Direction dependent dynamic wetting of semi-hemispherical end micro-groove textured Ti-6Al-4V surface

Abstract

The present work introduces the single step facile fabrication of semi-hemispherical end micro-grooved textures on Ti-6Al-4V flat surfaces using ball-end micromilling and their impact on surface morphology and direction dependent dynamic wetting of ultrapure deionized water nanodroplet. Directional dynamic wetting was analyzed from both parallel and perpendicular viewing directions of the micro-grooved textures using measurement of the dynamic contact angles. It was further utilized to predict Young's equilibrium contact angle which was also compared with Wenzel and Cassie-Baxter wetting models. Predicted values of Young's equilibrium contact angle in both the directions were also correlated with the geometrical parameters of the fabricated micro-grooved textures. The semi-hemispherical end micro-groove geometry enhances the surface wetting whereas, micro-grooved textures confine the droplet spreading along its length leading to directional wetting. The nanodroplet stretches along micro-grooves and distorted in transverse direction leading to comparatively lower contact angle in perpendicular viewing direction to that of parallel viewing direction. Results reveal that there exists a strong anisotropic wetting nature for the low pitch and high depth of micro-grooved texture. Anisotropic wetting almost disappears for 300 μm pitch due to minimum contact between the nanodroplet and micro-grooved textures where the dominance of un-textured ridge portion is significant.