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Fabrication of four-level hierarchical topographies through the combination of LIPSS and direct laser interference pattering on near-beta titanium alloy
Complex repetitive periodic surface patterns were produced on a near-beta Ti-13Nb-13Zr alloy, using two-beam Direct Laser Interference Patterning (DLIP) employing a picosecond-pulsed laser source with wavelengths of 355 nm, 532 nm and 1064 nm. Different types of Laser-induced periodic surface structures (LIPSS) are produced, including low and high spatial frequency LIPSS, which are observed frequently on top of the line-like DLIP microstructures, as well as quasi-periodic microstructures with periods greater than the laser wavelength. The feature size of the fabricated LIPSS features could be tuned as function of the utilized laser process parameters.
Fabrication of multifunctional titanium surfaces by producing hierarchical surface patterns using laser based ablation methods
Textured implant surfaces with micrometer and sub-micrometer features can improve contact properties like cell adhesion and bacteria repellency. A critical point of these surfaces is their mechanical stability during implantation. Therefore, strategies capable to provide both biocompatibility for an improved implant healing and resistance to wear for protecting the functional surface are required. In this work, laser-based fabrication methods have been used to produce hierarchical patterns on titanium surfaces. Using Direct Laser Writing with a nanosecond pulsed laser, crater-like structures with a separation distance of 50 µm are produced on unpolished titanium surfaces. Directly on this texture, a hole-like pattern with 5 µm spatial period is generated using Direct Laser Interference Patterning with picosecond pulses. While the smaller features should reduce the bacterial adhesion, the larger geometry was designed to protect the smaller features from wear. On the multifunctional surface, the adherence of E. Coli bacteria is reduced by 30% compared to the untreated reference. In addition, wear test performed on the multiple-scale patterns demonstrated the possibility to protect the smaller features by the larger craters. Also, the influence of the laser treatment on the growth of a titanium oxide layer was evaluated using Energy Dispersive X-Ray Spectroscopy analysis. © 2019, The Author(s).