Time-dependent wetting behavior of the micro-textured stainless steel 316L using the mechanical indentation method

Abstract

The current work introduces a mechanical indentation method to develop and characterize the pyramid-shaped micro-texturing in a square array on biomedical grade SS 316L. The surface morphology, topography, and roughness profiles of the pyramid-shaped micro-textured surfaces are characterized using a field emission scanning electron microscopy, three-dimensional (3D) optical profilometer, and atomic force microscopic (AFM) analysis. The field emission scanning electron microscopy results showed that micro-textures are formed in a periodic manner at different center distances within 2% of error. The AFM 3D image shows the bulging effect near the corners of the pyramid textures due to the application of applied load. Further, the S_a values of the textured samples are found as 1.223, 0.52, and 0.271 µm for the center distance of 150, 250, and 350 µm, respectively, and come under the micro-roughness (S_a > 1–10 µm) and nano-roughness (S_a< 1 µm) scale range. Further, the surface functionality was analyzed in terms of Young's contact angle. The textured surface presents hydrophilic wetting behavior with a contact angle of 42.8°, compared to the untextured part (97.4°) for deionized water. Moreover, with PBS, the textured sample show presents a minimum contact angle, that is, 22.7°, compared to the untextured part (81.1°), which presents a high affinity for simulated body fluid. The results indicate that an increase in surface roughness makes the hydrophilic surface more hydrophilic, supporting the Wenzel statement. Therefore, the mechanical indentation technique can be a promising method for fabricating micro-textured surfaces for implant materials.