Laser surface structuring on β titanium alloy for orthopaedics : effects of pulse duration and wavelength

This study investigates the effects of different types of laser on the surface of a Beta Titanium for biomedical implants application. Picosecond fiber laser, nanosecond fiber laser and nanosecond Nd:YAG were compared to produce different types of surfaces and enhance wetting proprieties for biological applications. Laser processing was carried out in air environment and direct writing method is explored as a potential technique to enhance the wettability of orthopaedic implants. Using the DOE approach, the following parameters have been investigated: pulse energy, scan speed, pulse width, wavelength and pitch distance. Surface topology, surface roughness, wettability, phase crystallinity and chemical composition were characterized using SEM, 3D confocal microscope, goniometer, X-ray diffractometer and X-ray photoelectron spectroscopy. In order to produce hydrophilic and super-hydrophilic surfaces for improving osseointegration between the prosthesis and the bones, the analysis of the laser surface structuring was part of this work. A series of regular features with dimension of the order of tens of microns are generated on the surface treated with the nanosecond lasers. The picosecond laser generated laser-induced periodic surface structures (LIPSS). The superficial structures obtained with the different lasers were compared one against each other, and the relative peculiarities have been highlighted. Furthermore, the lasers were compared also in terms of productivity and possible tangible future applications. It is shown that a laser treatment in air enhances the surface roughness which in turn promotes the hydrophilicity or hydrophobicity. The chemical composition, crystalline phase, shape and the distribution of the created surface structures are also effective in this regard.