A microgel-integrated strategy enabling DIW-printable PVA bioinks through GelMS-driven rheology modulation

Direct ink writing (DIW) of hydrogel scaffolds requires inks that can be easily extruded through nozzles while rapidly recovering sufficient elasticity to maintain shape fidelity after deposition. Here, we propose a microgel-integrated strategy to formulate DIW-printable poly(vinyl alcohol) (PVA) bioinks by dispersing chemically crosslinked gelatin microspheres (GelMS) into a continuous PVA matrix. The GelMS were prepared via water-in-oil emulsification, yielding microspherical building blocks with a median diameter of approximately 13 μm. The resulting GelMS/PVA bioinks exhibited a well-defined printability window, with apparent yielding behavior, pronounced shear-thinning, and rapid thixotropic recovery. The apparent yield stresses of g16% and g18% reached approximately 325 Pa and 690 Pa, respectively, enabling a favorable balance between extrudability and post-deposition stability. The power-law fitting and finite element simulation correlated the rheological properties with nozzle flow fields, where the maximum outlet velocity of g16% reached approximately 6.9 mm/s under 1 bar. After printing, the freeze–thaw cycling could physically crosslink the PVA matrix through crystallite formation, producing mechanically robust and dimensionally stable hydrogels with restricted swelling. This strategy could be extended to alginate and chitosan microgel systems and supported model payload compartmentalization and sustained release. The qualitative extract-based assays further indicated good cytocompatibility, highlighting the potential of GelMS/PVA microgel bioinks for soft tissue engineering applications.