Fig. 2: Direct extrusion printing of HAMA constructs and their shrinking behaviors.

a Schematics showing the concept of shrinking printing, where a printed hydrogel structure is post-treated to reduce its size and achieve higher resolution. b, c Printability mapping of HAMA inks at different concentrations and extrusion pressures. d Photographs (upper) and micrographs (lower) showing size changes of printed HAMA hexagons (2.0 w/v%) immersed in 2.0 w/v% HM_w chitosan dissolved in 1.0 v/v% acetic acid aqueous solution during the 24h shrinking process. e, f Corresponding quantitative analyses of size changes of the printed HAMA hexagons (2.0 w/v%), include e side-to-side distance and f thickness, during the 24h shrinking process. g Photographs (upper) and micrographs (lower) showing size changes of printed HAMA hexagons (2.0 w/v%) at 2 h and 24 h of shrinking in different concentrations of HM_w chitosan (0.5–5.0 w/v%) dissolved in 1.0 v/v% acetic acid aqueous solution, h, i Corresponding quantitative analyses of size changes in h side-to-side distance and i thickness. j Vector-field maps comparing the 24-h shrinking images (magenta) to the corresponding 2-h shrinking images (green) by a B-spline-based non-rigid registration algorithm, where the overlaps appear in white and the grids show local distortions. Note that the 2-h shrinking images have been rescaled to match the sizes of the 24-h shrinking images to enable comparisons. **P < 0.01; one-way ANOVA (e, f, compared with the values of corresponding as-prepared samples); mean ± s.d. (e, f, n = 40; h, i, n = 10).