## 4 Discussion  
In this study, a BSA-assisted electroless Cu plating process was applied to a PVDF-HFP nanoweb to develop the ENMH. To enhance interfacial properties, a biomimetic BSA-based interfacial layer was introduced. Experimental results demonstrated that incorporation of the BSA treatment significantly improved the uniformity of the metal coating and the interfacial adhesion to the polymer substrate. These improvements enabled the fabrication of an ENMH with enhanced electrical performance, interfacial stability, and reliable thermal output. SEM and EDS analyses confirmed that the ENMH featured a dense, continuous Cu coating uniformly distributed throughout the nanofiber network (Figure 2a,a',c,c'). In contrast, the ENMH(-BSA step) showed non-uniform and discontinuous Cu deposition (Figure 2b,b',d,d'), indicating that the presence of BSA effectively promoted Pd ion dispersion and immobilization, leading to greater continuity and depth of the electroless Cu layer [20; 47]. Further analysis supports the conclusion that BSA also plays a pivotal role in reducing Pd precursors and facilitating the formation of Pd nanoparticles [20] (Figure 3c-e). The uniform Pd distribution suggests that BSA functions as both a mild reducing agent and a stabilizer, preventing nanoparticle aggregation during nucleation and growth [48]. Figure 5: Durability and practical performance evaluation of the ENMH. (**a**) Images of the ENMH before (0%) and after (100%) strain. Durability test under 100% tensile strain while maintaining a constant voltage of 1 V (one-time strain applied for 10 s at around 190 s). (**b**) Image of the sample under 120\({}^{\circ}\) bending deformation. Durability test under 120\({}^{\circ}\) bending with ENMH and ENMH(\(-\)BSA step) at an applied voltage of 0.6 V. Bending was applied at 5 s intervals. (**c**) Heating performance test of the ENMH integrated onto the knuckle of the index finger under repeated bending at an applied voltage of 0.6 V. Images show the finger before (1) and after (2) bending. (**d**) Heating performance test and infrared image of the ENMH integrated into the fabric. Heated under 0.4 V and maintained for 5 min. TEM revealed a distinct lattice spacing corresponding to the Pd(111) plane, and the SAED pattern exhibited ring structures, indicating polycrystalline characteristics with high local crystallinity [37]. This structural feature may be advantageous in future electrochemical or catalytic applications. In addition, EDS detection of sulfur supports the involvement of sulfur-containing amino acid residues, such as cysteine in BSA, in coordinating with Pd\({}^{2+}\) ions and contributing to their reduction [20]. Taken together, these findings highlight that the BSA-based interfacial layer not only initiates and stabilizes Pd nanoparticle formation but also enhances their colloidal stability. BSA thus functions as an active mediator in guiding Pd nanostructure synthesis rather than merely serving as a passive support [20,47]. The electrical properties of the samples clearly demonstrated the fundamental structural differences induced by BSA pretreatment (Figure 2e). The ENMH group exhibited a low sheet resistance of 1.895 \(\pm\) 0.931 \(\Omega\)/sq after 11 min of plating, indicating high conductivity and good process reproducibility. In contrast, the ENMH(-BSA step) group showed a much higher sheet resistance of 328.809 \(\pm\) 268.666 \(\Omega\)/sq, along with substantial variation across samples. This pronounced difference can be attributed to the role of BSA in the early stage of plating. BSA promotes more uniform nucleation and Pd\({}^{2+}\) ion dispersion, which leads to denser and more homogeneous Cu deposition. The large error bars observed in the BSA-free group do not result from random measurement noise but rather reflect the intrinsic instability in nucleation dynamics and film formation.