Integrating Strength and Toughness into a Hierarchically Heterogeneous Hydrogel

• • Tensile strength of 55.3 MPa and toughness of 1031 MJ m⁻³ simultaneously achieved, exceeding the fracture energy-modulus trade-off line (Γ = 234.234 kN³/² m⁻² × E⁻¹/²) by a significant margin, enabling load-bearing implants and structural soft robotics. • • Stretchability of 3300% with stiffness of 6.8 MPa, a combination that outperforms natural materials such as cartilage (≈0.5–1.0 MPa modulus) and synthetic tough hydrogels, critical for artificial muscles requiring high actuation strain and mechanical resilience. • • Regeneration capability demonstrated over 10 cycles with retained mechanical integrity, and adhesive joints (50 mm² area) supporting 5 kg (≈0.1 MPa shear strength), addressing the need for reusable, self-healing interfaces in soft robotics and tissue adhesives. • • Hierarchical core-sheath architecture with seamless interfaces eliminates stress concentration, as evidenced by the absence of premature failure in tensile tests up to 3300% strain, providing a scalable design rule for heterogeneous hydrogels with density gradients.