Fabrication of micro/nano-hierarchical structures for droplet manipulation via velocity-controlled picosecond laser surface texturing

Surface materials with the capability of manipulating droplet play important roles in a wide range of fields from science to industry. In this work, a velocity-controlled laser surface texturing strategy was developed to fabricate micro/nano-hierarchical structures on stainless steel surface. Gradient scanning velocity method was initially used to fabricate two samples. Three typical textured zones comprising of different micro/nano-hierarchical structures were created, leading to three different wetting behaviors, i.e., superhydrophobic with low adhesion, near superhydrophobic with high adhesion and wetting with high adhesion. Subsequently, more programmable samples were created with different velocity combinations to investigate the droplet manipulation. Droplet manipulation including fast rolling, capture at designed position and direction guide sliding were successfully achieved. The velocity-controlled laser surface texturing strategy is capable of manipulating droplet on a programmable surface, which makes the strategy excellent candidate for practical applications.