## 2 Materials and Methods
### Calibration of MEW Device's Parameters
#### 2.4.1 Non-Medical-Grade PCL Pellets  
Temperature was the first parameter evaluated while keeping the other parameters constant. Figure 3 presents the optical microscopy images used to measure the fiber diameter after printing, with measurements taken at multiple points on each mesh to ensure accuracy. The images show both the meshes produced with optimal parameters (Figure 3A,B) and those with inadequate printing parameters, which exhibit imperfections (Figure 3C-E). Temperatures of 160 \({}^{\circ}\)C and 180 \({}^{\circ}\)C were excluded due to printing instabilities, which resulted in irregular or inconsistent material flow from the printer nozzle during the 3D printing process (Figure 3C). At temperatures of 200 \({}^{\circ}\)C and 220 \({}^{\circ}\)C, the filaments were printed continuously. However, at 200 \({}^{\circ}\)C, the melt exhibited inadequate viscosity, making it unsuitable for the process. The next parameter analyzed was translational speed. Speeds of 300 mm/min and 2400 mm/min were excluded due to the occurrence of filament winding and curling (Figure 3E). A speed of 1000 mm/min was selected as it provided greater stability and prevented winding or discontinuities in the filaments. \begin{table}
\begin{tabular}{l c} \hline Temperature (\({}^{\circ}\)C) & 160; 180; 200; 220 \\ \hline Trans Speed (mm/min) & 300; 1000; 1700; 2400 \\ \hline Volt (kV) & 4.0; 6.0; 8.0; 10.0 \\ \hline Dist (mm) & 1.0; 1.5; 2.0; 2.5 \\ \hline \end{tabular} Note: Dist: nozzle/collector distance (mm); Temp: temperature (\({}^{\circ}\)C); Trans Speed: translational speed (mm/min); Volt: voltage (kv).  
\end{table} 
Table 1: Range of parameters tested, with both non-medical-grade and medical-grade PCL. Regarding voltage, the 6 kV setting was chosen, as it demonstrated stability without the issues observed at other voltages. Variations in voltage resulted in changes to the filament diameter (Figure 3D). The distance between the nozzle and collector was also assessed. The optimal results were obtained with a 2.0 mm distance, which showed no signs of filament elongation or other instabilities. Thus, the final parameters selected for non-medical-grade PCL pellets were (1) temperature--200 \({}^{\circ}\)C; (2) translational speed--1000 mm/min; (3) voltage--6.0 kV; and (4) distance--2.0 mm (Figure 3A,B). It is important to note that MEW printing involves not only staying within specific parameter limits but also finding the optimal combination of these parameters. After calibrating the parameters for non-medical-grade PCL, three meshes with filament diameters of 80 \(\upmu\)m, 160 \(\upmu\)m, and 240 \(\upmu\)m were printed. The diameters were measured using a microscope. The aim of these experiments was to calculate the error between the calculated diameter using Equation (1) and the experimental results to make necessary final adjustments. Table 2 presents the results from the diameter analysis for each print. The diameter values shown are averages calculated from measurements taken at three different points on each printed mesh. After evaluating the diameter, it was confirmed that the extrusion value needed to be adjusted for the filament extruder due to a systematic error of approximately 33%. As a \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Nominal Mesh** & **First Print** & **Second Print** & **Third Print** & **Mean Diam** & **Error (\%)** & **Mean Error (\%)** \\ \hline
240 \(\upmu\)m & 160.35 \(\upmu\)m & 161.83 \(\upmu\)m & 160.35 \(\upmu\)m & 160.84 \(\upmu\)m & 32.98\% & \\ \hline
160 \(\upmu\)m & 107.09 \(\upmu\)m & 106.45 \(\upmu\)m & 107.69 \(\upmu\)m & 107.08 \(\upmu\)m & 33.08\% & \\ \hline
80 \(\upmu\)m & 53.94 \(\upmu\)m & 53.20 \(\upmu\)m & 53.42 \(\upmu\)m & 53.52 \(\upmu\)m & 33.10\% & \\ \hline \hline \end{tabular} Note: Mean Diam: mean diameter (\(\upmu\)m).  
\end{table} 
Table 2: Evaluation of non-medical-grade PCL filament diameters.