In this work, we have used a nanosecond pulsed fiber laser to modify the wettability characteristics of AISI 430 steel. For this, various surface morphologies were created on the samples by laser irradiation with different overlapping and intensity parameters. Immediately upon laser treatment, all the structured samples acquired either hydrophilic or superhydrophilic wetting angles. All the samples were also analyzed with XRD. Then, laser-treated samples were kept in ambient air and/or low-temperature annealing was applied to reach hydrophobic surface properties. Interestingly, these surfaces returned back practically to their initial wetting state by cleaning in an ultrasonic bath. The obtained results are analyzed based on the existing wettability models.

The paper investigates how the surface relief of an implant affects cell behavior. Currently, most implant manufacturers claim the key impact biocompatibility factor to be surface micro-roughness. We suppose that the interaction between cells and implants also depends on such relief peculiarities as continuous or discontinuous topography, subcellular distance between peaks and presence of porous oxide layer. We have developed the laser processing conditions that provide three different reliefs: «open grooves», «grid» and «close grooves». Along with the micro-roughness characteristics the reliefs differ with their deepness and period of grooves. The surface composition analysis results have shown a sandwich structure consisting of Ti → TiO → Ti 2 O 3 Nx → TiO 2 (anatase) → TiO 2 (rutile). The wettability study has demonstrated superhydrophilicity (CA is 0 • ) for all reliefs. The quantitative and qualitative analysis of hMSCs proliferation and osteogenic differentiation was performed for 20 days. In vitro study has revealed the topography affects the spatial orientation of cells. The shape and size of the cell nuclei vary with different topographies. We have found continuous «open grooves» structures with the subcellular to cellular period are beneficial for cells' life-sustaining activity. Discontinuous «grid» structures with individual slots might not provide cells with mobility with the least external mechanical effect compared to «open grooves».

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