Nanoscale surface effects on heterogeneous vapor bubble nucleation.

Understanding the mechanisms underlying vapor bubble nucleation on solid surfaces is critical for multiple scientific and engineering applications, such as two-phase thermal management systems and turbomachinery, among others. While classical nucleation theory (CNT) explains how surface wettability influences nucleation by modifying the free energy barrier for smooth surfaces, the interplay between nanoscale surface roughness and wettability for rough surfaces remains less clear. Using molecular dynamics simulations, this study demonstrates that CNT can accurately describe wettability effects on nucleation. In addition, we show how surface cavities can create active nucleation sites without requiring trapped gases. This occurs through spontaneous dewetting of cavities at elevated temperatures, which reduces the nucleation barrier. Our results reveal that cavity-induced nucleation enhancement depends on both wettability and geometry, with dewetting promoting nucleation on lyophobic surfaces and rewetting neutralizing this effect for more lyophilic surfaces. These findings provide insights for designing surfaces to either enhance or suppress bubble nucleation.