Fig. 4: Lateral printing resolution analysis.
a The spoke-like pattern employed to evaluate the printing resolution, showing the increased gap between adjacent spokes from the centre to the periphery. Resolution is characterised by the unresolved fraction, defined as the ratio between the unresolved diameter (red dashed circle) and the outer diameter. b Fluorescent image of the cell-laden structure. c Microscopic images of printed structures, showing the unresolved areas (red dashed circles) as a function of relative exposure energy for pure PEG-GelMA bioink (upper) and those added with tartrazine (middle) and Cur-Na (bottom). Er is the relative energy defined as the ratio between the actual light energy and the unit exposure dose. Images b and c are representatives of n = 3 independent experiments. d Quantitative relation of unresolved fraction against exposure energy. A. U. standards for arbitrary units, a relative unit of measurement to represent the ratio of quantities. n = 3 independent samples. e Printing window of Cur-Na showing the exposure energy range within which the resolution is maintained. The grey, red and blue-shaded areas indicate the window width of 1 mM, 2 mM and 3 mM Cur-Na, respectively. n = 3 independent samples. f Quantitative relation of unresolved fraction against exposure energy for cell-laden structures. n = 3 independent samples. Data are presented as mean ± standard deviation. All scale bars indicate 1 mm.
