Wrinkled micropillar surfaces inspired by moss leaves for ultrafast superspreading and cooling

Abstract

Large-area superspreading enables efficient cooling, cleaning, and liquid redistribution, yet the physical mechanisms that coordinate multi-scale surface structures with hydration conditions remain poorly defined. Here, we identify Racomitrium canescens moss leaves as a natural model that exhibits exceptional spreading performance, with fresh leaves driving water droplets to fully wet the surface in only 0.1 s, an order of magnitude faster than their dehydrated counterparts. Morphological analysis reveals a hierarchical arrangement of micrometer papillae and submicron wrinkles that suggests a multi-level wetting strategy. To elucidate this behavior, we fabricated wrinkled micropillar-arrayed surfaces (WMPS) that reproduce the essential architectural features of the moss leaves. The synthetic surfaces replicate the superspreading phenomenon, enabling a 2 μL droplet to spread completely within 0.9 s and cover an area of 160 mm² . Systematic structural decoupling demonstrates that rapid spreading arises from the synergistic action of capillary transport within the micropillar network, enhanced contact-line mobility provided by nanoscale wrinkles, and hydration-induced reduction of the surface energy barrier. In addition, the bioinspired WMPS provides effective evaporative cooling and maintains contamination resistance, reducing steady-state temperature by 6.3°C under one-sun irradiation. This work establishes a mechanistic framework for understanding hierarchical wetting and offers a scalable approach to engineering high-performance thermal-management surfaces.