Enhanced Mechanical and Biological Performance of an Extremely Fine Nanograined 316L Stainless Steel Cell–Substrate Interface Fabricated by Ultrasonic Shot Peening

An extremely fine nanograined (NG) rough surface with the average grain size of 10 nm was successfully fabricated on 316L stainless steel (316L SS), which is a commonly used bioimplant metallic materials, via a simple physical therapy, namely, ultrasonic shot peening (USP). This extremely fine NG rough surface was proposed as the cell–substrate interface to enhance the mechanical and biological performance of 316L SS in orthopedic applications. Nanoindentation and micropillar compression tests indicated the significant improvement of the nanohardness and yield strength of the developed NG-316L SS, respectively, and the “in vitro” studies demonstrated that the developed extremely fine NG-316L SS rough surface could significantly enhance the attachment of the human osteoblast cells (Saos-2) compared with the as-received coarse-grained 316L SS surface. The observed mechanical and biological enhancement of the extremely fine NG-316L SS surface can be attributed to the ultrahigh-density nanosized grain boundar...