Unveiling linear and nonlinear viscoelastic fingerprints of CMC/alginate polysaccharide hydrogels via FT-rheology:...

Although polyelectrolyte hydrogels such as sodium alginate and carboxymethyl cellulose (CMC) are widely used in bioprinting, the correlation between their nonlinear viscoelastic behavior and 3D extrusion printability has not yet been fully established. This study investigates this relationship in depth, demonstrating that pure CMC hydrogels exhibit exceptional stability for over 24 h, but the addition of alginate compromises post-printing geometric stability. To understand this phenomenon, we employed Fourier Transform Rheology (FT-rheology) from Large Amplitude Oscillatory Shear (LAOS) measurements, which revealed a unique molecular rheological signature for each formulation. The specific harmonic profile of pure CMC acts as an indicator of an ideal combination of stress relaxation and structural recovery, directly correlating with its superior printability. This approach not only justifies the choice of pure CMC for applications requiring high 3D shape stability but also establishes FT-rheology as a powerful and predictive tool for hydrogel optimization, enabling the rational design of materials with the desired balance between mechanical stability and functionality.