Large-area surface wettability patterning of metal alloys via a maskless laser-assisted functionalization method

An innovative laser-assisted functionalization (LAF) method is presented in this work to fabricate a superhydrophobic-superhydrophilic patterned surface on a large-area metal alloy with a high process throughput. The LAF method comprises four steps, including two laser processing steps and two surface chemistry modification steps. Two strategies are demonstrated to fabricate extreme wettability patterns on aluminum alloy without using protective masking. Strategy I fabricates contrasting topography and chemistry where superhydrophobic regions are nanostructured with fluorocarbon chemistry, and superhydrophilic regions contain microchannels with nitrile chemistry. Conversely, strategy II fabricates similar microchannel topography for both wettability regions with contrasting chemistry. Surface topography patterning, from low-roughness, isotropic, random nanostructured texture to highly structured texture, is achieved by adjusting the laser parameters during LAF. LAF constitutes the first known laser-based surface engineering method that decouples extreme wettability from surface topography. In addition, anti-reflection surface property, ranging from moderately reduced reflectivity of about 50% to ultralow reflectivity of less than 10%, is achieved using this process. The processing mechanism, surface chemistry, and surface topography are analyzed to demonstrate the simplicity, robustness, and feasibility of the process.