Pancake bouncing and significant enhancement in Leidenfrost point on the hierarchical mesh structured surface

Abstract

The efficient cooling of hot surfaces is a long-standing challenge in various industrial fields. This is because, once the Leidenfrost phenomenon occurs, this cooling method becomes ineffective due to the presence of a stable vapor layer and significantly reduced heat transfer efficiency. Thus, increasing the critical Leidenfrost point (LFP) is a common way to maintain effective heat transfer within a wide temperature range. However, the fabrication methods in previous studies are complex and expensive. Some topological structures also lack long-term stability and the substrate material is relatively limited. In this work, we propose a superhydrophilic double-layer mesh structured surface with nanoflowers using a cost-effective manufacturing method and explore droplet dynamics at high temperatures. The pancake bouncing phenomenon and rapid detachment of droplets is observed on this superhydrophilic surface, accompanied with an obvious reduction in solid-liquid contact time, which is aroused by sufficient vapor pressure generated in the double-layer mesh structure. Moreover, such unique hierarchical surfaces can increase LFP to 410 °C, which is 78 % higher than that of the smooth surface. We further analyze the underlying mechanism responsible for LFP enhancement. Due to the improved permeability, excellent wettability and so on, the capillary pressure is increased and the vapor pressure is decreased, contributing to the complete rebound of droplets at higher critical temperatures. We speculate that the mesh structured surface coupled with high LFP can find promising applications in thermal-related fields.