Study on Nanosecond Laser Fabrication of Superhydrophobic Surface on Aluminum Alloy and Thermal Bounce Behavior of Droplets

In recent years, fabrication of superhydrophobic surfaces on metallic materials has attracted increasing attention. In this study, 6061 aluminum alloy superhydropholic surface with spiral micron ridge structure is fabricated by using the nanosecond laser processing method. The contact and roll angles between the droplets and surfaces are measured, and combined with the lattice Boltzmann simulation method, the thermal bounce behavior of droplets on the spiral micron ridge structure is investigated. The results show that the etching depth of the sample decreases with the increase of scanning speed. The contact angle between the droplet and surface with the spiral micron ridge structure and no fluoridation is about 7°, indicating that the surface has super hydrophilicity; the contact angle between the droplet with spiral micron ridge structure and fluoridation is about 150°, indicating the surface has superhy drophobicity. The roll angles between the droplets and spiral micron ridge structures prepared at low and high scanning speeds are about (7±2)° and (33±1)° respectively. Different scanning speeds make the aluminum alloys have different adhesiveness. The droplets are more likely to undergo thermal bouncing on the surface having a larger etching depth because the vaporization of the droplet after contacting with the hot surface generates a greater upward pressure underneath the droplet, pushing the droplet to bounce continuously.