Ultrafast laser texturing of Ti-6Al-4V surfaces for biomedical applications

Abstract

By controlling processing parameters such as the average fluence, number of laser pulses and beam polarization direction, different types of multiscale surface textures were produced on Ti-6Al-4V surfaces by ultrafast laser processing. The samples were textured in ambient atmosphere using an Yb: KYW chirped-pulse-regenerative amplification laser with a wavelength of 1030 nm and pulse duration of 500 fs. The wetting of simulated biological fluids as well as the human mesenchymal stem cells (hMSCs) behavior were assessed. Three types of textured surfaces were tested, consisting of: (i) Laser-Induced Periodic Surface Structures-LIPSS; (ii) nanopillars-like structures; and (iii) LIPSS overlapped to microcolumns. The laser textured surfaces present hydrophilic behavior and high affinity for HBSS (Hank’s balanced salt solution). Cell spreading and adhesion strength is reduced by the laser nanotextures as compared to a polished control surface. Cytoskeleton stretching and stress fibers were clearly observed on LIPSS while significant filopodia formation was verified on nanopillars. There was no cell proliferation on the laser nanotextured surfaces. Ultrafast laser texturing of Ti-6Al-4V surfaces is an efficient technique for increasing surface wettability, and is potentially useful as a technique to control the behavior of hMSCs by changing the cytoskeleton shape, FAPs distribution and area, and proliferation.