Water Transport‐Modulated Highly Compressive Hydrogel for Total Biomimetic Sensing Intervertebral Disc

Abstract Degenerative disc disease (DDD) affects millions globally, with artificial total disc replacement (A‐TDR) emerging as a key surgical intervention to restore spinal function and mobility. Current implantable prostheses incorporating multi‐component architectures to replicate the functional heterogeneity of natural intervertebral discs (IVD) face challenges in achieving mechanical and physiological compatibility. Inspired by the natural IVD's structure, where a soft nucleus pulposus (NP) is encased by a tough annulus fibrosus (AF), a water transport‐modulated directional annealing casting (DAC) approach has been developed to construct bulk hydrogels with tunable mechanical properties (up to ≈36.69 MPa compressive strength with ≈5.35 MPa modulus). This strategy enables the fabrication of an integrated hydrogel‐based IVD (H‐IVD) with biomechanically gradient structures, featuring a high‐strength AF region (compressive modulus ≈2.77 MPa) seamlessly transitioning to a compliant NP core (modulus ≈0.26 MPa) while maintaining physiological water content throughout. The H‐IVD exhibits excellent biocompatibility and load‐bearing capacity, with inherent stress‐sensing capabilities enabling dynamic functional assessment of spinal biomechanics. Furthermore, this integrated design strategy demonstrates broad applicability for engineering various dimensionally‐controlled biomimetic tissues, from simple 1D structures to complex 3D organs requiring precise spatial control of material properties.