# Phase Transition and Controlled Zirconia Implant Patterning Using Laser-Induced Shockwaves
## 3 Results
### Laser Pattern Imprinting on Zirconia  
The sintered properties of zirconia, particularly its high compressive strength, inherent hardness, and brittleness, create substantial obstacles to deformation under pressure. These attributes make patterning attempts exceedingly difficult, as the material's resistance to mechanical alteration often exceeds the capabilities of conventional patterning techniques. Unlike metals that deform plastically, zirconia tends to fracture because of its Hugoniot elastic limit (HEL) of 20-25 GPa [43]. Recognizing tetragonal zirconia's hardness, we tried green body and pre-sintered zirconia, seeking a balance between malleability for patterning and robustness to prevent fracturing. The two critical factors to consider are pattern retention and pattern precision. Sintered zirconia offers the highest pattern retention, whilst leaving much to be desired for pattern precision. The opposite is true for green body zirconia. Thus, finding a middle ground is an ideal case scenario. During our trials, the green body zirconia produced the best results, as the two-stage sintering improved pattern retention. Thus, we found green body zirconia to be the primary candidate for patterning. Figure 2 shows SEM images illustrating the square grid pattern achieved on a zirconia pellet surface. Initially smooth and unblemished, the zirconia surface was patterned using  
Figure 1: XRD pattern of zirconia. Sintered (red), pre-sintered (green), and green body (blue) ZrO\({}_{2}\) XRD profiles. the first method, which used graphite as a sacrificial layer. We administered a 1.2 J/cm\({}^{2}\) laser shot for 2 s, aiming for a uniform and reproducible pattern with high fidelity. The results show a clean imprint of the grid template. Elemental analysis of the grid square and pitch revealed similar compositions, containing zirconia and oxygen, as expected. The use of graphite in this method makes it unsuitable for sensitive fields such as medical implants. Nevertheless, this technique has shown promise in patterning on copper and titanium plates, where the precision and cleanliness of the imprint are less critical. The alternative approach uses aluminum as the ablative layer, making it more suitable for sensitive applications. Aluminum as a sacrificial layer facilitates a clearer, more precise imprint on the surface, without leaving any trace (see Figure 3). SEM and AFM images of zirconia patterned via laser template imprinting reveal a highly precise and well-defined pattern. The SEM images show the uniformity and clarity of the imprinted patterns, highlighting the effectiveness of the proposed technique. The AFM images further support these findings, demonstrating excellent imprinting quality with clear and distinct features (see Figure 4). Notably, the depth profile observed in the AFM images is significantly deeper than that typically achievable with other laser-patterning methods, such as femtosecond pulsed laser irradiation and direct laser interference patterning (DLIP) [44; 45]. These methods, while effective in creating precise microstructures and nanoscale periodic surface structures, often do not achieve the same depth and intricacy as nanosecond laser template imprinting. This enhanced depth profile is particularly important for zirconia implants because it promotes better osseointe  
Figure 3: Zirconia surface patterned via the “aluminum method”. First row: Cu (400) square mesh TEM template at F = 2 J/cm\({}^{2}\), t = 1 s. Second row: Cu (400) hexagonal mesh grid TEM template at F = 2 J/cm\({}^{2}\), t = 1 s.  
Figure 2: ZrO\({}_{2}\) patterned via the “graphite method”. Cu (400) mesh TEM grid template at F = 1 J/cm\({}^{2}\), t = 2 s.  
surface area, which allows for stronger and more stable integration with the bone [46; 47]. In addition, deeper patterns improve mechanical stability by providing better mechanical interlocking, reducing the risk of implant loosening or failure. They also help distribute mechanical stress more evenly, reducing the likelihood of fractures.