Comparative Effects of Fine and Conventional Shot Peening on Surface Morphology, Topography, Wettability, and Antibacte-Rial Activity of Biomedical Ti6Al4V Alloy

Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising surface modification method. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade Ti6Al4V alloy. Peening was conducted using a custom-built, fully automated system, employing fine (100–200 µm) and coarse (700–1000 µm) shots using well-controlled sets of parameters. Both treatments introduced severe plastic deformation on the surface, resulting in increased roughness. Conventionally shot-peened samples exhibited deeper and wider dimples compared to finely peened ones. Surface wettability shifted from hydrophilic (contact angle: 4.1°, untreated) to hydrophobic, reaching contact angles of 91.13° and 99.76° for fine and conventional shot peening, respectively. Despite these topographical changes, both treatments preserved the intrinsic antibacterial activity of the alloy. Quantitative assays revealed high bacterial reduction rates after 6 hours of incubation: 99.58% (E. coli) and 92.54% (S. aureus) for fine shot peening, and 98.98% (E. coli) and 99.2% (S. aureus) for conventional shot peening. Both methods were effective in modifying the surface without compromising antibacterial performance. However, fine shot peening provided a smoother and more uniform surface topography, and thus potentially offers better control over bacterial adhesion and surface–cell interactions in biomedical applications.