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

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 degrees(+/- 0.6 degrees), 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.

Automated summary

This paper proposes a nanosecond pulse laser ablation-chemical etching (LACE) process to prepare a patterned superhydrophobic surface on 316L stainless steel, which has controllable microstructures in terms of direction, period, and height. The experimental results indicate that the laser scanning speed is a prerequisite for the formation of microstructures, and the average laser power and scanning interval are important factors affecting the period and height of microstructures. The superhydrophobic surface achieves a rebound coefficient of 82.85% for water droplets with a contact angle of 154.7 degrees (+/- 0.6 degrees), demonstrating exceptional water repellency. Drag reduction tests show that it effectively reduces flow resistance in microchannels, with a maximum drag reduction rate of 29.83%. This work demonstrates the reliable application of the LACE process in drag reduction and water repellency, utilizing superhydrophobic surfaces with controllable microstructures and structural parameters.