Measurement and analysis of solid-liquid boundary slip on surfaces with different microstructures using contact mode atomic force microscope

Surface microstructures significantly reduce fluid resistance by regulating solid-liquid boundary slip characteristics, making them an essential approach for drag reduction. This study aims to reveal the influence of hydrophobic surface structures on boundary slip length and explore the regulation of boundary slip by different micro/nanostructures. By systematically adjusting the shape, size, and arrangement of surface micro/nanostructures, the colloidal probe contact mode of atomic force microscopy is employed to measure the slip length in ionized water under varying microstructure dimensions and spacings. For square pillars with side lengths of 3, 4, 5, and 6 μm, the boundary slip lengths are 956, 1161, 1288, and 1341 nm, respectively. For cylindrical pillars with diameters of 3, 4, 5, and 6 μm, the slip lengths are 2574, 3206, 3441, and 3791 nm, respectively. Under a constant microstructure size, the slip lengths for square pillars with spacings of 2, 3, and 4 μm are 956, 2212, and 2324 nm, while for cylindrical pillars, they are 2574, 2786, and 3449 nm. The experimental results demonstrate that the shape, size, and spacing of surface microstructures have a significant effect on boundary slip length. Specifically, as the microstructure size and spacing increase, the slip length increases accordingly. Furthermore, cylindrical structures exhibit significantly higher slip lengths than square pillars under the same size and spacing conditions. These findings indicate that through rational design and optimization of microstructure geometric parameters, fluid slip behavior can be effectively controlled in microfluidic and nanofluidic applications, thereby enhancing flow efficiency and interfacial performance.