Easily creating slant microwall arrays by tailoring melt redistribution for directional liquid transportation

Abstract

Driving directional liquid transportation on structured surfaces has garnered significant attention. Laser texturing technology is favored for its efficiency and flexibility in creating functional surfaces. However, existing laser texturing processes often struggle to form the complex structures required for customized functional surfaces. In this study, we propose a novel strategy called vertically incident high-frequency pulsed laser tailored melt redistribution (viHPLTMR) to rapidly fabricate slant microwall arrays. This strategy employs nanosecond (ns) pulsed laser direct writing (DLW) with repeated line-by-line unidirectional scanning to control the flow patterns of the melt microfluidics. Specifically, the redistribution direction of melt microfluidics aligns with the advancing direction of the laser and is regulated by thermal effects from multi-pulse and periodic energy input. Proper selection of machining parameters allows for the adjustment of microstructure unit sizes and the transformation of microwall slant angles from 34° to 65°. Additionally, based on the multi-process analysis of microstructure characterization, a mechanism model of melt redistribution driven by high-frequency pulsed laser is established. This model reveals the formation process of array structures and the reasons behind their regular behavior. It was found that the constructed surface exhibits excellent superhydrophobicity and anisotropy, with droplets (6.4 μL) achieving a maximum horizontal bounce distance of 1.92 mm and up to 22 consecutive jumps, demonstrating significantly favorable long-distance directional liquid transmission ability. Unlike traditional heterogeneous gradient surfaces, these structured surfaces are free from regional limitations, offering greater flexibility and higher transmission speeds (10.4 mm/s). Furthermore, the viHPLTMR strategy can similarly control melt microfluidic motion and surface wetting performance on different metallic materials such as titanium alloy, stainless steel, magnesium alloy, and aluminum alloy, offering the advantages of low cost, high flexibility, and suitability for large-scale manufacturing.