The Influence of Rheological and Wetting Properties of Hydrogel-based Bio-Inks on Extrusion-based Bioprinting

The wall slip and flow behavior of alginate as well as gelatin based hydrogels with respect to the impact of these rheological and wetting properties on extrusion-based bioprinting (EBB) was investigated. Capillary rheometry and printing tests indicate that slip is negligible at high stresses relevant for EBB, i.e., well above the hydrogels yield stress. On the contrary, rotational rheometry performed at low shear stresses revealed that alginate hydrogels present much stronger slip than gelatin gels, irrespective of crosslinker and polymer concentration. This result is presumably due to the formation of a heterogeneous microstructure for alginate gels and has an unfavorable impact on the printing quality with the production of large fluctuations in line width and higher line spread ratio.