## 4 Discussion
A smaller standard deviation in sheet resistance across plated samples suggests that BSA pretreatment not only enabled more uniform metal deposition but also ensured consistent outcomes across different samples. Conversely, a larger standard deviation implies that the plating process was unstable, resulting in sample-to-sample variability in coating quality. Therefore, the magnitude of the standard deviation serves as a quantitative indicator of the uniformity and reproducibility of the electroless plating process. The results presented herein quantitatively demonstrate that BSA pretreatment significantly enhances both of these aspects. As plating proceeded under stable conditions, the sheet resistance initially decreased and reached a minimum value as a continuous conductive Cu network was formed (Figure 2f). However, when the plating time exceeded the optimal point, excessive Cu deposition occurred, leading to delamination and subsequent increases in resistance and structural degradation in both groups. In the ENMH group, a sharp rise in both resistance and standard deviation was observed after 12 min, corresponding to the onset of Cu layer delamination. In contrast, the ENMH(-BSA step) group exhibited a similar trend after 30 min, likely due to lower plating efficiency and a delayed transition to a conductive state. These results suggest that excessive plating time can compromise mechanical and electrical stability due to overgrowth of the metal layer, indicating the existence of an optimal plating duration. In particular, the delayed formation of a continuous Cu network in the ENMH(-BSA step) group is attributed to the absence of BSA pretreatment, which results in reduced plating efficiency and prolonged time to achieve conductivity. This finding supports the notion that over-deposition can weaken structural integrity and further demonstrates that BSA pretreatment facilitates rapid and uniform formation of the Cu network in the early plating stage, thereby contributing to lower final resistance. A similar trend was observed in interfacial adhesion performance. In the 90\({}^{\circ}\) T-peel test, the ENMH samples exhibited a relatively high average peel strength in the range of 0.073-0.096 N/mm (Figure 3b), with minimal visible Cu residue on the tape surface after peeling (Figures 3f and S1), indicating strong adhesion between the Cu layer and the nanofiber substrate. In contrast, the ENMH(-BSA step) samples showed lower peel strength and significant Cu residue on the peeled tape, suggesting weaker interfacial bonding. To further quantify adhesion characteristics, the Cu residue was analyzed using the tape area fraction metric, calculated as (residual Cu area/total observed tape area) \(\times\) 100. This image-based analysis (Figure 3g) provides a numerical indicator of delamination behavior across peeling cycles. After five peel cycles, the tape area fraction for ENMH remained low at 25.9%, whereas the ENMH(-BSA step) reached 64.6%, representing more than a 2.5-fold increase. This result highlights the positive impact of BSA pretreatment on interfacial adhesion stability under repeated mechanical stress. In terms of electrical stability and mechanical durability, the sheet resistance of the ENMH increased from 2.542 \(\pm\) 0.135 \(\Omega\)/sq to 9.982 \(\pm\) 3.521 \(\Omega\)/sq after five peel cycles, representing an approximate 3.9-fold increase. In contrast, the ENMH(-BSA step) exhibited a dramatic increase from 124.300 \(\pm\) 71.240 \(\Omega\)/sq to 4781.520 \(\pm\) 2352.100 \(\Omega\)/sq over the same period, corresponding to a 38.5-fold rise (Figure 3h and Figure S4). When comparing the post-peel sheet resistance values directly, the ENMH(-BSA step) was nearly 479 times higher than the ENMH after five cycles, underscoring a critical loss in conductivity and mechanical robustness in the absence of BSA treatment. These results emphasize the essential role of BSA in maintaining interfacial integrity and mitigating fatigue-induced failure under repeated mechanical stress.