Fabrication of Superhydrophobic Biomimetic Micro/Nano Surfaces on Titanium Alloys

Abstract

Bionic micro-nano structures are commonly used to modulate the wettability of material surfaces, thereby creating various hydrophilic and hydrophobic surfaces. In this study, a femtosecond laser was utilised to fabricate biomimetic rose petal (BRP) micro-nano cone array structures on the surface of Ti6Al4V (TC4) alloy, with a base radius of approximately 20 µm and heights of approximately 20 µm, 25 µm and 30 µm, respectively. Without fluorosilane modification, using a scanning speed of 70 mm/s, a line spacing of 0.003 mm, a power of 20 W, an output frequency of 100 kHz, a jump speed of 1000mm/s, and 80 scanning passes, a bio-inspired rose petal structure with a base radius of approximately 20 μm and a height of approximately 30 μm was fabricated. The surface contact angle was 0°, exhibiting superhydrophilicity; Following fluorosilane modification, the contact angle reached 152±0.32°, achieving a transition from superhydrophilicity to superhydrophobicity. Compared to chemically modified polished TC4 (contact angle 103±0.37°), the performance was significantly enhanced. The micro-nano structures provide mechanical stability and cavitation trapping capabilities, whilst surface roughness amplifies hydrophilicity; the silanisation treatment imparts thermodynamically low surface energy chemical properties. This system follows the Cassie-Baxter model, with water droplets suspended at the tips of the micro-nano structures, thereby achieving high contact angles and low adhesion.