Dominant Role of Surface Peak-Valley Features in Droplet Infiltration Dynamics

In this study, droplet infiltration dynamics on microtextured surfaces is explored to demonstrate the dominant role of surface peak-valley features in the capillary-driven wetting process. Even though two rough surfaces have nearly the same roughness, the microtopography and distribution of surface peaks and valleys may be completely different, leading to variations in liquid infiltration characteristics. Experimental results show that under the same surface roughness (S_a = 12.0 μm), the positively skewed surface dominated by micropillars (S_sk > 0) is more conducive to liquid infiltration compared with the negatively skewed surface dominated by micropits (S_sk < 0). The physical mechanism is fully analyzed in terms of the equilibrium of the air-liquid interface by constructing a hydrodynamic model. This study also demonstrates that the dominant influence of surface peak-valley features on droplet infiltrating dynamics is independent of the materials. Moreover, the cooling efficiency of the prepared surfaces is compared, and the results indicate that the micropillar surfaces with positive skewness exhibit superior heat dissipation performance under similar conditions because of their excellent infiltration features and large spreading area, proving that positively skewed surfaces have high utilization potential in high-density heat dissipation technology.