 3 / E 1  = 7), synergistically combining ultra-stretchability ( λ  = 1060 %), fatigue resistance (850 cycles), high sensitivity (gauge factor ( GF ) = 1.17), strain-stiffening behavior, and broad environmental adaptability (−60 °C to 80 °C). Mechanical testing, internal structural evaluation, and computational simulations elucidate the hierarchical bonding mechanism, revealing energy-dependent bonding interactions. These capabilities enable the eutectogel to gently conform to rough surfaces while maintaining durability, making it ideal for electronic skin (e-skin) applications. This work establishes a universal and facile in-situ approach for fabricating skin-like strain-stiffening eutectogels, advancing their potential in bioelectronic interfaces such as strain-resistive sensors and physiological signal monitoring (e.g., Electrocardiogram (ECG)).