## 3 Results  
The results of the geometrical characterization of ten scaffolds printed on different days are shown as boxplots in Figure 3, demonstrating mean pore sizes of about 800 \(\pm\) 52 \(\upmu\)m in the xy plane and 197 \(\pm\) 20 \(\upmu\)m in the z direction. The mean thickness of the struts was 143 \(\pm\) 26 \(\upmu\)m and the nodes areas showed a mean diameter of 338 \(\pm\) 43 \(\upmu\)m.  
Figure 2: Geometrical structure of numerical model: (**a**) Exemplary structure of a model with five pores in \(x\) direction (\(number\_x=5\)) and three pores each in \(y\) and \(z\) direction (\(number\_y=number\_z=3\)); (**b**) Comparison of fabricated PCL scaffold and numerical FEM model. Overall, six PCL samples were tensile tested. The mean Young's modulus of the PCL was 566 \(\pm\) 45 N/mm\({}^{2}\), the mean yield strength was determined to be 17.9 \(\pm\) 1.0 N/mm\({}^{2}\), and the mean strain at yield strength was 8.8 + 2.1%. Associated stress-strain diagrams are provided in Figure 4.  
The resulting Prony terms of the creep testing with a duration of 27 h are provided in Table 2.  
PCL scaffolds show an almost linear-elastic behavior up to tensile strains of 3%. From an elongation of 5% stress, the data show a plastic behavior. The mechanical behavior of PCL scaffolds is shown in Figure 5. \begin{table}
\begin{tabular}{c c c} \hline
**Prony Link** & **Value [Pa]** & **Relaxation Time [sec]** \\ \hline
1 & \(1.401\times 10^{9}\) & \(1.299\times 10^{-2}\) \\
2 & \(3.979\times 10^{7}\) & \(3.841\times 10^{-1}\) \\
3 & \(4.052\times 10^{7}\) & \(1.780\) \\
4 & \(4.054\times 10^{7}\) & \(8.621\) \\
5 & \(3.828\times 10^{7}\) & \(2.839\times 10^{1}\) \\
6 & \(1.116\times 10^{8}\) & \(6.884\times 10^{2}\) \\
7 & \(5.326\times 10^{7}\) & \(1.031\times 10^{2}\) \\
8 & \(8.122\times 10^{8}\) & \(7.879\times 10^{3}\) \\
9 & \(9.509\times 10^{7}\) & \(1.511\times 10^{5}\) \\ \hline \end{tabular}
\end{table} 
Table 2: Prony terms of PCL. Pa = Pascal, sec = seconds. Figure 4: Material characteristics of PCL specimens (n = 6). Figure 3: Geometrical characterization of PCL scaffolds. d\({}_{n}\): Diameter of PCL struts in node areas; d\({}_{3}\): Diameter of PCL struts in areas distant from nodes; a\({}_{xy}\): Clear width between two struts in xy plane; a\({}_{x}\): Clear width between two struts in z direction. Numerical calculations based on Timoshenko Beam188 elements (element sizes: a_xy/16) show valid results with a force ratio of \(\overline{\mu}_{sum}=1.0515\) (\(\overline{\mu}_{0.01}=1.0049\), \(\overline{\mu}_{0.02}=1.0412\), \(\overline{\mu}_{0.03}=1.1083\)). Thereby, the numerical results show stable results, independent of the implemented element types (rods vs. beams), grade of element functions (Beam188 vs. Beam189), size of elements and material laws (viscoelastic vs. elastic-plastic). The related data are provided in Supplementary Table S2. The parameters of numerical models can be varied. Figure 6 shows exemplary effects of strut thicknesses on numerical results. Studies with electronic microscopes show continuous collagen cover layers on all struts of PCL scaffolds. This is illustrated in Figure 7, showing, on the left side, a PCL scaffold before collagen coating and, on the right side, a PCL scaffold after coating. Without treatment  
Figure 5: Mechanical behavior of PCL scaffolds. Top: PCL scaffold before and after tension load. Bottom: Force–Strain diagram. Figure 6: Effect on strut thickness on mechanical behavior of PCL scaffolds (viscoelastic FEM model). with plasma devices, no collagen coating could be achieved due to less adherence on the PCL surface. MG63 cells, MLO-Y4 cells and MSC were marked via Giemsa staining on all PCL scaffold struts after three days of incubation, illustrated in Figure 8. MG63 cells exhibited the highest cell density on scaffolds. In preliminary tests, no cell growth was observed on specimens not coated with collagen.