Effect of Water‐Repellent Treatment of Heating Surface on a Leidenfrost Droplet

Abstract This study investigated the flow behavior of Leidenfrost droplets on a heated plate with a hydrophobic coating. The treatment increased the contact angle from 76° to 120° and slightly enhanced surface roughness. On untreated surfaces, the evaporation time peaked at 260 °C, whereas treated surfaces showed a linear evaporation trend with a reduced Leidenfrost temperature of 140–160 °C. This suggests earlier vapor film formation due to enhanced bubble nucleation. Microscopic observation confirmed droplet levitation at 140 °C. Particle image velocimetry (PIV) analysis showed that internal flow velocity increased with temperature and was higher on treated surfaces. These results demonstrate that water‐repellent treatment lowers the Leidenfrost temperature and enhances flow, offering potential for low‐temperature droplet‐based reactions.