## 3 Results  
### Phase-1: Relationships between 3D-Biopltting Parameters, Strand Width, and Cell Proliferation  
ANOVA results and the post hoc test show that extrusion pressure, nozzle speed, and their interaction had a statistically significant effect (\(p<0.001\)) on the strand width. The strand widths (mean \(\pm\) standard deviation) for the 16 combinations of extrusion pressure and nozzle speed are presented in Table S1 and the corresponding response surface plot is presented in Figure 3. A general trend of decrease in strand width with increasing nozzle speed and decreasing extrusion pressure was observed.  
A total of ten regression models ranging from squared to logarithmic were fitted to the data, and the model in Equation (2) provided the best R-squared value of 0.9046. In Equation (2), extrusion pressure is given in N/mm\({}^{2}\), nozzle speed in mm/s, and the strand width is estimated in \(\upmu\)m. From a validation perspective, the difference between the strand width estimate from this model (428.02 \(\upmu\)m) and the average experimental strand width (412.34 \(\upmu\)m) was 3.8%, which indicates good model fidelity.  
\[\begin{split} Strand\;width=368.17+132.70*\textit{ extrusion\;pressure}\;-\;368.45*\\ Log(nozzle\;speed)-798.53*[(\textit{\; extrusion\;pressure}\;-\;0.44)*\\ Log(nozzle\;speed)]\end{split} \tag{2}\]  
Results of % aB reduction for the 3 DB1 and 3 DB2 scaffold designs are presented in Figure 4a. The % aB reduction of both designs increased over time in culture, signifying an increase in cell proliferation. Overall, the % aB reduction for the 3 DB2 scaffolds was higher than that of the 3 DB1  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Model Type** & **Static Structure** \\ \hline
**Material category** & Isotropic elasticity \\
**Density (g/mm\({}^{3}\))** & \(3.16\times 10^{-4}\) \\
**Elastic modulus (N/mm\({}^{2}\))** & 58.14 \\
**Poisson’s ratio** & 0.3 \\
**Yield Strength (N/mm\({}^{2}\))** & 12.60 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Finite element (FE) model parameters.  
scaffolds. Results from the two-way ANOVA show that both the scaffold design and the days in culture had a significant effect on % aB reduction (\(p<0.05\)). [PERSON]'s HSD post hoc results show that the differences in % aB reduction between scaffold designs (pairwise comparisons) were significant on days 1, 3, and 5, but not on day 7. The Live/Dead(r) images show that the viable cells (green dots) adhered to the strands of both scaffold designs (Figure 4b,c). Dead cells, which would have manifested as red dots, were not observed, indicating cell viability approximating 100% in both designs.  
Figure 4: (a) % aB reduction of 3 DB1 and 3 DB2 scaffolds over 7 days. Error bars denote standard deviation (n = 3). (**b,c**) Representative live/dead image of 3 DB1 and 3 DB2 scaffolds, respectively, seeded with \(2\times 10^{6}\) NIH/3T3 cells on day 7. Live cells that attached to the strands (darker regions) are stained green (dots). The square regions irradiating green fluorescence in between the strands are empty pores.  
Figure 3: A Response surface plot of strand width (\(\upmu\)m) for combinations of different levels of extrusion pressure and nozzle speed.