## 3 Results and Discussion
### Characterization of PCL/CNC Wet-Spun Filaments  
The thermogravimetric analysis (TGA) was conducted to assess the thermal stability and degradation behaviour of the PCL/CNC composite filaments compared to pure PCL \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Tensile** & **Maximum Stress** & **Breaking** & **Strain (\%)** & **Young’s** & \multirow{2}{*}{**R\({}^{2}\)**} \\  & **(MPa)** & **Deformation (\%)** & **Point (MPa)** & **Strain (\%)** & & **Modulus (GPa)** & \\ \hline F1 & 70.28 & 1130.36 & 69.86 & 1129.72 & 0.18 & 0.95 \\ \hline F2 & 131.86 & 773.28 & 129.12 & 786.00 & 0.19 & 0.92 \\ \hline F3 & 201.34 & 750.30 & 200.87 & 762.47 & 0.21 & 0.92 \\ \hline F4 & 80.01 & 957.29 & 79.26 & 858.04 & 0.17 & 0.96 \\ \hline F5 & 169.10 & 947.16 & 161.40 & 956.22 & 0.22 & 0.92 \\ \hline F6 & 277.65 & 904.40 & 272.68 & 913.21 & 0.27 & 0.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Maximum tension, maximum stress deformation, breaking point, strain, and Young’s modulus of the filaments obtained. and CNC, which is critical for determining their suitability for ACL tissue engineering applications. The ability of the scaffold to maintain structural integrity under physiological and sterilization conditions is vital for its potential use in biomedical applications. A higher degradation temperature indicates better thermal stability, which is advantageous during manufacturing, sterilization, and implantation. In this analysis, the samples were subjected to a controlled increase in temperature until they reached 600 \({}^{\circ}\)C, allowing for the observation of their respective degradation profiles. Figure 2a shows the TGA curves of the samples in question, highlighting the loss of mass as a function of the increase in temperature. Additionally, Figure 2b shows the first-order derivatives of the TGA curves (DTG), which allow a more precise assessment of the degradation stages. The TGA and DTG curves of PCL reveal that this polymer undergoes degradation in a single stage, occurring between 350 \({}^{\circ}\)C and 450 \({}^{\circ}\)C, resulting in a mass loss of approximately 96%. It is also worth noting that the maximum degradation temperature of PCL is reached at 411 \({}^{\circ}\)C, which is consistent with the literature [45]. In the case of CNC, degradation occurs between 250 \({}^{\circ}\)C and 380 \({}^{\circ}\)C, with a mass loss of approximately 90%, reaching the maximum degradation temperature at 308 \({}^{\circ}\)C. Regarding the 30% PCL/3% CNC filament, the TGA curve shows a major degradation process around 400 \({}^{\circ}\)C. The degradation of CNC at a lower temperature range (300-350 \({}^{\circ}\)C) introduces a secondary degradation peak in the PCL/CNC filaments, which confirms the successful incorporation of CNC into the polymer matrix [46]. The increased thermal stability of the PCL/CNC composite around 400 \({}^{\circ}\)C suggests improved interaction between PCL and CNC, which may contribute to enhanced mechanical properties observed in other tests. The TGA results demonstrate that the addition of CNC slightly alters the thermal degradation profile of PCL, potentially reinforcing the polymer matrix and enhancing its performance under mechanical stress, as observed in tensile testing. This supports the hypothesis that CNC contributes to the mechanical reinforcement of PCL for ACL repair applications. Field Emission Scanning Electron Microscopy (FESEM) was used to assess the surface morphology and cross-sectional structure of the PCL and PCL/CNC filaments. The analysis provided insights into the uniformity, surface texture, and integration of CNC within the polymer matrix. Figure 3a,b shows FESEM images of PCL and PCL/CNC filaments. FESEM images of pure PCL filament revealed a smooth homogeneous surface with uniform diameters, indicative of a well-controlled wet-spinning process. In contrast, the incorporation of CNC into the PCL matrix introduced notable changes in surface morphology.