A study of the temperature-dependent stress yielding behavior of a gelatin-based hydrogel ink and its effects on the enhancement of the 3D printing resolution

Though existing studies had continuously improved the hydrogel printing resolution by facilitating ink solidification, it was literally challenging to exceed the size limit of the printing needle even if there was an ideal ink that could solidify instantaneously. One possible solution to this hurdle is to stretch the hydrogel ink with a high printing speed and try maintaining its deformation without strain recovery. In this study, a gelatin/alginate/hydroxyapatite(HA) ink was printed at multiple temperatures, and a much lower yielding strain occurred at -1°C than 2-5°C according to our rheological tests. At -1 °C, the hydrogel ink could be highly stretched to produce an ultrahigh resolution at 81±13μm while maintaining uniform and continuous. Furthermore, our biological tests found a high scaffold resolution greatly promoted cell adhesion, proliferation, osteogenic differentiation and biomineralization. We stepped further from existing studies, by coming up with a new concept of utilizing ink stress-yielding in improving printing resolution, which would broaden our understanding to the processing-structure-property relationship in hydrogel-based 3D printing.