Improving Surface Hydrophobicity by Microrolling Based Texturing

Abstract

A twopass microrollingbased texturing (خ¼RT) process was utilized to improve the hydrophobicity of aluminum surfaces. Square micropillars were fabricated on aluminum sheets by two mutually orthogonal forming passes by a roller pretextured with microgrooves. Subsequently, the droplet contact angle was measured to evaluate the hydrophobicity of the surface. Results show that surfaces with خ¼RTimprinted textures have higher contact angles than nontextured surfaces indicating improved hydrophobicity. Furthermore, the process has led to the creation of hierarchical valleylike features on top of each of the micropillars caused by the pileup effect during the forming process. It was hypothesized that such hierarchical features positively contribute to the improved hydrophobicity of the surface. This hypothesis was validated by testing surfaces with a similar hierarchical textured pattern produced by laserinduced plasma micromachining (LIPMM). The effects of various aspects of texture geometry including surface areatovolume ratio and groove aspect ratio on the surface contact angle and the anisotropy of the contact angles were investigated.