Programmable Anisotropic Hydrogels for Biomedicine: From Precise Design to Advanced Applications

Anisotropic hydrogels have emerged as a groundbreaking class of biomaterials, exhibiting remarkable potential in biomedical applications owing to their directionally dependent physical, chemical, and biological properties. This review comprehensively explores recent advancements in the design, fabrication, and functional applications of biomedical anisotropic hydrogels, with a focus on their unique structural and performance characteristics. We systematically analyze both natural and synthetic polymer matrices, highlighting key materials such as chitosan, sodium alginate, and polyacrylamide, and their roles in achieving tailored mechanical, electrical, and biocompatible properties. Advanced preparation techniques, including template-directed synthesis, external field-driven methods (e.g., electric, magnetic, and shear fields), and 3D printing, are critically evaluated for their ability to precisely engineer anisotropic microstructures. Furthermore, we discuss cutting-edge testing methodologies to characterize these hydrogels, emphasizing microscopic imaging, mechanical rheology, and biosafety assessments. The intelligent responsiveness of anisotropic hydrogels to stimuli such as light, temperature, and pH is also examined, showcasing their adaptability for dynamic applications. Finally, we highlight their potential in tissue engineering, drug delivery, wound dressing, and health monitoring, while addressing current challenges and future prospects. This review underscores the pivotal role of interdisciplinary collaboration in advancing anisotropic hydrogels toward clinical translation and next-generation biomedical innovations.