Effect of laser surface modification on the tensile properties of ultra-thin titanium sheet

Abstract

Laser scanning irradiation (LSI) was a promising method to improve the surface hemo-compatibility of vascular stent (VS). This paper firstly studied the effect of LSI on the tensile properties of ultra-thin Ti sheet, the thickness of which was close to that of VS’s wall. Meanwhile, the influence of plastic deformation on the hydrophilicity of LSI sheets and the hydrophobicity of the ones modified with fluorosilane was evaluated. The results indicated that the tensile properties of Ti sheets gradually declined with increasing laser fluence (Fp) and decreasing scanning speed (v). As using laser gentle ablation (LGA) with Fp = 1.1 ∼ 2.9 J/cm2, the declination degree of tensile properties was relative slight, but it was obviously sharper as using laser strong ablation (LSA) with Fp = 4.0 ∼ 6.6 J/cm2. In addition, the tensile and yield strengths of LSA samples using v = 42 mm/s were much smaller than those using higher v of 126 ∼ 630 mm/s, owning to the much larger laser-ablated depth in the surfaces. All of the LSA surfaces exhibited superhydrophilicity, and after fluorination they rapidly turned to be superhydrophobic with low adhesion to water. Interestingly, plastic deformation within the tensile fracture point slightly improved the super-hydrophilicity or superhydrophobicity of these LSA surfaces rather than destroyed it. Therefore, LSA with v = 126 ∼ 630 mm/s was more suitable to be applied in the stent, which could not only obtain super-hydrophilicity/hydrophobic surfaces with hierarchical microtextures but just slightly affect the stent’s tensile properties.