Surface texture fabricated by ultrafast laser treatment for manipulating wettability and cell adhesion performance of Ti6Al4V

Inspired by natural microstructure on human bone surface, two kinds of well-defined surface texture were designed and fabricated on titanium alloy by ultrafast laser technology with high precision. The fabricated surface texture can achieve adjustable contact angles ranging from 27° to 147° with designed geometric parameters, following the contact angle model. It is observed that the surface morphology, elemental composition, and wettability can collectively influence the cell adhesion behavior. The cells exhibit a preference for hydrophilic environment and tend to adhere along specific orientation of the surface texture, forming spindle-like shapes. In addition, the low concentrations of Carbon (C), Nitrogen (N), and Oxygen (O) elemental composition at the bottom of the surface texture gaps, combined with effective anchoring protein attachment sites, can significantly promote the localization of cell nuclei, with which the direction of cell adhesion can be determined. Notably, isotropic structures enable cells to adhere over larger areas. What's more, the cell adhesion performance can be influenced by the difference in residual stress. This study revealed that the manipulation resolution of cell growth rate and growth direction through fabricated surface texture can reach 35 μm. This study is believed to benefit future orthopedic implant design and applications.