## 4 Conclusions  
Femtosecond pulsed laser irradiation was performed to embed silver nanoparticles in nanopores on YSZ, and its fundamental characteristics were investigated. The conclusions are summarized as follows. 1. Silver nanoparticles were successfully embedded in nanopores generated by irradiating a YSZ substrate with a femtosecond pulsed laser, by dropping a commercially available nano-silver dispersion into the pores and re-irradiating the laser. 2. By irradiating at the fluence in a limited range much lower than the ablation threshold, the polyvinylpyrrolidone (PVP) polymer dispersant remaining on the outer surface \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Substrate Material** & **Substrate Structure** & **Embedding Material** & **Embedding Method** & **Ref.** \\ \hline (a) & Cellulose nanofiber (CNP) & Nanofiber & Ag nanoparticle & High-pressure wet-type jet mill & [8] \\ (b) & Graphene oxide (GO) & Nanosheet & Ag nanoparticle & Laser ablation in GO suspension & [7] \\ (c) & Titanium & Polished flat surface & Ag nanoparticle & Deposition in silver nanoparticle solution & [49] \\ (d) & Fused silica & Nanopore arrays & Peptide & Adsorption & [10] \\ (e) & Yttria-stabilized zirconia (YSZ) & Nanopores & Ag nanoparticle & Laser irradiation & This study \\ \hline \end{tabular}
\end{table} 
Table 3: Material loading methods. of the nanopores was selectively decomposed and removed. On the other hand, increasing the fluence at low scanning speeds caused delamination of the YSZ substrate surface and the formation of laser-induced periodic surface structures. Laser fluence and scanning speed interacted to embed silver in the pores while maintaining the grain shape of the substrate surface. The best conditions in this study were laser fluence of 0.6 J/cm\({}^{2}\) and scanning speed of 200 mm/s, at which the silver implantation rate reached about 60%. 3. When the pulse width was increased, the substrate surface melted and a crack occurred due to the thermal effect. At the same time, not only the PVP but also silver was removed from both the surface and inside the pores, indicating that ultrashort pulses are suitable for maintaining the substrate surface morphology and silver loading. 4. The silver nanoparticles melted and agglomerated, forming large agglomerates inside the nanopores by laser irradiation while separated from the dispersant PVP. The silver was embedded to the bottom of the elongated pore, reaching a depth of approximately 600 nm from the surface. 5. The thermally induced tetragonal-to-monoclinic phase transformation was suppressed on the YSZ surface after embedding silver nanoparticles in the nanopore by using low laser fluence under the ablation threshold, indicating no thermal damage to the bulk. This study demonstrated the new approach to the functionalization of YSZ surfaces by implanting different materials in nanopores by the femtosecond pulsed laser process without causing severe thermal damage to the bulk. This technique enabled the local embedding of metal nanoparticles without causing significant thermal damage to the bulk. The method can be expected to be a cost-effective system, as it can be completed using only a low-power femtosecond pulsed laser system and requires a small amount of commercially available silver nanoparticles. In addition to the surface features of zirconia, such as biocompatibility, silver-loaded YSZ substrates are expected to have a synergistic effect due to the sustained antimicrobial effect of silver fixed in the surface nanopores. These findings not only deepen the scientific understanding of the ablation properties of the different materials on the substrate, but also provide the potential to expand new applications for zirconia by adding value through surface functionality such as antibacterial properties, biocompatibility, and nanomedicine delivery.