OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 4 2024 including materials for medical purposes (biomaterials) [1, 6–10]. The main purpose of surface treatment of metallic biomaterials is to obtain a modifi ed layer with specifi c properties on the material surface. Such surface characteristics as wettability, surface energy, roughness, phase and chemical composition have a signifi cant impact on the biocompatibility of materials in a physiological environment. In this case, both the corrosion properties and the ability to integrate biomaterials into living biological tissues largely depend on the wettability of these materials with biological fl uids, aqueous solutions of salts and acids [4, 6, 7, 9, 11, 12]. In terms of interaction with biological fl uids, cells and tissues, a hydrophilic surface is more preferable than a hydrophobic one. Unlike conventional materials, the surface of implants with increased hydrophilicity provides higher rates of osseointegration, i.e. interaction of biomaterial with bone tissue without the participation of connective tissue [13]. The ability of lasers to change the surface characteristics of material and, consequently, its interaction with the environment has attracted great interest among researchers in using this unique feature to improve the material behavior in biological environments [9, 11, 12, 14–17]. The advantage of using laser radiation for modifying the surface of various materials is that laser treatment is an environmentally friendly, noncontact and relatively fast method, and this method of treatment is characterized by high accuracy and the possibility of local infl uence. By adjusting the parameters of laser treatment, it is possible to selectively change the surface of the material without aff ecting its internal structure and volumetric properties. Nowadays, lasers are increasingly used as a tool for modifying the surface of various metallic materials and devices which are used as biomedical materials in cardiology, orthopedics and dentistry and other areas [11, 18–20]. The works [1, 5, 9, 11, 14, 18–22] note that lasers are mainly used to modify the surface of metal implants in order to improve osseointegration, corrosion resistance and hydrophilicity. Metallic biomaterials based on titanium and its alloys, as well as stainless steel, are used in the manufacture of artifi cial heart valves, pacemakers, stents for blood vessels, bone and joint endoprostheses (shoulder, knee, hip, elbow), for auricles reconstruction, in facial surgery, and also as dental implants. These biomaterials prevail over other classes of biomaterials due to the synergistic combination of excellent mechanical properties, corrosion resistance and wear resistance, as well as long-term biocompatibility [12, 14, 19, 20, 23, 24]. Recently, controlled laser treatment has been actively studied to change the topography, morphology, and physicochemical properties of the surface of biomaterials, including with the aim of reducing bacterial adhesion on the surface of implants and, thus, tuning its biological and other surface properties [11, 16, 17, 20, 22, 25]. In vitro and in vivo studies have been conducted to estimate the eff ect of laser treatment on adhesion, cell growth and proliferation, wettability, surface hardness, mechanical properties, surface morphology, antibacterial properties, and biofi lm formation on the surface of implants [13, 15–17, 20, 23, 25, 26]. It should be noted that basically all studies on laser treatment on materials surface aimed at changing the morphology, topography and properties of the materials surface were carried out using radiation with a wavelength of λ = 1,064 nm or λ = 532 nm with high values of energy density or power [10, 15, 17, 25, 27]. Works on the study of the eff ect of ultraviolet (UV) laser radiation (λ < 400 nm) on the surface of materials are not many [20, 28, 29]. However, despite numerous recommendations on using laser surface treatment, there is still lack of systematic and detailed studies of the eff ect of laser radiation parameters on the structural-phase state and properties of the modifi ed surface of metallic materials. The purpose of this work is to study the hydrophilic behavior of the surface of TiNi alloy and stainless steel after UV laser treatment. The objective of this study is to conduct a comparative analysis of the contact angle, structure, topography, phase and chemical composition of the surface of TiNi and steel specimens before and after laser treatment with a change in the exposure duration. Materials and methods of investigation The experimental specimens in the form of plates with dimensions of 10×10×1.5 mm (length × width × thickness) made of an alloy based on titanium nickelide TiNi (TN-10), developed at the Research institute of
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