Unveiling rheological behavior of hydrogels toward Magic 3D printing patterns

Hydrogels, characterized by their three-dimensional network structure and exceptional hydrophilicity, are versatile materials used in fields such as biomedicine, flexible electronics, and intelligent packaging due to their biocompatibility, electrical conductivity, and mechanical adaptability. This review explores the integration of hydrogels with 3D printing technologies, addressing their unique rheological properties, substrate characteristics, and their impact on the precision and stability of printed structures. 3D printing patterns, including stereolithography, digital light processing, two-photon polymerization, direct ink writing, and inkjet printing, are evaluated for their resolution, adaptability, and material requirements. The paper also examines how the mechanical and chemical properties of natural, synthetic, and composite hydrogel ingredients influence printability and application potential. Rheological behaviors, such as viscosity, shear-thinning, yield stress, and viscoelasticity, are identified as key determinants of successful 3D printing outcomes. Benefiting from the obvious merits, 3D-printed hydrogels are widely applied in areas like tissue engineering, soft robotics, electronics, and food packaging. The findings underscore the need for continued research into enhancing hydrogel performance and expanding the capabilities of 3D printing techniques.