Dominant Role of Surface Peak–Valley Features\nin Droplet Infiltration Dynamics

In\nthis study, droplet infiltration dynamics on microtextured surfaces\nis explored to demonstrate the dominant role of surface peak–valley\nfeatures in the capillary-driven wetting process. Even though two\nrough surfaces have nearly the same roughness, the microtopography\nand distribution of surface peaks and valleys may be completely different,\nleading to variations in liquid infiltration characteristics. Experimental\nresults show that under the same surface roughness (<i>S</i><sub>a</sub> = 12.0 μm), the positively skewed surface dominated\nby micropillars (<i>S</i><sub>sk</sub> > 0) is more conducive\nto liquid infiltration compared with the negatively skewed surface\ndominated by micropits (<i>S</i><sub>sk</sub> < 0). The\nphysical mechanism is fully analyzed in terms of the equilibrium of\nthe air–liquid interface by constructing a hydrodynamic model.\nThis study also demonstrates that the dominant influence of surface\npeak–valley features on droplet infiltrating dynamics is independent\nof the materials. Moreover, the cooling efficiency of the prepared\nsurfaces is compared, and the results indicate that the micropillar\nsurfaces with positive skewness exhibit superior heat dissipation\nperformance under similar conditions because of their excellent infiltration\nfeatures and large spreading area, proving that positively skewed\nsurfaces have high utilization potential in high-density heat dissipation\ntechnology.