Periodically oriented superhydrophobic microstructures prepared by laser ablation-chemical etching process for drag reduction

[Display omitted] •The factors for the formation and scales of microstructures were investigated.•The rebound coefficient of droplet on the achieved surface reached 82.85%.•The sample prepared by LACE has excellent drag reduction performance. Superhydrophobic surface gives prominence to its application potential in the field of anti-adhesion and drag reduction in the microchannels, because of its low adhesion and high repulsion to water. In the paper, nanosecond pulse laser ablation-chemical etching (LACE) process is proposed to prepare patterned superhydrophobic surface with the microstructures which are orientation-controllable, period-adjustable and height-manageable on the 316L stainless steel. It is found that the laser scanning speed is the prerequisite for the formation of microstructures, the average laser power and laser scanning interval are important factors affecting the period and height of microstructures. The rebound coefficient of water droplets can reach 82.85% on the superhydrophobic surface with a contact angle of 154.7°(±0.6°), which indicates that the achieved surface has exceptional repellency to water. The drag reduction test experiments demonstrate that it can effectively reduce the flow resistance in the microchannels without drag reducing agents, and the maximum drag reduction rate can reach 29.83%. The work demonstrates that the LACE process, preparing superhydrophobic surfaces with the microstructures and manipulating its structural parameters with multi-dimension, can be reliably applied to drag reduction and water repellency fields.