Evaluation of hydrophilicity and surface morphology of nanosecond-pulsed laser-engineered surface textures on stainless steel, cobalt-chromium, and titanium alloys.

Abstract

The need to improve biocompatibility and to ensure successful integration of biologically compatible metals or bio-metals with biological tissues has resulted in the development and creation of engineered surfaces as biomaterials for use as implants and bio-medical devices. Through laser surface texturing, precise control over surface micro-topography, and microstructure pattern can be achieved, that optimize and enhance cellular adhesion, growth and differentiation-key factors that prevent implant rejection and improve device functionality and performance. This study investigates nanosecond-pulsed, laser-engineered surface texturing on stainless steel, titanium, and cobalt-chromium alloys, particularly for use in biocompatible implants. Coupons of each material were textured using uniform laser parameters, resulting in engineered surfaces with distinct and defined peaks and valleys, creating micro-topographies influenced by the Gaussian profile of the laser, as analyzed via SEM (scanning electron microscopy) and optical profilometry. Surface analysis showed that engineered textures on stainless steel demonstrate high uniformity with surface roughness measured to be 0.897 μm (R_a), facilitating better cellular adhesion, an essential feature for implant integration. This was confirmed via water contact angle test that showed a moderately hydrophilic surface showing consistent behavior (mean Water Contact Angle (WCA)) close to 71.1°, variance 0.17). Energy dispersive X-ray spectroscopy (EDX) indicated minimal surface oxidation across all samples, consistent with processing under an inert gas environment. Additionally, a computational model was created to verify and validate the "experimental surface-textured" profiles of each of the materials within a 5% margin, confirming the accuracy and reproducibility of the laser-processing technique. The uniform micro-scale surface topography and preserved surface chemistry of SS316L show that it promotes cell-adhesion and enhanced potential for biomedical implant applications compared to Co-Cr and Ti-6Al-4V.